文章
Dummer. ゛☀
2017年09月19日
If your tomato plants yellow and wilt on one side of the plant or one side of a leaf, they may have Fusarium wilt. Fusarium wilt on tomatoes is caused by Fusarium oxysporumsp. lycopersici. It is a soilborn fungus that is found throughout the United States, especially in warm regions of the country. The organism is specific for tomato and is very longlived in all regions of the United States. The disease develops more quickly in soils that are high in nitrogen and low in potassium. In addition, plants grown in sandy soils tend to contract this disease more often.
Symptoms and Diagnosis
Fusarium often causes yellowing on one side of the plant or leaf. Yellowing begins with the older, bottom leaves, followed by wilting, browning, and defoliation. Growth is typically stunted, and little or no fruit develops. Brown, vascular tissue can be found when the infected stem is cut at its base. Infected plants often die before maturing.
Life Cycle
Fusarium fungi survive in the soil or associated with plant debris for up to ten years. Disease development is favored by warm soil temperatures, and symptoms are most prevalent when temperatures range from 80–90 degrees F. The fungi enter the plants through their roots and are then spread throughout the plant by the plant's water-conducting vessels.
Integrated Pest Management Strategies
1. Plant resistant varieties. These varieties are labeled VF and include cultivars such as ‘Spring Giant’, ‘Burpee VF’, ‘Supersonic’, ‘Celebrity’, ‘Manalucie’, ‘Better Boy’, and ‘Small Fry’.
2. Remove infected plants from the garden. Removal of infected plants will help limit the disease's spread. Soil sterilization or fumigation will eliminate wilt fungi from the soil but are impractical for home gardeners. Soil replacement should be considered.
3. Avoid over-application of high nitrogen fertilizers. High soil nitrogen levels accompanied by low potassium levels can increase susceptibility to the fungus. Use a soil test to determine potassium levels and other nutrient deficiencies.
4. Avoid activity in wet plantings. Movement of wet soil from place to place via shoes or tools will spread the disease.
5. Sanitize stakes and tomato cages at the end of the season. Avoid using soil-encrusted tools and supports season after season. A thorough cleaning with water will reduce most risk of transmitting the disease.
6. For four years, do not plant solanaceous plants in the area where infection occurred. Tomato, potato, pepper, and eggplant are all susceptible to the disease and may allow its survival year after year in the same planting area.
Symptoms and Diagnosis
Fusarium often causes yellowing on one side of the plant or leaf. Yellowing begins with the older, bottom leaves, followed by wilting, browning, and defoliation. Growth is typically stunted, and little or no fruit develops. Brown, vascular tissue can be found when the infected stem is cut at its base. Infected plants often die before maturing.
Life Cycle
Fusarium fungi survive in the soil or associated with plant debris for up to ten years. Disease development is favored by warm soil temperatures, and symptoms are most prevalent when temperatures range from 80–90 degrees F. The fungi enter the plants through their roots and are then spread throughout the plant by the plant's water-conducting vessels.
Integrated Pest Management Strategies
1. Plant resistant varieties. These varieties are labeled VF and include cultivars such as ‘Spring Giant’, ‘Burpee VF’, ‘Supersonic’, ‘Celebrity’, ‘Manalucie’, ‘Better Boy’, and ‘Small Fry’.
2. Remove infected plants from the garden. Removal of infected plants will help limit the disease's spread. Soil sterilization or fumigation will eliminate wilt fungi from the soil but are impractical for home gardeners. Soil replacement should be considered.
3. Avoid over-application of high nitrogen fertilizers. High soil nitrogen levels accompanied by low potassium levels can increase susceptibility to the fungus. Use a soil test to determine potassium levels and other nutrient deficiencies.
4. Avoid activity in wet plantings. Movement of wet soil from place to place via shoes or tools will spread the disease.
5. Sanitize stakes and tomato cages at the end of the season. Avoid using soil-encrusted tools and supports season after season. A thorough cleaning with water will reduce most risk of transmitting the disease.
6. For four years, do not plant solanaceous plants in the area where infection occurred. Tomato, potato, pepper, and eggplant are all susceptible to the disease and may allow its survival year after year in the same planting area.
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文章
Dummer. ゛☀
2017年09月19日
Sycamore anthracnose is a fungal disease that can cause leaf drop, twig dieback, cankers and the sudden death of more than 90% of a tree’s new shoot growth. Although the disease is rarely fatal and trees will grow a second set of leaves, repeat infections will result in abnormal branching and will leave a tree stressed and more susceptible to other diseases and pests. American sycamore or buttonwood (Platanus occidentalis), London plane tree (P. x acerifolia) and Oriental plane tree (P. orientalis) may all be affected by sycamore anthracnose.
Symptoms and Diagnosis
Sycamore anthracnose is most common during the cool wet weather of spring and is often mistaken for frost damage. As new leaves unfold, they crinkle and turn brown, wilt rapidly and fall. Dark and sunken dead areas form along the veins of older leaves eventually expanding to include the entire leaf. The tree may also develop cankers on twigs and older branches resulting in twig dieback and the girdling and death of the larger branches. Small black dots, the fruiting bodies of the fungus, may be visible. The clusters of dead twigs will result in abnormal branching such as witches’ brooms or as the twigs die, break and fall, the tree will appear ragged. Reportedly, London plane tree is less susceptible to cankers than the American sycamore.
Life Cycle
The sycamore anthracnose fungus, Apiognomonia veneta, overwinters in diseased leaves and in cankers on twigs and branches. Spores are produced in spring and spread by rain. If the mean daily temperatures are 50 – 55 degrees F., the spores will germinate and the resulting infections will cause the death of new buds, shoots and leaves. The disease will be slight or will not occur by late spring or midsummer when the mean daily temperatures are 60 degrees F. or greater and the tree will be able to produce a second set of leaves. The fungus may also infect twigs and buds in fall after leaf drop.
Integrated Pest Management Strategies
1. Be patient. The tree may appear to be dead but will probably recover and develop new leaves and shoots.
2. Practice good garden sanitation by raking up and disposing of fallen leaves and twigs.
3. Practice good cultural techniques to keep plants healthy and free of drought, nutritional or injury-induced stress. Water trees twice a month during dry winters.
4. Prune out dead branches when possible. Disinfect pruning shears in a 10% bleach solution between cuts to avoid spreading the disease.
5. Prune branches to improve air circulation reducing the length of time leaves are wet and thus susceptible to infection.
6. Treat with a preventive systemic fungicide. This treatment may require the services of a certified arborist.
7. Spray with a preventive fungicide such as lime-sulfur (Bordeaux mixture) or chlorothalonil (daconil) when leaves begin to emerge from buds. Reapply two or three more times at 7-10 day intervals. Fungicides are not effective after the leaves have been infected. Large trees may require the services of a certified arborist.
8. Plant resistant species or cultivars. Oriental plane tree (zones 7-9) and London plane tree cultivars, ‘Bloodgood’, ‘Columbia’ and ‘Liberty’ are less susceptible to the disease than the American sycamore.
Symptoms and Diagnosis
Sycamore anthracnose is most common during the cool wet weather of spring and is often mistaken for frost damage. As new leaves unfold, they crinkle and turn brown, wilt rapidly and fall. Dark and sunken dead areas form along the veins of older leaves eventually expanding to include the entire leaf. The tree may also develop cankers on twigs and older branches resulting in twig dieback and the girdling and death of the larger branches. Small black dots, the fruiting bodies of the fungus, may be visible. The clusters of dead twigs will result in abnormal branching such as witches’ brooms or as the twigs die, break and fall, the tree will appear ragged. Reportedly, London plane tree is less susceptible to cankers than the American sycamore.
Life Cycle
The sycamore anthracnose fungus, Apiognomonia veneta, overwinters in diseased leaves and in cankers on twigs and branches. Spores are produced in spring and spread by rain. If the mean daily temperatures are 50 – 55 degrees F., the spores will germinate and the resulting infections will cause the death of new buds, shoots and leaves. The disease will be slight or will not occur by late spring or midsummer when the mean daily temperatures are 60 degrees F. or greater and the tree will be able to produce a second set of leaves. The fungus may also infect twigs and buds in fall after leaf drop.
Integrated Pest Management Strategies
1. Be patient. The tree may appear to be dead but will probably recover and develop new leaves and shoots.
2. Practice good garden sanitation by raking up and disposing of fallen leaves and twigs.
3. Practice good cultural techniques to keep plants healthy and free of drought, nutritional or injury-induced stress. Water trees twice a month during dry winters.
4. Prune out dead branches when possible. Disinfect pruning shears in a 10% bleach solution between cuts to avoid spreading the disease.
5. Prune branches to improve air circulation reducing the length of time leaves are wet and thus susceptible to infection.
6. Treat with a preventive systemic fungicide. This treatment may require the services of a certified arborist.
7. Spray with a preventive fungicide such as lime-sulfur (Bordeaux mixture) or chlorothalonil (daconil) when leaves begin to emerge from buds. Reapply two or three more times at 7-10 day intervals. Fungicides are not effective after the leaves have been infected. Large trees may require the services of a certified arborist.
