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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
Cucumber beetles feed on all cucurbits from seedling emergence to harvest. Feeding by the adults causes scarring on stems and fruit of cucurbits. However, the most important damage by the insect is the transmission of bacterial wilt, which is lethal to the vine. Adult beetles also may feed on a number of different plants, including blossoms of rose and zinnia. Cucumber beetles are about 1/3 inch long. They have a black head and their wing covers are either green with 12 black spots or alternating black and yellow stripes. They fly readily when disturbed.
Symptoms and Diagnosis Adult beetles damage cucurbits in several ways. They may feed on young seedlings or transplants, completely consuming stems and cotyledons, and killing or stunting the young plants. The adult also damages more mature vines and fruit by chewing holes in leaves and rinds. The worst damage by the beetle is the transmission of bacterial wilt when the plants are young. The infected vines will gradually wilt and die.
Life Cycle Adult beetles overwinter in woodlands, fence rows, under fallen leaves, under bark, and on weeds. In early summer when temperatures near 70 degrees F, the beetles become active and feed on young plants. After mating, eggs are laid in the soil near plant bases. Emerging larvae feed on plant roots for 3–6 weeks. Emerging adults appear during midsummer and feed on above ground plant parts of host plants. There are 2–3 generations a year.
Integrated Pest Management Strategies 1. Use row covers on young plants to exclude the beetles. Use floating row covers, screens, or cheesecloth to protect seedlings. Keep the covers in place until the plants begin to bloom. 2. Plant a trap crop of squash or pumpkin to attract beetles away from cucumber plants. Time the planting of the trap crop to emerge one week before the main cucurbit crop. The presence of cucumber beetles on the trap crop can help you time control practices. Trap crops can be pulled from the garden and the insects and eggs on the crop can be destroyed.
3. Plant tolerant varieties. Varieties of cucumbers tolerant to bacterial wilt are available. A couple of these are ‘County Fair ‘83’ or ‘Saladin’. Some varieties are less appealing as food for cucumber beetles. These include ‘Ashley’, ‘Chipper’, and ‘Gemini’ cucumber. ‘Heart of Gold’ muskmelon and ‘Crimson Sweet’ watermelon also resist attack from beetles. 4. Delay planting time. Planting time can influence beetle feeding damage and wilt transmission. By planting early to mid-June, some beetle feeding can be eliminated. However, this eliminates early harvest and may be too late for some varieties.
5. Insecticidal sprays may be needed if populations of cucumber beetles are high. Treat early in the season before over wintering beetles have a chance to lay eggs. Pesticides registered for use include carbaryl (Sevin), endosulfan (Thiodan), permethrin and pyrethrins.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
The bean leaf beetle, Ceratoma trifucata, is one of the most serious pests of commercial soybeans. It is an occasional pest of snap beans, soybeans and other similar crops in the home vegetable garden.
Symptoms and Diagnosis Adult bean leaf beetles prefer tender young plant tissue and they can cause significant damage by defoliating and killing young plants. Older plants will be less vigorous and have decreased yields. Feeding damage to leaves appears as approximately 1/8 inch diameter round holes between major veins. (Grasshoppers or caterpillars cause larger irregular holes or jagged leaf margins; flea beetles cause smaller holes.) There may also be chewing damage on the pods. While this damage may cause complete pod loss or spread disease in commercial soybeans, it is generally just cosmetic in home gardens. Although the damage caused by the larvae is less severe, they feed on bean roots, especially the root nodules, decreasing the plant’s ability to fix nitrogen.
Life Cycle Bean leaf beetle adults are about ¼ inch long and are commonly greenish yellow to tan with 4 black spots. However, they may also be red, orange, or gray with spots, stripes, both or none. They are distinguished from other beetles by the presence of a black triangle at the top of their wing covers. The beetles overwinter as adults in leaf litter and become active in spring when the temperatures reach 50 to 55 degrees F. The females lay 130 to 200 reddish oval eggs in the upper 5 inches of the soil at the base of plant stems. The larvae, which are white with a black head, emerge in 5-7 days and feed on underground plant parts for 3 to 6 weeks. After a pupal stage of about one week, the adults emerge and begin to eat, mate and lay eggs. In Missouri, a second generation matures in September and these adults will move to overwintering sites in October.