8. Plant resistant species or cultivars. Oriental plane tree (zones 7-9) and London plane tree cultivars, ‘Bloodgood’, ‘Columbia’ and ‘Liberty’ are less susceptible to the disease than the American sycamore.
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文章
Dummer. ゛☀
2017年09月19日
Oak leaf blister (oak leaf curl) is a fungal leaf disease caused by the fungus Taphrina caerulescens. Circular, raised areas ranging up to 2 inches in diameter are scattered over the upper leaf surface. During cool wet springs, almost all species of oak are subject to the leaf blister disease. Members of the red oak family are particularly susceptible to infection. The disease is closely related to Taprina deformans which causes peach leaf curl.
Symptoms and Diagnosis
Blister-like, circular, raised areas appear scattered on the upper leaf surface. This raised area causes a corresponding depression on the lower leaf surface at the same site and of the same size. The color of the upper convex area is yellowish white while the bottom concave area is yellowish brown.
Leaves with numerous spots may fall prematurely to the ground. If well-established trees defoliate before midsummer, they will sometimes leaf out later in the season. When defoliation occurs in late summer, leaf loss will have little impact on the overall health of the tree.
Life Cycle
During mid-spring, microscopic spores are produced in leaf spots. These spores are carried by wind and splashing raindrops onto bud scales and twigs where they remain in a dormant stage until the following early spring. At this time, rain washes the spores onto young leaves where infection takes place. Depending on weather conditions, small circular spots begin to develop in 2 to 4 weeks. Spores produced on these spots will lodge in bud scales and again remain resting until the following spring. Cool wet weather is required for germination on young leaves, and if these conditions continue, severe infection can occur. If weather conditions are not favorable for spore germination shortly after bud break, only minor infection will occur. As the leaves mature, they become more resistant to infection.
Integrated Pest Management Strategies
1. Maintain plant vigor. Keep the tree well watered during drought conditions (approximately 1 inch of water per week) and well-drained during periods of heavy rain. Fertilize according to soil test recommendations. Apply nitrogen every 3 to 5 years for mature shade trees.
2. General health. Oak leaf blister does not seriously affect the overall health of the tree unless the tree is repeatedly defoliated in successive years. Even if this occurs, the second set of leaves should emerge at a time when conditions are not conducive to reinfection of leaves and newly formed bud scales.
3. Fungicides. A single application of a fungicide applied in the spring at the time of bud-swelling is usually adequate. Apply with a power sprayer and coat buds and twigs thoroughly for good control. chlorothalonil (Daconil) is currently registered for use in controlling oak leaf blister. Fungicides will not be effective if applied after bud break. As with the use of all chemicals, carefully read and follow the manufacturer’s directions.
Symptoms and Diagnosis
Blister-like, circular, raised areas appear scattered on the upper leaf surface. This raised area causes a corresponding depression on the lower leaf surface at the same site and of the same size. The color of the upper convex area is yellowish white while the bottom concave area is yellowish brown.
Leaves with numerous spots may fall prematurely to the ground. If well-established trees defoliate before midsummer, they will sometimes leaf out later in the season. When defoliation occurs in late summer, leaf loss will have little impact on the overall health of the tree.
Life Cycle
During mid-spring, microscopic spores are produced in leaf spots. These spores are carried by wind and splashing raindrops onto bud scales and twigs where they remain in a dormant stage until the following early spring. At this time, rain washes the spores onto young leaves where infection takes place. Depending on weather conditions, small circular spots begin to develop in 2 to 4 weeks. Spores produced on these spots will lodge in bud scales and again remain resting until the following spring. Cool wet weather is required for germination on young leaves, and if these conditions continue, severe infection can occur. If weather conditions are not favorable for spore germination shortly after bud break, only minor infection will occur. As the leaves mature, they become more resistant to infection.
Integrated Pest Management Strategies
1. Maintain plant vigor. Keep the tree well watered during drought conditions (approximately 1 inch of water per week) and well-drained during periods of heavy rain. Fertilize according to soil test recommendations. Apply nitrogen every 3 to 5 years for mature shade trees.
2. General health. Oak leaf blister does not seriously affect the overall health of the tree unless the tree is repeatedly defoliated in successive years. Even if this occurs, the second set of leaves should emerge at a time when conditions are not conducive to reinfection of leaves and newly formed bud scales.
3. Fungicides. A single application of a fungicide applied in the spring at the time of bud-swelling is usually adequate. Apply with a power sprayer and coat buds and twigs thoroughly for good control. chlorothalonil (Daconil) is currently registered for use in controlling oak leaf blister. Fungicides will not be effective if applied after bud break. As with the use of all chemicals, carefully read and follow the manufacturer’s directions.
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文章
Dummer. ゛☀
2017年09月19日
Cornus species are riddled with leaf diseases. After the discovery of dogwood anthracnose that devastated the dogwood population in the northeastern U.S., it has been increasingly more significant to be on alert for disease outbreaks. Three leaf spot diseases that show themselves in varying degrees are dogwood anthracnose, spot anthracnose, and powdery mildew. Dogwood anthracnose and powdery mildew are of particular concern. Dogwood anthracnose was confirmed in St. Louis in 2012 and again in 2015. Powdery mildew can occur yearly.
Symptoms and Diagnosis
Symptoms of Dogwood Anthracnose: Dogwood anthracnose is a disease caused by the fungus, Discula destructiva. Since its discovery in the 1970s, the spread has been swift and the results disastrous to the native Cornus florida. Symptoms include leaf spots that are soft and very wet with purple borders, twig blight, dead leaves that cling to the tree, epicormic shoots (water sprouts with many shoots occurring near the base of the tree), lower branch dieback, and eventually death. Conditions that favor disease include low light levels, high humidity, and temperatures of 60 F. In the St. Louis area it was found in the Kirkwood/Ladue area in 2012 and the Brentwood area in 2015. It is considered established in St. Louis.
Symptoms of Spot Anthracnose: Spot anthracnose is caused by the fungus, Elsinoe corni. Symptoms include small, dark, pinprick lesions with purple borders on leaf surfaces. The lesions are numerous and usually occur on dry leaves. The disease is unsightly, but typically not very harmful.
Symptoms of Powdery Mildew: Powdery mildew is caused by the fungus, Microsphaera pulchra. Early symptoms include round, white or gray powder-like spots that appear on upper leaf surfaces. These spots form a dry white layer on leaves. As young leaves become infected, they appear twisted, dry, and leathery. Older leaves look bronzed. Moderate temperatures, low light, and high humidity accelerate this disease. High nitrogen levels cause the disease to flourish.
Integrated Pest Management Strategies
1. Choose disease resistant varieties. A soon-to-be released cultivar for dogwood anthracnose resistance is called ‘Appalachian Spring’. Cultivars less susceptible to spot anthracnose include ‘Cherokee Princess’, ‘Cherokee Sunset’, and ‘Springtime’. ‘Cherokee Brave’, C. kousa, and C. kousa x C. florida crosses are resistant to powdery mildew.
2. Water the roots of the tree. Avoid using overhead irrigation in order to reduce the incidence of leaf spot.
3. Practice good sanitation. Promptly remove and dispose of any dead or dying twigs or branches found in trees as well as leaves that show the symptoms of dogwood anthracnose. Leaves with spot anthrancnose and powdery mildew can remain but rake and remove them in the fall when they drop.
4. Remove plants confirmed with dogwood anthracnose. Removing an infected tree confirmed with dogwood anthracnose is strongly recommended. The infected trees should NOT be converted to mulch to avoid spreading the disease.
5. Apply fungicides. If you suspect dogwood anthracnose, get it diagnosed by a professional prior to a fungicide application. Powdery mildew should also be controlled, especially if the disease has occurred previously.
Symptoms and Diagnosis
Symptoms of Dogwood Anthracnose: Dogwood anthracnose is a disease caused by the fungus, Discula destructiva. Since its discovery in the 1970s, the spread has been swift and the results disastrous to the native Cornus florida. Symptoms include leaf spots that are soft and very wet with purple borders, twig blight, dead leaves that cling to the tree, epicormic shoots (water sprouts with many shoots occurring near the base of the tree), lower branch dieback, and eventually death. Conditions that favor disease include low light levels, high humidity, and temperatures of 60 F. In the St. Louis area it was found in the Kirkwood/Ladue area in 2012 and the Brentwood area in 2015. It is considered established in St. Louis.
Symptoms of Spot Anthracnose: Spot anthracnose is caused by the fungus, Elsinoe corni. Symptoms include small, dark, pinprick lesions with purple borders on leaf surfaces. The lesions are numerous and usually occur on dry leaves. The disease is unsightly, but typically not very harmful.
Symptoms of Powdery Mildew: Powdery mildew is caused by the fungus, Microsphaera pulchra. Early symptoms include round, white or gray powder-like spots that appear on upper leaf surfaces. These spots form a dry white layer on leaves. As young leaves become infected, they appear twisted, dry, and leathery. Older leaves look bronzed. Moderate temperatures, low light, and high humidity accelerate this disease. High nitrogen levels cause the disease to flourish.
Integrated Pest Management Strategies
1. Choose disease resistant varieties. A soon-to-be released cultivar for dogwood anthracnose resistance is called ‘Appalachian Spring’. Cultivars less susceptible to spot anthracnose include ‘Cherokee Princess’, ‘Cherokee Sunset’, and ‘Springtime’. ‘Cherokee Brave’, C. kousa, and C. kousa x C. florida crosses are resistant to powdery mildew.
2. Water the roots of the tree. Avoid using overhead irrigation in order to reduce the incidence of leaf spot.
3. Practice good sanitation. Promptly remove and dispose of any dead or dying twigs or branches found in trees as well as leaves that show the symptoms of dogwood anthracnose. Leaves with spot anthrancnose and powdery mildew can remain but rake and remove them in the fall when they drop.
4. Remove plants confirmed with dogwood anthracnose. Removing an infected tree confirmed with dogwood anthracnose is strongly recommended. The infected trees should NOT be converted to mulch to avoid spreading the disease.
5. Apply fungicides. If you suspect dogwood anthracnose, get it diagnosed by a professional prior to a fungicide application. Powdery mildew should also be controlled, especially if the disease has occurred previously.
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文章
Dummer. ゛☀
2017年09月19日
Leaf spot is a common descriptive term applied to a number of diseases affecting the foliage of ornamentals and shade trees. The majority of leaf spots are caused by fungi, but some are caused by bacteria. Some insects also cause damage that appears like a leaf spot disease. Leaf spots on trees are very common and generally do not require spraying. Leaf spot may result in some defoliation of a plant. An established plant can tolerate almost complete defoliation if it happens late in the season or not every year. Small or newly planted trees that become defoliated are more at risk of suffering damage until they become established.
Symptoms and Diagnosis
The chief symptom of a leaf spot disease is spots on foliage. The spots will vary in size and color depending on the plant affected, the specific organism involved, and the stage of development. Spots are most often brownish, but may be tan or black. Concentric rings or dark margins are often present. Fungal bodies may appear as black dots in the spots, either in rings or in a central cluster. Over time, the spots may combine or enlarge to form blotches. Spots or blotches that are angular are generally referred to as anthracnose (see entry on “Anthracnose of Trees”) Leaves may yellow and drop prematurely.
Life Cycle
The organisms that cause leaf spots survive in fallen infected leaves and twigs. Some may remain in dead twigs on the tree. Most damage occurs in spring. During wet weather, spores may splash or be windblown onto newly emerging tender leaves where they germinate in the moisture and infect the leaf. Overhead watering can also provide prolonged wet periods that are ideal for spreading leaf spot diseases.
Integrated Pest Management Strategies
1. Live with the disease. Most trees tolerate leaf spots with little or no apparent damage. A tree affected early in the year will re-leaf and the new leaves may not be affected. Only if defoliation occurs three or more years in a row will most established plants be adversely affected.
2. Remove infected leaves and dead twigs. Raking up and disposing of infected leaves as they drop and pruning out dead twigs can help control the disease by removing spores that can reinfect the new leaves. This is not a cure but may help limit infection by reducing the total amount of inoculum.
3. Keep foliage dry. Avoid overhead watering. Use soaker hoses or water early in the day so the foliage can dry off before night. Watering can also spread the disease by splashing. Pruning plants to allow for good air circulation and reducing crowding will also help keep the foliage dry.
4. Keep plants healthy. Since most plants can tolerate some defoliation, keep them in good health so they can rebound quickly. Avoid over fertilizing by testing the soil first. Abundant, young, tender growth is very susceptible to attack by disease and insects. Overuse of nitrogen can cause an abundance of succulent growth.
5. Use fungicides if needed. In rare cases of severe infection and where the size and value of plants make it practicable, applications of fungicides may be helpful. Sprays will not cure infected leaves. Therefore, once the damage is noticed, spraying may have limited value. Spraying generally needs to be started as buds break in the spring and repeated at 10–14 day intervals. Recommendations will vary by disease and fungicide used. Have the disease identified before purchasing a control product.
6. Replace the plant. Though a drastic measure, many gardeners find it less bother and more rewarding to replace a plant that is continually plagued with leaf spot diseases. Either replace with a different kind of plant or a variety that is more resistant or tolerant of disease. A nursery can help you in your selection.
Symptoms and Diagnosis
The chief symptom of a leaf spot disease is spots on foliage. The spots will vary in size and color depending on the plant affected, the specific organism involved, and the stage of development. Spots are most often brownish, but may be tan or black. Concentric rings or dark margins are often present. Fungal bodies may appear as black dots in the spots, either in rings or in a central cluster. Over time, the spots may combine or enlarge to form blotches. Spots or blotches that are angular are generally referred to as anthracnose (see entry on “Anthracnose of Trees”) Leaves may yellow and drop prematurely.
Life Cycle
The organisms that cause leaf spots survive in fallen infected leaves and twigs. Some may remain in dead twigs on the tree. Most damage occurs in spring. During wet weather, spores may splash or be windblown onto newly emerging tender leaves where they germinate in the moisture and infect the leaf. Overhead watering can also provide prolonged wet periods that are ideal for spreading leaf spot diseases.
Integrated Pest Management Strategies
1. Live with the disease. Most trees tolerate leaf spots with little or no apparent damage. A tree affected early in the year will re-leaf and the new leaves may not be affected. Only if defoliation occurs three or more years in a row will most established plants be adversely affected.
2. Remove infected leaves and dead twigs. Raking up and disposing of infected leaves as they drop and pruning out dead twigs can help control the disease by removing spores that can reinfect the new leaves. This is not a cure but may help limit infection by reducing the total amount of inoculum.
3. Keep foliage dry. Avoid overhead watering. Use soaker hoses or water early in the day so the foliage can dry off before night. Watering can also spread the disease by splashing. Pruning plants to allow for good air circulation and reducing crowding will also help keep the foliage dry.
4. Keep plants healthy. Since most plants can tolerate some defoliation, keep them in good health so they can rebound quickly. Avoid over fertilizing by testing the soil first. Abundant, young, tender growth is very susceptible to attack by disease and insects. Overuse of nitrogen can cause an abundance of succulent growth.
5. Use fungicides if needed. In rare cases of severe infection and where the size and value of plants make it practicable, applications of fungicides may be helpful. Sprays will not cure infected leaves. Therefore, once the damage is noticed, spraying may have limited value. Spraying generally needs to be started as buds break in the spring and repeated at 10–14 day intervals. Recommendations will vary by disease and fungicide used. Have the disease identified before purchasing a control product.
6. Replace the plant. Though a drastic measure, many gardeners find it less bother and more rewarding to replace a plant that is continually plagued with leaf spot diseases. Either replace with a different kind of plant or a variety that is more resistant or tolerant of disease. A nursery can help you in your selection.
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文章
Dummer. ゛☀
2017年09月19日
Bacterial leaf scorch (BLS) is a systemic disease caused by the bacterium Xylella fastidiosa, which invades the xylem (water and nutrient conducting tissues) of susceptible trees. It is most commonly seen in pin, red, shingle, bur, and white oaks, but can also affect elm, oak, sycamore, mulberry, sweetgum, sugar maple, and red maple. Xylem-feeding leafhoppers and spittlebugs spread the bacterium from tree to tree. Transmission between trees through root grafts has also been reported. There is no cure for this disease; it is chronic and potentially fatal.
Symptoms and Diagnosis
The first noticeable symptom is premature browning of leaves in mid-summer. Symptoms worsen throughout late summer and fall. Leaf margins turn brown, beginning with the older leaves and moving outward, spreading to leaves toward the branch tip. In most, but not all infected trees, browned, dead areas of the leaf are separated from green tissue by a narrow yellow border. The browned leaves may drop from the tree. Infected trees leaf-out normally the following year, with leaves on a few more branches turning prematurely brown in late summer. Symptoms become progressively worse over a period of 3 to 8 years, until the entire tree turns brown prematurely. The lack of green, chlorophyll producing leaves year after year leads to twig, branch, and limb death due to continual defoliation.
Bacterial leaf scorch can easily be mistaken for oak wilt or Dutch elm disease, except for the following:
The cycle of bacterial leaf scorch repeats and becomes worse over a long period of time. Oak wilt and Dutch elm disease are both capable of killing susceptible trees within a matter of months.
There is no streaking of the sapwood with bacterial leaf scorch.
In bacterial leaf scorch, the leaf browning develops from the leaf edges and works toward the mid-vein, whereas browning tends to happen in a more overall, uniform manner with oak wilt and Dutch elm disease.
Bacterial leaf scorch can also be mistaken for drought and heat stress. However, damage by bacterial leaf scorch begins in old leaves and spreads to the branch tips, with browning around the leaf edges. Damage due to environmental stresses tends to cause overall browning to the canopy and to individual leaves. Trees tend to react to environmental stress soon after damaging conditions occur whereas bacterial leaf scorch is unique in its timing. Leaf browning is generally not noticed until mid-summer and intensifies through late summer and fall.
The only way to confirm the diagnosis of bacterial leaf scorch is through laboratory analysis. This can be done by sending a sample to the MU Extension Plant Diagnostic Clinic. The best time to test for the presence of this disease is in late summer or early fall, when the bacteria count is at its highest.