Integrated Pest Management Strategies 1. Practice good garden sanitation by removing leaf litter and controlling weeds, especially those in the legume family. 2. Plant beans later in spring to avoid adults as they emerge from their overwintering sites.
3. Handpick adults and drop them into a container of soapy water if the bean leaf beetle population is small. Since the beetles tend to tumble off the leaves when disturbed, it may help to hold the container under the plants. 4. Spray with an insecticide. Pesticides such as permethrin is an option. Be sure to use an insecticide that is registered for bean leaf beetles on your crop and follow the directions carefully.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
Several viruses infect tomatoes and peppers. The two most common are tobacco mosaic virus and cucumber mosaic virus.
Symptoms and Diagnosis Symptoms vary depending upon the virus and strain, the plant, time of year, and environmental conditions. The most common symptoms include leaf mottling; puckering or curling; stem and petiole streaking; rough, deformed or spotted fruit; stunted plants; and blossom and fruit drop. Some viruses cause the leaves of tomatoes to become fernlike or develop a thin "shoestring" appearance. Symptoms may be confused with herbicide damage.
Life Cycle Viruses have no active way of penetrating plant parts. They rely upon mechanical wounds, infected seeds, and being carried in the bodies of insects for transmission. The virus can also be present in tobacco and transmitted to plants by the hands of people who smoke. Once inside the plant cells, the virus replicates. The virus does not usually kill the plant and takes over the metabolic processes of the leaf, resulting in abnormal cell functioning and growth.
Integrated Pest Management Strategies 1. Remove diseased plants. Once a plant is infected, there are no practical field methods of curing the plant of the virus. Remove infected plants as soon as they are noticed to reduce the chance of spreading the disease. 2. Follow strict sanitation. Persons handling plants must refrain from the use of tobacco or risk infecting the plants. Remove weeds in the area that could harbor the virus.
3. Control insects. Because insects, especially aphids, vector cucumber mosaic, make every effort to keep insects under control using sticky traps or insecticides. 4. Plant resistant varieties. In subsequent years, plant varieties that are resistant to the most common viruses. Look for varieties that are marked TMV or CMV after the variety name.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
Viral infections can reduce plant vigor by disrupting cellular functioning, but do not commonly kill plants. Tobacco mosaic is one of the most highly persistent tomato diseases because it can remain viable without a host for many years and it is able to withstand high heat. The virus is spread primarily by mechanical methods. Gardeners can contaminate their hands when they touch tobacco products or infected plants and weeds and spread the virus to healthy plants.
Symptoms and Diagnosis Tobacco mosaic virus is not as distinct as other viruses, but yellow-green mottling on leaves is the most characteristic symptom of the disease. Infected plants have stunted growth, and flowers and leaflets may be curled, distorted, and smaller than normal in size. Open blooms may have brown streaks through them. Yellow, chlorotic spotting is characteristic of pepper plants that are infected.
Life Cycle Tobacco mosaic virus survives on infected seeds, plant debris, and even clothing for months or years. The virus enters plants through wounds sustained in transplanting or pruning. It spreads rapidly once it is in the host. The virus can remain viable for years on dried plant debris and is extremely tolerant of very high temperatures. Tobacco products are the most common source of inoculum; smokers can infect plants by handling them. The virus is not spread by aphids.
Integrated Pest Management Strategies 1. Remove and destroy infected plants. Pull plants with mosaic symptoms immediately. Remove the debris from the garden area and bury them if possible. 2. Keep your garden weed-free. Some weed may be harboring the virus. These represent sources of inoculum.