Life Cycle
Infected leafhoppers and spittlebugs feed on the succulent, terminal shoots of susceptible host trees, transmitting the bacteria. Xylem vessels become clogged with bacterium as it travels within, multiplying and infecting other parts of the tree. There are no viable control options for the insect vectors. The cold-sensitive bacteria overwinter in protected areas within the xylem of the tree, and their populations begin to climb again as the next growing season progresses.
Integrated Pest Management Strategies
1. Maintain plant vigor. There is no cure for the disease. Keeping susceptible trees healthy and thriving can help them resist infection and survive longer once they are infected.
2. Practice good sanitation. Branches that have died due to bacterial leaf scorch should be routinely removed. Infected trees that are in a severe state of decline should also be removed. Disinfect pruning tools with a 10% bleach solution between pruning cuts.
3. Plant resistant species. In areas where bacterial leaf scorch has occurred, avoid planting highly susceptible trees.
4. Antibiotic injections. Oxytetracycline root flare injections applied in spring can reduce bacterium levels and delay symptoms by a couple of weeks. They are expensive, need to be reapplied each year, and possible damage resulting from long-term use is unknown. A certified arborist should be contacted if you are considering injections.
Symptoms and Diagnosis
The first noticeable symptom is premature browning of leaves in mid-summer. Symptoms worsen throughout late summer and fall. Leaf margins turn brown, beginning with the older leaves and moving outward, spreading to leaves toward the branch tip. In most, but not all infected trees, browned, dead areas of the leaf are separated from green tissue by a narrow yellow border. The browned leaves may drop from the tree. Infected trees leaf-out normally the following year, with leaves on a few more branches turning prematurely brown in late summer. Symptoms become progressively worse over a period of 3 to 8 years, until the entire tree turns brown prematurely. The lack of green, chlorophyll producing leaves year after year leads to twig, branch, and limb death due to continual defoliation.
Bacterial leaf scorch can easily be mistaken for oak wilt or Dutch elm disease, except for the following:
The cycle of bacterial leaf scorch repeats and becomes worse over a long period of time. Oak wilt and Dutch elm disease are both capable of killing susceptible trees within a matter of months.
There is no streaking of the sapwood with bacterial leaf scorch.
In bacterial leaf scorch, the leaf browning develops from the leaf edges and works toward the mid-vein, whereas browning tends to happen in a more overall, uniform manner with oak wilt and Dutch elm disease.
Bacterial leaf scorch can also be mistaken for drought and heat stress. However, damage by bacterial leaf scorch begins in old leaves and spreads to the branch tips, with browning around the leaf edges. Damage due to environmental stresses tends to cause overall browning to the canopy and to individual leaves. Trees tend to react to environmental stress soon after damaging conditions occur whereas bacterial leaf scorch is unique in its timing. Leaf browning is generally not noticed until mid-summer and intensifies through late summer and fall.
The only way to confirm the diagnosis of bacterial leaf scorch is through laboratory analysis. This can be done by sending a sample to the MU Extension Plant Diagnostic Clinic. The best time to test for the presence of this disease is in late summer or early fall, when the bacteria count is at its highest.
Life Cycle
Infected leafhoppers and spittlebugs feed on the succulent, terminal shoots of susceptible host trees, transmitting the bacteria. Xylem vessels become clogged with bacterium as it travels within, multiplying and infecting other parts of the tree. There are no viable control options for the insect vectors. The cold-sensitive bacteria overwinter in protected areas within the xylem of the tree, and their populations begin to climb again as the next growing season progresses.
Integrated Pest Management Strategies
1. Maintain plant vigor. There is no cure for the disease. Keeping susceptible trees healthy and thriving can help them resist infection and survive longer once they are infected.
2. Practice good sanitation. Branches that have died due to bacterial leaf scorch should be routinely removed. Infected trees that are in a severe state of decline should also be removed. Disinfect pruning tools with a 10% bleach solution between pruning cuts.
3. Plant resistant species. In areas where bacterial leaf scorch has occurred, avoid planting highly susceptible trees.
4. Antibiotic injections. Oxytetracycline root flare injections applied in spring can reduce bacterium levels and delay symptoms by a couple of weeks. They are expensive, need to be reapplied each year, and possible damage resulting from long-term use is unknown. A certified arborist should be contacted if you are considering injections.
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Dummer. ゛☀
2017年09月19日
Anthracnose is a group of related fungal leaf and stem diseases that infect shade trees. Maple anthracnose is not the same disease as oak anthracnose, although the symptoms of these diseases may be quite similar. Anthracnose diseases generally infect the leaf veins and cause death of the vein and surrounding tissue. Control of anthracnose diseases follows the same procedure for all shade trees affected. The disease does not cause the death of the host but may reduce growth over successive seasons of complete defoliation.
Symptoms and Diagnosis
Irregular, light brown spots of dead tissue develop along the veins of the leaves. Affected plants may have the appearance of being sun-scorched. Sunken cankers containing fungal spores develop on infected twigs of some trees, such as sycamore.
Life Cycle
Anthracnose fungi overwinter on fallen leaves and twigs that were infected the proceeding year. Infection is favored by cool, moist weather in the spring of the year. Infection can occur on the vulnerable young leaves when there is a film of water on the leaf surface. Infection is typically more severe on the lower third of the tree, where the humidity is the highest.
Integrated Pest Management Strategies
1. Collect and destroy infected leaves as they fall. Infected leaves and twigs that remain in the vicinity are a source of spores for new infections in the spring.
2. Prune out dead branches. Be sure to clean all garden tools to avoid the spread of the disease. A 1–part bleach to 9–part water solution can be used to dip tools into between cuts.
3. Promote air circulation. Thin out excessive twig and branch growth. This will reduce the period of time that leaves are wet and vulnerable to inoculation.
4. Keep trees growing vigorously. Supply 1–2 inches of water weekly only during dry periods. Fertilize early in the spring or in late fall.
5. Spray with a fungicide when leaves are beginning to enlarge from the buds. Reapply at 7–10 day intervals for two or three more times. Fungicide sprays are most appropriate for younger, newly transplanted trees that may not be able to withstand defoliation. The available fungicides are preventive, not curative, and therefore, must be applied before spotting occurs. Commonly used products include copper, chlorothalonil (Daconil), captan, ferbam, mancozeb, maneb, and thiram. Your pesticide choice should be based on the particular problem you are seeking to control. Consult an arborist for difficult situations and where power equipment is required.
Symptoms and Diagnosis
Irregular, light brown spots of dead tissue develop along the veins of the leaves. Affected plants may have the appearance of being sun-scorched. Sunken cankers containing fungal spores develop on infected twigs of some trees, such as sycamore.
Life Cycle
Anthracnose fungi overwinter on fallen leaves and twigs that were infected the proceeding year. Infection is favored by cool, moist weather in the spring of the year. Infection can occur on the vulnerable young leaves when there is a film of water on the leaf surface. Infection is typically more severe on the lower third of the tree, where the humidity is the highest.
Integrated Pest Management Strategies
1. Collect and destroy infected leaves as they fall. Infected leaves and twigs that remain in the vicinity are a source of spores for new infections in the spring.
2. Prune out dead branches. Be sure to clean all garden tools to avoid the spread of the disease. A 1–part bleach to 9–part water solution can be used to dip tools into between cuts.
3. Promote air circulation. Thin out excessive twig and branch growth. This will reduce the period of time that leaves are wet and vulnerable to inoculation.
4. Keep trees growing vigorously. Supply 1–2 inches of water weekly only during dry periods. Fertilize early in the spring or in late fall.
5. Spray with a fungicide when leaves are beginning to enlarge from the buds. Reapply at 7–10 day intervals for two or three more times. Fungicide sprays are most appropriate for younger, newly transplanted trees that may not be able to withstand defoliation. The available fungicides are preventive, not curative, and therefore, must be applied before spotting occurs. Commonly used products include copper, chlorothalonil (Daconil), captan, ferbam, mancozeb, maneb, and thiram. Your pesticide choice should be based on the particular problem you are seeking to control. Consult an arborist for difficult situations and where power equipment is required.
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Dummer. ゛☀
2017年09月19日
Algal leaf spot is a foliar disease most commonly seen in warm humid climates or in greenhouses. The causal organism is Cephaleuros virescens, a green parasitic alga whose usual hosts are plants with leathery leaves such as cotoneasters, magnolias, hollies, rhododendrons and viburnums. Algal leaf spot is sometimes called green scurf because the spots may have a crusty, fuzzy or flaky appearance.
Symptoms and Diagnosis
Algal leaf spot is characterized by grayish, green, brown or orange cushion-like blotches on the leaf surface. Some hosts may also have diseased twigs and branches that are girdled and stunted with reddish brown fruiting bodies. The spots are generally 1/2 inch or less in diameter although they may coalesce to form larger colonies. Leaf tissue may die beneath the spots and the leaves may yellow and drop prematurely.
Life Cycle
During wet weather, the algae produce spores that are spread by wind and splashing rain. The spores infect leaf tissue causing small, greenish circular spots that may age to light brown or reddish brown. The spots may appear raised and velvety. The algae will overwinter or survive other unfavorable environmental conditions in leaf spots including those on fallen leaves.