3. Always wash your hands thoroughly and disinfect tools. Before handling plants, wash with soap and water, especially if you're a smoker. 4. Plant resistant varieties of tomato. Suggested varieties include: ‘Big Pick’, ‘Celebrity’, ‘President’, and ‘Park's Extra Early Hybrid’. Other resistant varieties will be labeled TMV resistant.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
Septoria leaf spot is caused by a fungus, Septoria lycopersici. It is one of the most destructive diseases of tomato foliage and is particularly severe in areas where wet, humid weather persists for extended periods.
Symptoms and Diagnosis Septoria leaf spot usually appears on the lower leaves after the first fruit sets. Spots are circular, about 1/16 to 1/4 inch in diameter with dark brown margins and tan to gray centers with small black fruiting structures. Characteristically, there are many spots per leaf. This disease spreads upwards from oldest to youngest growth. If leaf lesions are numerous, the leaves turn slightly yellow, then brown, and then wither. Fruit infection is rare.
Life Cycle The fungus overwinters on infected tomato debris or on weeds in the nightshade family, the same family to which tomatoes belong. The fungus can also survive on equipment such as plant stakes and cages. Long periods of high relative humidity, temperatures of 60–80 degrees F, and leaf wetness are ideal conditions for development and spread of the pathogen. Integrated Pest Management Strategies 1. Remove diseased leaves. If caught early, the lower infected leaves can be removed and burned or destroyed. However, removing leaves above where fruit has formed will weaken the plant and expose fruit to sunscald. At the end of the season, collect all foliage from infected plants and dispose of or bury. Do not compost diseased plants.
2. Improve air circulation around the plants. If the plants can still be handled without breaking them, stake or cage the plants to raise them off the ground and promote faster drying of the foliage. 3. Mulch around the base of the plants. Mulching will reduce splashing soil, which may contain fungal spores associated with debris. Apply mulch after the soil has warmed. 4. Do not use overhead watering. Overhead watering facilitates infection and spreads the disease. Use a soaker hose at the base of the plant to keep the foliage dry. Water early in the day.
5. Control weeds. Nightshade and horsenettle are frequently hosts of Septoria leaf spot and should be eradicated around the garden site. 6. Use crop rotation. Next year do not plant tomatoes back in the same location where diseased tomatoes grew. Wait 1–2 years before replanting tomatoes in these areas.
7. Use fungicidal sprays. If the above measures do not control the disease, you may want to use fungicidal sprays. Fungicides will not cure infected leaves, but they will protect new leaves from becoming infected. Apply at 7 to 10 day intervals throughout the season. Apply chlorothalonil, maneb, macozeb, or a copper-based fungicide, such as Bordeaux mixture, copper hydroxide, copper sulfate, or copper oxychloride sulfate. Follow harvest restrictions listed on the pesticide label.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
Root-knot nematodes are microscopic, plant-parasitic roundworms in the genus, Meloidogyne. Normally they exist in sandy soil in hot climates or short winters, but they have spread to our region as well. In Missouri alone 40 species of parasitic nematodes exist. About 2000 plants are susceptible to infection by these nematodes, and they can cause global crop loss. Root-knot nematode larvae infect plant roots that drain the plant’s ability to take up water and sufficient nutrients. Because of their microscopic size the nematodes go unnoticed until serious symptoms appear. The pathogenic nematodes can allow entrances for root rots, and wilts. They can also transmit viral diseases.
Symptoms and Diagnosis A plant infected with root-knot nematodes often exhibits the same signs of nutrient deficiency. It may be stunted, yellowed, or wilted, and can lead to premature death of the plant. Below the ground, the roots of the plant are swollen or knotted with root galls, and unless a plant is removed from the soil to examine the roots, the cause of the poor plant growth remains undetected. The appearance of the galls on the roots can be confused with nitrogen-fixing nodules common in the legume family. However it is easy to distinguish between them, as the nitrogen nodules can be easily rubbed off while the nematode galls cannot be removed.
Life Cycle The root-knot nematode is parthenogenic, that is a single female can reproduce without males and a new generation can occur every 28 days if conditions are ideal. Inside the gall, the enlarged female appears as a shiny white body, the size of a pinhead. She deposits 300 to 500 eggs in a protective jelly-like material. These glistening white to yellow egg masses are present on the root surfaces. Juveniles emerge from the eggs in the soil and penetrate between and through cells at the center of the root, usually near the growing tip. These larvae actively feed and remain at this same site. The juvenile stage can over-winter even under very unfavorable conditions. New adult nematodes develop from the larvae and start the cycle again.
Integrated Pest Management Strategies 1. Never buy or plant any stunted-yellowed plants. When a new plant’s roots are examined and its roots contain root knots that will not easily rub off, do not plant it. If someone gives you a division of their plant whose roots contain these root-knots, never add it to your garden because it will contaminate all of your healthy plants with the nematodes. 2. Keep plants healthy and avoid stressing plants and water plants during periods of high temperatures and drought. Also keep other insect pests and fungal diseases under control. Control weeds as they can act as hosts to these nematodes. Keep tools clean.
3. ;Rotate crops, planting nematode resistant plants when possible. It may take 3-5 years to kill off these nematodes before replanting the same plant. 4. Destroy any plants you discover that are infested with root-knot nematodes and don’t compost them. Replace all the soil before adding a new plant to this area.
5. Soil solarization has demonstrated some success in eliminating root-knot nematodes. Thoroughly moisten the soil and cover with clear plastic in full sun during the hottest months of the year. The soil must maintain these high temperatures for a period of at least 4-6 weeks to be effective. Re-moisten the soil under the plastic if it dries out. 6. No chemical controls are advised for home gardeners. Some restricted use chemicals are available for commercial, licensed applicators.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
A strain of the fungus, Phytophthora infestans, causes late blight in tomatoes. As the common name implies, Phytophthora is prevalent on tomato hosts in late summer, after the plants have bloomed. Late blight is more common in north central and northeastern states, but is observed in the Midwest when the humidity is high and temperatures are around 68 degrees F late in the growing season. Watch for the disease when cool, moist nights are followed by warm, humid days.
Symptoms and Diagnosis One of the first symptoms of late blight is watersoaked patches on older leaves. Late blight attacks the older leaves first, then spreads to the fruit. Green-black watery patches develop on the upper surfaces of older leaves. These patches will enlarge quickly, and in moist weather, a downy growth may develop on the underside of the leaf. On the fruit, you will see rough, firm, dark-colored spots.
Life Cycle The fungus overwinters on tomato and potato plant debris, including potato tubers. The fungus can produce spores over a broad range of temperatures although spores are most infective at temperatures of 68 degrees F with high humidity. The spores are transmitted by water or are wind blown and may be introduced from diseased plants in nearby gardens. The fungus invades the plant through leaf stomata. Infection rarely occurs when temperatures are higher than 80 degrees F and humidity is less than 90%.
Integrated Pest Management Strategies 1. Plant resistant varieties. Several tomato varieties are designated as resistant to late blight. 2. Avoid overhead watering. Avoid working around plants when they are wet. Both of these practices can spread the fungal spores from plant to plant. 3. Clean up all garden debris in the fall. Remove and destroy any affected plants as soon as they are observed.
4. Practice crop rotation. Do not plant tomatoes, potatoes, and celery in succession. All of these crops are susceptible. 5. Use a copper-based fungicide. Apply when symptoms are first identified. Reapply at 7–10 day intervals.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
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.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
Early blight is a fungal disease, Alternaria sp., that occurs on tomatoes throughout North America. Early blight can affect seedlings but is generally observed on older plants and is especially severe on plants of poor vigor. Plants infected with the fungus can display collar rust on the stems, infected older leaves, and fruits that crack at the stem. Infection on leaves is the most common symptom.