Integrated Pest Management Strategies
1. Encourage healthy plants with good cultural techniques. This disease is most damaging on plants that are already slow-growing or weakened.
2. Clean up fallen leaves and remove diseased leaves from the plant. Good sanitation practices will help control this disease.
3. Promote dry leaves by improving air circulation and drainage. If necessary, selectively prune overcrowded vegetation. Avoid spraying water on the leaves.
4. Use fungicidal sprays containing copper if chemical control is necessary
Symptoms and Diagnosis
Algal leaf spot is characterized by grayish, green, brown or orange cushion-like blotches on the leaf surface. Some hosts may also have diseased twigs and branches that are girdled and stunted with reddish brown fruiting bodies. The spots are generally 1/2 inch or less in diameter although they may coalesce to form larger colonies. Leaf tissue may die beneath the spots and the leaves may yellow and drop prematurely.
Life Cycle
During wet weather, the algae produce spores that are spread by wind and splashing rain. The spores infect leaf tissue causing small, greenish circular spots that may age to light brown or reddish brown. The spots may appear raised and velvety. The algae will overwinter or survive other unfavorable environmental conditions in leaf spots including those on fallen leaves.
Integrated Pest Management Strategies
1. Encourage healthy plants with good cultural techniques. This disease is most damaging on plants that are already slow-growing or weakened.
2. Clean up fallen leaves and remove diseased leaves from the plant. Good sanitation practices will help control this disease.
3. Promote dry leaves by improving air circulation and drainage. If necessary, selectively prune overcrowded vegetation. Avoid spraying water on the leaves.
4. Use fungicidal sprays containing copper if chemical control is necessary
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文章
Dummer. ゛☀
2017年09月18日
Poison ivy, Toxicodendron radicans, is usually a vine twining on trees and occasionally an upright bush if there is no support. Each leaf is made up of three leaflets more or less notched at the edges. Two of the leaflets form a pair on opposite sides of the leafstalk, while the third leaflet stands by itself at the tip of the leafstalk. Small greenish flowers grow in bunches attached to the main stem close to the point where each leaf joins it. Later in the season, clusters of poisonous, berry-like drupes form. They are a dirty yellowish-white, waxy berry similar to mistletoe. The leaves are red in early spring becoming shiny green in summer and then turning red or orange in autumn.
Integrated Pest Management Strategies
1. Pull small plants. If only a few small plants are found, pull and dispose of the plants using rubber gloves and arm protection. Avoid touching the leaves. Dispose of the plants in a plastic bag so they will not be touched by others. All parts of the plant are toxic. NEVER BURN THE PLANTS. The fumes are as toxic as touching the plant and worse if inhaled.
2. Use herbicides. For small areas, poison ivy killers available in aerosol cans may be a good choice. They are effective and convenient but are too expensive for treating large areas.
Another option is to use glyphosate (Roundup, Kleenup). Spray the leaves of actively growing plants taking care to protect nearby desirable plants from spray drift which can damage or kill them. Leaves can also be selectively "painted" with the solution using a brush or wiped on plants using a disposable cotton rag. Use rubber gloves approved for use with garden chemicals and avoid contact of the herbicide with skin and eyes.
A combination of 2,4-D and Banvel is also effective, but use 2,4-D with care as nearby plants may be sensitive to the drift. To kill the roots of large plants, cut the stem at soil level. Then paint the cut with undiluted 2,4-D. Mound soil over the treated stub. Amino triazole (Amitrol-T, Amino Triazole 90, and Weedazol) is also highly effective and safe to use. Available as a liquid or wettable powder, it should be applied during periods of rapid plant growth. Thorough coverage of the foliage is essential.
3.Use biological controls. Sheep and goats will eat poison ivy. Tether them in areas where you need poison ivy cleared. Not all municipalities or neighbors may welcome this control measure.
Integrated Pest Management Strategies
1. Pull small plants. If only a few small plants are found, pull and dispose of the plants using rubber gloves and arm protection. Avoid touching the leaves. Dispose of the plants in a plastic bag so they will not be touched by others. All parts of the plant are toxic. NEVER BURN THE PLANTS. The fumes are as toxic as touching the plant and worse if inhaled.
2. Use herbicides. For small areas, poison ivy killers available in aerosol cans may be a good choice. They are effective and convenient but are too expensive for treating large areas.
Another option is to use glyphosate (Roundup, Kleenup). Spray the leaves of actively growing plants taking care to protect nearby desirable plants from spray drift which can damage or kill them. Leaves can also be selectively "painted" with the solution using a brush or wiped on plants using a disposable cotton rag. Use rubber gloves approved for use with garden chemicals and avoid contact of the herbicide with skin and eyes.
A combination of 2,4-D and Banvel is also effective, but use 2,4-D with care as nearby plants may be sensitive to the drift. To kill the roots of large plants, cut the stem at soil level. Then paint the cut with undiluted 2,4-D. Mound soil over the treated stub. Amino triazole (Amitrol-T, Amino Triazole 90, and Weedazol) is also highly effective and safe to use. Available as a liquid or wettable powder, it should be applied during periods of rapid plant growth. Thorough coverage of the foliage is essential.
3.Use biological controls. Sheep and goats will eat poison ivy. Tether them in areas where you need poison ivy cleared. Not all municipalities or neighbors may welcome this control measure.
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文章
Dummer. ゛☀
2017年09月17日
Peach leaf curl is a springtime disease caused by the fungus, Taphrina deformans. It infects the leaves and shoots of peaches and nectarines. Apricots are immune. It is one of the most common diseases of these fruits. It causes the leaves to curl and turn reddish in color. A severe infection can cause reduced yields. 
Symptoms and Diagnosis
Symptoms first appear in spring. New leaves become curled and develop reddish areas. The reddish areas become thickened and puckered resulting in severely distorted leaves. As the disease progresses, the thickened areas turn yellowish gray and become covered with velvety spores. Affected leaves turn yellow or brown and fall prematurely. Affected shoots usually send out new leaves which often are unaffected by the disease unless rainy weather ensues. In more severe infections, shoots may become thickened and die.
Aphids can also cause leaves to curl. If present, the insects or cast skins will be evident to the naked eye.
Life Cycle
The fungus overwinters on bud scales, on twigs, and on fallen infected leaves. In spring the fungal spores are splashed onto newly developing leaves. During cool, wet weather the spores germinate on the young leaves and initiate infection. Development of the disease slows as temperatures increase. Older leaves are resistant to infection. Consequently, the disease is most prevalent in the spring.
Integrated Pest Management Strategies
1. Keep plant healthy — avoid excess fertilization. A healthy plant can better withstand the loss of leaves, but excess fertilization can cause succulent tissue that is very susceptible to infection.
2. Clean up diseased leaves. Raking up and disposing of diseased leaves can't hurt, but its value in controlling the disease is slight.
3. Don't panic.Once infection has occurred fungicidal sprays are not effective. A healthy plant should refoliate. Because refoliation normally occurs during warmer, dryer weather, re-infection is usually not a problem. Thinning the fruit crop in years of severe infection can also help maintain plant vigor. To limit damage the year after a moderate to severe infection, follow the protective spray program below.
4. Use properly timed protective fungicidal sprays. If leaf curl was a problem in the spring, apply a protective fungicidal spray after leaf fall in October or November or before bud break in late winter, January through February. After buds have begun to swell fungicidal sprays are not satisfactory. Do not apply to foliage. Chemicals effective in controlling leaf curl include copper-based fungicides like Bordeaux mixture, Bravo, lime-sulfur spray, or other brands that list the control of peach leaf curl on their label.
5. Replace the tree with a more disease tolerant variety. If you want to avoid using fungicidal sprays, consider replacing the tree with a more tolerant variety. ‘Redhaven’ and cultivars derived from ‘Redhaven’ have greater tolerance to peach leaf curl disease.
Symptoms and Diagnosis
Symptoms first appear in spring. New leaves become curled and develop reddish areas. The reddish areas become thickened and puckered resulting in severely distorted leaves. As the disease progresses, the thickened areas turn yellowish gray and become covered with velvety spores. Affected leaves turn yellow or brown and fall prematurely. Affected shoots usually send out new leaves which often are unaffected by the disease unless rainy weather ensues. In more severe infections, shoots may become thickened and die.
Aphids can also cause leaves to curl. If present, the insects or cast skins will be evident to the naked eye.
Life Cycle
The fungus overwinters on bud scales, on twigs, and on fallen infected leaves. In spring the fungal spores are splashed onto newly developing leaves. During cool, wet weather the spores germinate on the young leaves and initiate infection. Development of the disease slows as temperatures increase. Older leaves are resistant to infection. Consequently, the disease is most prevalent in the spring.
Integrated Pest Management Strategies
1. Keep plant healthy — avoid excess fertilization. A healthy plant can better withstand the loss of leaves, but excess fertilization can cause succulent tissue that is very susceptible to infection.
2. Clean up diseased leaves. Raking up and disposing of diseased leaves can't hurt, but its value in controlling the disease is slight.
3. Don't panic.Once infection has occurred fungicidal sprays are not effective. A healthy plant should refoliate. Because refoliation normally occurs during warmer, dryer weather, re-infection is usually not a problem. Thinning the fruit crop in years of severe infection can also help maintain plant vigor. To limit damage the year after a moderate to severe infection, follow the protective spray program below.
4. Use properly timed protective fungicidal sprays. If leaf curl was a problem in the spring, apply a protective fungicidal spray after leaf fall in October or November or before bud break in late winter, January through February. After buds have begun to swell fungicidal sprays are not satisfactory. Do not apply to foliage. Chemicals effective in controlling leaf curl include copper-based fungicides like Bordeaux mixture, Bravo, lime-sulfur spray, or other brands that list the control of peach leaf curl on their label.
5. Replace the tree with a more disease tolerant variety. If you want to avoid using fungicidal sprays, consider replacing the tree with a more tolerant variety. ‘Redhaven’ and cultivars derived from ‘Redhaven’ have greater tolerance to peach leaf curl disease.
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文章
Dummer. ゛☀
2017年09月17日
Black rot, caused by the fungus Guignardia bidwellii, is a serious disease of cultivated and wild grapes. The disease is most destructive in warm, wet seasons. It attacks all green parts of the vine – leaves, shoots, leaf and fruit stems, tendrils, and fruit. The most damaging effect is to the fruit. Note: Guignardia bidwellii forma parthenocissi causes a leaf spot on Boston ivy and Virginia creeper. Control is as for black rot of grapes.
Warm, muggy weather in the spring and summer, along with unsprayed fruit of susceptible varieties, may cause fruit to become almost completely rotted by harvest time. Black rot is not difficult to control if good cultural practices are followed along with the use of protective fungicide sprays.
Symptoms and Diagnosis
Leaves: Reddish brown and circular to angular spots appear on the upper surface of the leaves starting in late spring. As spots merge, they form irregular, reddish brown blotches. The number of spots or lesions per leaf varies from 2 to more than 100 depending on the severity of the disease. The center of the leaf spot turns tannish brown and is surrounded by a black margin. Black, speck-sized fruiting bodies (pycnidia) are arranged in a definite ring just inside the margin of the lesion. Only young, rapidly growing leaves are affected.
Fruit: Shortly after the flower petals fall, fruit infection can occur. Most infections start when the fruit is half to almost full size. A small spot will appear that becomes circular and whitish tan, often surrounded by a brown ring. This happens while the berry is still green. The spots grow rapidly and may cover half of the berry within 48 hours. Within a few days the entire berry becomes coal black, hard, and mummified. The surface of the withered fruit is soon covered with minute, black, pimple-like, sporeproducing pycnidia that are arranged in circular zones.
Life Cycle
The black rot fungus overwinters in canes, tendrils, and leaves on the grape vine and on the ground. Mummified berries on the ground or those that are still clinging to the vines become the major infection source the following spring. During rain, microscopic spores (ascospores) are shot out of numerous, black fruiting bodies (perithecia) and are carried by air currents to young, expanding leaves. In the presence of moisture, these spores germinate in 36 to 48 hours and eventually penetrate the leaves and fruit stems. The infection becomes visible after 8 to 25 days. When the weather is wet, spores can be released the entire spring and summer providing continuous infection. Cool weather slows growth of the fungus. It requires warm weather for optimal growth and a period of 2 to 3 days of rain, drizzle, or fog.
New black rot infections continue into late spring and summer during prolonged periods of warm, rainy weather. During August, the pycnidia are transformed into the overwintering stage (pycnosclerotia) that gives rise to perithecia within which the spring ascospores are produced, completing the disease cycle.
Integrated Pest Management Strategies
1. Planting. Space vines properly and choose a planting site where the vines will be exposed to full sun and good air circulation. Keep the vines off the ground and insure they are properly tied, limiting the amount of time the vines remain wet thus reducing infection.
2. Sanitation. Keep the fruit planting and surrounding areas free of weeds and tall grass. This practice will promote lower relative humidity and rapid drying of vines and thereby limit fungal infection.
3. Pruning. Prune the vines in early winter during dormancy. Select only a few strong, healthy canes from the previous year’s growth to produce the following season’s crop. Remove these prunings from the vineyard and burn or destroy.
4. Cultivation. Cultivate the vineyard before budbreak to bury the mummified berries. Diseased berries covered with soil do not produce spores that will reach the developing vines. For homegrown grapes, use 2–3 inches of leaf mulch or fine bark to cover infected debris.
5. Fungicides. Use protective fungicide sprays. Pesticides registered to protect the developing new growth include copper, captan, ferbam, mancozeb, maneb, triadimefon, and ziram. Important spraying times are as new shoots are 2 to 4 inches long, and again when they are 10 to 15 inches long, just before bloom, just after bloom, and when the fruit has set.
6. Cultivars. Cultivars with large, juicy berries are the most susceptible. In general, grapes that ripen late in the season are affected the least. Most commercial cultivars are sufficiently resistant if adequately protected with a fungicide spray program.
Warm, muggy weather in the spring and summer, along with unsprayed fruit of susceptible varieties, may cause fruit to become almost completely rotted by harvest time. Black rot is not difficult to control if good cultural practices are followed along with the use of protective fungicide sprays.
Symptoms and Diagnosis
Leaves: Reddish brown and circular to angular spots appear on the upper surface of the leaves starting in late spring. As spots merge, they form irregular, reddish brown blotches. The number of spots or lesions per leaf varies from 2 to more than 100 depending on the severity of the disease. The center of the leaf spot turns tannish brown and is surrounded by a black margin. Black, speck-sized fruiting bodies (pycnidia) are arranged in a definite ring just inside the margin of the lesion. Only young, rapidly growing leaves are affected.
Fruit: Shortly after the flower petals fall, fruit infection can occur. Most infections start when the fruit is half to almost full size. A small spot will appear that becomes circular and whitish tan, often surrounded by a brown ring. This happens while the berry is still green. The spots grow rapidly and may cover half of the berry within 48 hours. Within a few days the entire berry becomes coal black, hard, and mummified. The surface of the withered fruit is soon covered with minute, black, pimple-like, sporeproducing pycnidia that are arranged in circular zones.
Life Cycle
The black rot fungus overwinters in canes, tendrils, and leaves on the grape vine and on the ground. Mummified berries on the ground or those that are still clinging to the vines become the major infection source the following spring. During rain, microscopic spores (ascospores) are shot out of numerous, black fruiting bodies (perithecia) and are carried by air currents to young, expanding leaves. In the presence of moisture, these spores germinate in 36 to 48 hours and eventually penetrate the leaves and fruit stems. The infection becomes visible after 8 to 25 days. When the weather is wet, spores can be released the entire spring and summer providing continuous infection. Cool weather slows growth of the fungus. It requires warm weather for optimal growth and a period of 2 to 3 days of rain, drizzle, or fog.
New black rot infections continue into late spring and summer during prolonged periods of warm, rainy weather. During August, the pycnidia are transformed into the overwintering stage (pycnosclerotia) that gives rise to perithecia within which the spring ascospores are produced, completing the disease cycle.
Integrated Pest Management Strategies
1. Planting. Space vines properly and choose a planting site where the vines will be exposed to full sun and good air circulation. Keep the vines off the ground and insure they are properly tied, limiting the amount of time the vines remain wet thus reducing infection.
2. Sanitation. Keep the fruit planting and surrounding areas free of weeds and tall grass. This practice will promote lower relative humidity and rapid drying of vines and thereby limit fungal infection.
3. Pruning. Prune the vines in early winter during dormancy. Select only a few strong, healthy canes from the previous year’s growth to produce the following season’s crop. Remove these prunings from the vineyard and burn or destroy.
4. Cultivation. Cultivate the vineyard before budbreak to bury the mummified berries. Diseased berries covered with soil do not produce spores that will reach the developing vines. For homegrown grapes, use 2–3 inches of leaf mulch or fine bark to cover infected debris.
5. Fungicides. Use protective fungicide sprays. Pesticides registered to protect the developing new growth include copper, captan, ferbam, mancozeb, maneb, triadimefon, and ziram. Important spraying times are as new shoots are 2 to 4 inches long, and again when they are 10 to 15 inches long, just before bloom, just after bloom, and when the fruit has set.
6. Cultivars. Cultivars with large, juicy berries are the most susceptible. In general, grapes that ripen late in the season are affected the least. Most commercial cultivars are sufficiently resistant if adequately protected with a fungicide spray program.
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文章
Dummer. ゛☀
2017年09月16日
Leaf cutter bees (Megachile rotundata) are small native bees about ¼ inch long, robust and dark grey with a pollen brush on the underside of the abdomen. They are beneficial for the most part and only cause minor damage to ornamentals such as rose and ash by cutting half moon-shaped disks from the leaves. They are not aggressive but can give a mild sting if handled. They are important plant pollinators.
Symptoms and Diagnosis
The most characteristic symptom of leaf cutter bees are the half-moon shaped holes they make on the edges of leaves as they remove disks of leaf tissue to take back to form nest cells. A leaf may have a single disk removed or several.
Life cycle
Leafcutter bees are solitary bees. They do not form colonies. Females emerge in late spring, mate and form new nests in soft, rotten wood, the pith area of plants, or other existing holes of the correct size. They line the nest with the leaf fragments they collect, provision each cell with a mixture of nectar and pollen, lay an egg and seal the cell. Finished nests may contain a dozen cells or more. The young bees develop and remain in the cell overwintering as a full-grown larvae. There is only one generation a year.