Symptoms and Diagnosis The appearance of circular or irregular dark spots on the lower, more mature leaves is one of the first symptoms of infection. Eventually, the spots enlarge into a series of concentric rings surrounded by a yellow area. The entire leaf may be killed and will drop off the plant. Early blight can result in extensive defoliation, exposing fruit to sunscald and reducing yields. This disease typically progresses from the base of the plant, upward.
Life Cycle Early blight spores survive on old plant debris or in the soil. Spores are spread by wind and rain, but occasionally, flea beetles transmit this disease. Fungal spores enter a host through wounds in the plant cuticle. Spores thrive in moist, warm temperatures (80–90 degrees F) and can persist in partially decomposed garden waste for at least a year. Integrated Pest Management Strategies 1. Plant resistant varieties. Varieties such as ‘Early Cascade’, ‘Floramerica’, ‘Jetstar’, ‘Manlucie’, ‘Supersonic’, and ‘Surecrop’ have some tolerance to early blight. These varieties will require a less intensive management program than susceptible varieties.
2. Maintain plant vigor. Stressed plants are more susceptible to early blight. Water the plants regularly, but don't fertilize until the plants are well-established and in full blossom. Do not mulch until the soil is warm. 3. Do a thorough cleanup of the garden in the fall. Remove plant debris or till it into the soil. Pull weeds that compete for light, water, and nutrients, especially nightshade, horse nettle, and other weeds in the tomato family. 4. Rotate crops. Practice a 2- or 3-year crop rotation. Avoid planting eggplant or potatoes where tomatoes were last planted.
5. Avoid activity when plants are wet. Confine staking and picking to times when foliage is dry. Disease is more readily spread when plant foliage is wet. 6. Protect clean foliage with a fungicide. Effective fungicides include copper (Kocide), chlorothalonil (Bravo, Daconil), mancozeb, or maneb. Apply at fruit set and reapply every 7–14 days.
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Dummer. ゛☀
2017年09月19日
Dummer. ゛☀
Clubroot is a fungal disease that affects a number of plants in the cabbage family including cabbages, radish, mustard and ornamentals such as candytuft. It is caused by the fungus Plasmodiophora brassicae and gets its name from the club-like roots it induces in infected plants. Its diagnosis is often missed as the infected plant part, the roots, are underground and out of sight.
Symptoms and Diagnosis The first symptom is usually wilting during average daily conditions but recovery at night. The older leaves may yellow and die and the plants look stunted. Examination of the root system reveals enlarged roots that make them look club-like and reduced feeder roots. The reduction in feeder roots as well as disruption of the water conducting tissue in the roots causes the drought-like symptoms. Development of the disease if favored by a low soil pH (below 7.0), cool soil, and excess soil moisture. The organism can survive in the soil for over 10 years. Since most soils in the St. Louis area are above a pH of 7 the disease is rare in our area.
Life Cycle Clubroot is a soil-borne fungus that infects plants through root hairs by zoospores. After infection the roots enlarge and many spores are produced in the swollen roots. The mobile zoospores can re-infect other roots on the plant or nearby plants. Late in the season resting spores are produced. When roots die and decay the resting spores are released into the soil where they can survive for many years and be transported through the soil by water movement and garden equipment.
Integrated Pest Management Strategies 1. Remove diseased plants. The disease organism can reside in the soil for many years so although quick removal of diseased plants is recommended the disease may return if plants in the cabbage family are planted in the infested soil the following year. Also remove any cabbage family weeds such as wild mustard, which can harbor the disease.
2. Add lime. Since problems are more severe in acid soils (pH 5.0-7.0) adding lime to acid soils can help control the disease. 3. Rotate crops Rotate where you grow cabbage, radishes, mustards, etc in your garden. Wait 5-6 years before replanting in an area.
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