Integrated Pest Management Strategies
1. Prevention. Eliminate breeding sites. Look for rotting boards with sawdust pushed out of excavated tunnels or thick stemmed plants with hollowed openings.
2. Mechanical control. Cover susceptible plants with cheesecloth or other loose netting during periods when leafcutter bees are most active (in late summer). To prevent leafcutter bees from tunneling into rose canes, seal exposed pith as canes are pruned. Place a thumb tack, bit of sealing wax or white glue on the opening.
3. Chemical controls. Insecticides are ineffective for preventing leaf cutting. Remember, leafcutter bees are native, beneficial bees, important as pollinators.
Symptoms and Diagnosis
The most characteristic symptom of leaf cutter bees are the half-moon shaped holes they make on the edges of leaves as they remove disks of leaf tissue to take back to form nest cells. A leaf may have a single disk removed or several.
Life cycle
Leafcutter bees are solitary bees. They do not form colonies. Females emerge in late spring, mate and form new nests in soft, rotten wood, the pith area of plants, or other existing holes of the correct size. They line the nest with the leaf fragments they collect, provision each cell with a mixture of nectar and pollen, lay an egg and seal the cell. Finished nests may contain a dozen cells or more. The young bees develop and remain in the cell overwintering as a full-grown larvae. There is only one generation a year.
Integrated Pest Management Strategies
1. Prevention. Eliminate breeding sites. Look for rotting boards with sawdust pushed out of excavated tunnels or thick stemmed plants with hollowed openings.
2. Mechanical control. Cover susceptible plants with cheesecloth or other loose netting during periods when leafcutter bees are most active (in late summer). To prevent leafcutter bees from tunneling into rose canes, seal exposed pith as canes are pruned. Place a thumb tack, bit of sealing wax or white glue on the opening.
3. Chemical controls. Insecticides are ineffective for preventing leaf cutting. Remember, leafcutter bees are native, beneficial bees, important as pollinators.
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文章
Dummer. ゛☀
2017年09月16日
Leaf blight, Volutella pachysandrae, on Japanese pachysandra can be very detrimental to the plant. Two other leaf spots, Phyllosticta and Gloeosporium, cause leaf spots on foliage but are not as destructive as Volutella.
Ground covers, such as pachysandra, are sometimes used where grass or other plants will not grow due to low light. Consequently, the environmental stress factors, including prolonged leaf wetness or dry soils, can favor certain infectious diseases in the sites.
Symptoms and Diagnosis
Volutella blight begins as small, brown to tan spots on the leaves that enlarge to form blotches. These blotches can then spread and coalesce to form a blight where young growing tissue, especially leaves and twigs, are killed. Concentric line patterns form within the brown spots as leaves yellow and fall. Infected stems become brown to black in color and die.
Circular, spreading areas on diseased plants will be noticeable in the planting. The disease will be especially severe when plants are crowded and wet conditions prevail.
Life Cycle
Many spore masses cause the spread of the disease, which is especially rapid among plants that have been weakened by the attack of scale insects or by winter injury. The sexual stage of this fungus is Pseudonectria pachysandricola. Under moist conditions, salmon- to pink-colored masses of fungal spores form on the surface of dead stems in spring. Initial infections may lead to large patches of plants killed.
Integrated Pest Management Strategies
1. Maintain plant vigor. Purchase healthy plants and maintain this condition by watering during drought. Water early in the day so that drying occurs before evening. Avoid splashing of water. Fertilize as needed or as indicated by soil testing.
2. Select planting area carefully. Plants should be planted in a well-draining soil. If the site is persistently wet, amend the soil or raise the bed before planting.
3. Removal. Lift out and destroy severely diseased plants. Bury or remove from the site. Do not place in the compost pile.
4. Use fungicides. It is difficult to thoroughly apply fungicides unless using a forceful sprayer. Fungicides can be applied beginning in spring and at 7 to 14 day intervals through early summer. Once temperatures rise above 90 degrees F, discontinue application. Pesticides registered for use include chlorothalonil (Daconil), copper, mancozeb, maneb, and thiophanate methyl (Cleary 3336).
5. Mulch. Mulch with leaf mold in the spring to cover up fallen debris containing inoculum.
6. Thinning. Thin plants in fall, during dry weather, to remove dense growth.
7. Pests. Scale is a harmful pest on pachysandra and may make it more susceptible to disease. The female insects are dark brown and shaped like oyster shells. The males are smaller and narrower, pure white, and are very prominent on the leaves and stems. Heavy infestations of scale can be brought under control by applying summer oil spray before the new growth starts in spring. Follow this with several applications of a scale insecticide like malathion or Sevin at 2-week intervals or several applications of a scale insecticide or summer oil every 10 days to 2 weeks starting in mid-May.
Ground covers, such as pachysandra, are sometimes used where grass or other plants will not grow due to low light. Consequently, the environmental stress factors, including prolonged leaf wetness or dry soils, can favor certain infectious diseases in the sites.
Symptoms and Diagnosis
Volutella blight begins as small, brown to tan spots on the leaves that enlarge to form blotches. These blotches can then spread and coalesce to form a blight where young growing tissue, especially leaves and twigs, are killed. Concentric line patterns form within the brown spots as leaves yellow and fall. Infected stems become brown to black in color and die.
Circular, spreading areas on diseased plants will be noticeable in the planting. The disease will be especially severe when plants are crowded and wet conditions prevail.
Life Cycle
Many spore masses cause the spread of the disease, which is especially rapid among plants that have been weakened by the attack of scale insects or by winter injury. The sexual stage of this fungus is Pseudonectria pachysandricola. Under moist conditions, salmon- to pink-colored masses of fungal spores form on the surface of dead stems in spring. Initial infections may lead to large patches of plants killed.
Integrated Pest Management Strategies
1. Maintain plant vigor. Purchase healthy plants and maintain this condition by watering during drought. Water early in the day so that drying occurs before evening. Avoid splashing of water. Fertilize as needed or as indicated by soil testing.
2. Select planting area carefully. Plants should be planted in a well-draining soil. If the site is persistently wet, amend the soil or raise the bed before planting.
3. Removal. Lift out and destroy severely diseased plants. Bury or remove from the site. Do not place in the compost pile.
4. Use fungicides. It is difficult to thoroughly apply fungicides unless using a forceful sprayer. Fungicides can be applied beginning in spring and at 7 to 14 day intervals through early summer. Once temperatures rise above 90 degrees F, discontinue application. Pesticides registered for use include chlorothalonil (Daconil), copper, mancozeb, maneb, and thiophanate methyl (Cleary 3336).
5. Mulch. Mulch with leaf mold in the spring to cover up fallen debris containing inoculum.
6. Thinning. Thin plants in fall, during dry weather, to remove dense growth.
7. Pests. Scale is a harmful pest on pachysandra and may make it more susceptible to disease. The female insects are dark brown and shaped like oyster shells. The males are smaller and narrower, pure white, and are very prominent on the leaves and stems. Heavy infestations of scale can be brought under control by applying summer oil spray before the new growth starts in spring. Follow this with several applications of a scale insecticide like malathion or Sevin at 2-week intervals or several applications of a scale insecticide or summer oil every 10 days to 2 weeks starting in mid-May.
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文章
Dummer. ゛☀
2017年09月16日
Leaf scorch may occur on any species of tree or shrub as well as herbaceous plants. It is a widespread noninfectious disease or disorder. Scorch most often occurs following prolonged periods of dry, windy weather or bright sunshine when the roots are unable to supply water to the foliage as rapidly as it is lost by transpiration from the leaves. Unfavorable locations, such as sandy or gravelly soil, near obstructions or pavement that restrict root growth, or exposed windy slopes usually promote scorch. Anything that affects the plant’s ability to take up water, including insect and disease problems, can result in leaf scorch. Herbicides and pesticides may also contribute to scorch. Do not spray on windy days to eliminate drift problems and do not allow mist to settle onto trees.
In mild cases of leaf scorch, the leaves remain attached, and little damage results. In more severe cases, plants may drop many of their leaves prematurely, although such plants do not die. Where leaf scorch occurs each year, such annual stress will gradually weaken the plant, making it more susceptible to insects and diseases.
Symptoms and Diagnosis
Browning of leaf margins and/or yellowing or darkening of the areas between the main leaf veins are symptoms of leaf scorch. Due to environmental causes, leaves may dry, turn brown, and become brittle. Look for damage to trees and shrubs on the upper portion on the sunny, southern side and on the windy side. Premature dropping of leaves and twig dieback may occur during the late summer. Symptoms usually appear after drying winds in conjunction with periods of hot, dry weather.
Leaf scorch on narrow leaf evergreens appears as brown or purple brown discoloration of the needle tips. If unfavorable conditions become more severe, browning of needles increases. This should not be confused with the browning and shedding of older interior needles. Scorch may result from hot, dry weather in summer or from strong, dry winter winds when the ground is frozen. Symptoms may not become apparent for a month or more after the initial injury.
Winter leaf scorch in evergreen plants usually appears as two long, brown areas paralleling the main leaf vein.
Life Cycle
Although plants can experience scorch with no insects or disease pathogens involved, insect and disease damage can also affect the plant’s uptake of water. In some cases, insect damage such as leafhopper (hopper burn) or specific scorch diseases caused by fungi or bacteria can produce similar symptoms. Scorch can also reduce the health of a plant making it more susceptible to attack by insects and diseases.
Integrated Pest Management Strategies
1.Water when needed and maintain plant vigor. Plant in a fertile, well-drained soil at the same depth the plants grew in at the nursery and with an adequate supply of organic matter. Soil should be moist to a depth of 10 to 12 inches after a thorough watering. This should be done about once weekly. It is very important for the trees, especially broadleaf and needled evergreens, to be well watered going into the winter period. Water during this period if seasonal rains are not adequate or during the winter when the soil is not frozen. Annuals and perennials require more frequent watering than most trees and shrubs.
2. Fertilize. Fertilize plants in early spring based on a soil test and the directions printed on the fertilizer container. Nitrogen should be applied annually based on the area to be fertilized, the type of plant, and the diameter of the trunk. Do not fertilize with nitrogen in the late fall as it may cause new soft growth easily damaged by cold weather.
3. Mulch. Organic mulches (pine needles, wood chips, composted leaves, pine bark, cypress mulch) can help retain moisture during the summer and fall droughts. In the winter this mulch prevents the alternate freezing and thawing of the soil. Mulch will also cool the soil in summer.
4. Screens. Screens may be used to protect trees and plants in areas exposed to wind and sun, but it is best not to plant tender plants in these exposures.
5. Exposure. Other factors which can result in scorch are excessive fertilizer, deicing salt, herbicide, dog urine, trash fires, leaking sewer or gas mains, girdling roots or strangling wires, vehicle exhaust, and heat reflected from buildings. Elimination of the exposure to these elements is the only correction.
6. Physical hazards. Avoid root injury when digging near trees and shrubs. Care should be taken to not injure the bark and roots when using lawnmowers, weed whips, and edging tools.
In mild cases of leaf scorch, the leaves remain attached, and little damage results. In more severe cases, plants may drop many of their leaves prematurely, although such plants do not die. Where leaf scorch occurs each year, such annual stress will gradually weaken the plant, making it more susceptible to insects and diseases.
Symptoms and Diagnosis
Browning of leaf margins and/or yellowing or darkening of the areas between the main leaf veins are symptoms of leaf scorch. Due to environmental causes, leaves may dry, turn brown, and become brittle. Look for damage to trees and shrubs on the upper portion on the sunny, southern side and on the windy side. Premature dropping of leaves and twig dieback may occur during the late summer. Symptoms usually appear after drying winds in conjunction with periods of hot, dry weather.
Leaf scorch on narrow leaf evergreens appears as brown or purple brown discoloration of the needle tips. If unfavorable conditions become more severe, browning of needles increases. This should not be confused with the browning and shedding of older interior needles. Scorch may result from hot, dry weather in summer or from strong, dry winter winds when the ground is frozen. Symptoms may not become apparent for a month or more after the initial injury.
Winter leaf scorch in evergreen plants usually appears as two long, brown areas paralleling the main leaf vein.
Life Cycle
Although plants can experience scorch with no insects or disease pathogens involved, insect and disease damage can also affect the plant’s uptake of water. In some cases, insect damage such as leafhopper (hopper burn) or specific scorch diseases caused by fungi or bacteria can produce similar symptoms. Scorch can also reduce the health of a plant making it more susceptible to attack by insects and diseases.
Integrated Pest Management Strategies
1.Water when needed and maintain plant vigor. Plant in a fertile, well-drained soil at the same depth the plants grew in at the nursery and with an adequate supply of organic matter. Soil should be moist to a depth of 10 to 12 inches after a thorough watering. This should be done about once weekly. It is very important for the trees, especially broadleaf and needled evergreens, to be well watered going into the winter period. Water during this period if seasonal rains are not adequate or during the winter when the soil is not frozen. Annuals and perennials require more frequent watering than most trees and shrubs.
2. Fertilize. Fertilize plants in early spring based on a soil test and the directions printed on the fertilizer container. Nitrogen should be applied annually based on the area to be fertilized, the type of plant, and the diameter of the trunk. Do not fertilize with nitrogen in the late fall as it may cause new soft growth easily damaged by cold weather.
3. Mulch. Organic mulches (pine needles, wood chips, composted leaves, pine bark, cypress mulch) can help retain moisture during the summer and fall droughts. In the winter this mulch prevents the alternate freezing and thawing of the soil. Mulch will also cool the soil in summer.
4. Screens. Screens may be used to protect trees and plants in areas exposed to wind and sun, but it is best not to plant tender plants in these exposures.
5. Exposure. Other factors which can result in scorch are excessive fertilizer, deicing salt, herbicide, dog urine, trash fires, leaking sewer or gas mains, girdling roots or strangling wires, vehicle exhaust, and heat reflected from buildings. Elimination of the exposure to these elements is the only correction.
6. Physical hazards. Avoid root injury when digging near trees and shrubs. Care should be taken to not injure the bark and roots when using lawnmowers, weed whips, and edging tools.
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文章
Dummer. ゛☀
2017年09月16日
Angular leaf spot is a common bacterial disease of Goldsturm coneflower (Rudbeckia fulgida var. sullivantii 'Goldsturm')
Two common leaf spots affect rudbeckia in the St. Louis area. Both rarely endanger the survival of the plant but both can cause depreciation of the foliage. One is caused by a fungus and the other by a bacterium.
Symptoms and Diagnosis
Septoria leaf spot is caused by the fungus Septoria rudbeckiae and causes small 1/8 - 1/4 inch spots on the leaves. Small, black, pinpoint size fruiting bodies (pycnidia) form in the center of the spots. Lower leaves are affected first. The disease then moves up the plant by splashing water. Angular leaf spot of rudbeckia is most common on the cultivar 'Goldsturm'. It begins as small, brown, angular spots on lower leaves, which may appear water-soaked but can quickly expand to affect the whole leaf. It begins at the base of the plant and moves up. Angular leaf spot is caused by a bacterium. The absence of fungal pycnidia and the presence of bacterial streaming under microscopic examination can be used to differentiate angular leaf spot from septoria leaf spot.
Life Cycle
Both organisms overwinter in infected debris in the garden. Initial infection occurs in late spring or early summer on the lower leaves and then spread up the plant. Plants are rarely killed, but plants can look unsightly by early fall.
Integrated Pest Management Strategies
1. Clean up old foliage each fall and then live with the disease. Sanitation can go a long way to helping control both diseases. Collect and dispose of old foliage in the fall or by late winter to help prevent early infection.
2. Provide good air circulation and avoid overhead watering. Keeping the leaves dry and help prevent movement of the fungi or bacteria by not watering overhead. If irrigation is necessary, use soaker hoses or at least water early in the day so the foliage can dry before nightfall.
3. Apply chemical protectants. Septoria leaf spot can be controlled with fungicides containing chlorothalonil or copper. Angular leaf spot can be controlled by applying a copper-based fungicide such as Bordeaux mixture as needed started in early spring. Kocide is also effective. Apply at the first signs of disease to protect healthy yet unaffected foliage.
Two common leaf spots affect rudbeckia in the St. Louis area. Both rarely endanger the survival of the plant but both can cause depreciation of the foliage. One is caused by a fungus and the other by a bacterium.
Symptoms and Diagnosis
Septoria leaf spot is caused by the fungus Septoria rudbeckiae and causes small 1/8 - 1/4 inch spots on the leaves. Small, black, pinpoint size fruiting bodies (pycnidia) form in the center of the spots. Lower leaves are affected first. The disease then moves up the plant by splashing water. Angular leaf spot of rudbeckia is most common on the cultivar 'Goldsturm'. It begins as small, brown, angular spots on lower leaves, which may appear water-soaked but can quickly expand to affect the whole leaf. It begins at the base of the plant and moves up. Angular leaf spot is caused by a bacterium. The absence of fungal pycnidia and the presence of bacterial streaming under microscopic examination can be used to differentiate angular leaf spot from septoria leaf spot.
Life Cycle
Both organisms overwinter in infected debris in the garden. Initial infection occurs in late spring or early summer on the lower leaves and then spread up the plant. Plants are rarely killed, but plants can look unsightly by early fall.
Integrated Pest Management Strategies
1. Clean up old foliage each fall and then live with the disease. Sanitation can go a long way to helping control both diseases. Collect and dispose of old foliage in the fall or by late winter to help prevent early infection.
2. Provide good air circulation and avoid overhead watering. Keeping the leaves dry and help prevent movement of the fungi or bacteria by not watering overhead. If irrigation is necessary, use soaker hoses or at least water early in the day so the foliage can dry before nightfall.
3. Apply chemical protectants. Septoria leaf spot can be controlled with fungicides containing chlorothalonil or copper. Angular leaf spot can be controlled by applying a copper-based fungicide such as Bordeaux mixture as needed started in early spring. Kocide is also effective. Apply at the first signs of disease to protect healthy yet unaffected foliage.
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