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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Dodder is an annual seed-bearing parasitic vine in the dodder family (formerly placed in the morning-glory family). Its thin, thread-like, yellow or orange stems grow rapidly entwining and covering their host plants. Cuscate is the most common genus and is found throughout the US and Canada. Of the 50 species that occur, most are found in tropical and warm-temperate areas but some species also occur in cooler areas including St. Louis where they can grow from seed each year and infest herbaceous and small woody plants. Since seeds can be difficult to separate from some agricultural crops dodder has been spread widely through agriculture.
Life Cycle Dodder seeds germinate in soil and can live on their own for 5 to 10 days until they are about a foot tall. If they have not found a suitable host by this time the seedlings will die. Seedlings that find a suitable host twine around the plant and insert haustoria (modified adventitious roots) into the tender stem. The haustoria penetrate and tap the plant's vascular system for water, minerals and nutrients. Plants are weakly photosynthetic, but most produce very little food on their own. They rely upon their host plant for survival. As the vine taps the host plant its connection to the soil is severed. Small, white, bell-shaped flowers form in late summer and early fall and can produce copious amounts of seed. Plants are annual and are killed by frost. Plants regrow from seed each year.
Integrated Pest Management Strategies 1. Remove the plants. As soon as the thin vining stems of dodder are observed they should be gathered and removed before seed is set. Removal of the host plant is usually recommended. Complete eradication from the host plant is usually not possible. 2. Scout for and remove new seedlings as they appear. Monitor areas previously infested with dodder closely and pull young seedling before they attach themselves to new plants and certainly before they set seed. Seeds can survive in the soil for more than 20 years. 3. Treat with an herbicide. Dodder and the host plant can be killed by treating with glyphosate, a non-selective herbicide. As a follow-up measure to kill germinating seeds, treat soil with a preemergent herbicide such as Dacthal before seeds germinate in spring.
Organic Strategies Strategies 1 and 2 are strictly organic approaches.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Mosses are small, primitive plants that have reduced leaves and a mass of fine, thread-like stems. A mild, wet winter combined with turfgrass which is thin and weak offers an opportunity for moss and/or algae growth. Mosses are not parasitic on turfgrass. They produce their own food, grow where grass will not, and form a soft mat of growth, which makes a barrier, preventing grass from growing. Shady conditions and infertile and/or compacted, poorly drained soil encourage moss growth.
Symptoms and Diagnosis Moss in the lawn is quite visible and can be annoying. Large areas void of grass may be covered by moss. These small primitive plants have reduced leaves and reproduce by spores, not seeds.
Life Cycle Moss prefers to grow and become established in the winter with growth peaking in early, wet springs. If grass is established in the fall, moss will fail to compete for space in which to grow. This presents the best strategy for avoiding moss development.
Integrated Pest Management Strategies 1. Cultural practices to inhibit moss growth and stimulate growth of desirable healthy lawn grass. A. Test soil for pH and nutrient content. If deficient in nutrients, follow recommendations of soil test. Fertilize with nitrogen just before the growth cycle. B. Improve drainage. In moist areas with poor drainage, add soil or contour the area to move water away from low lying areas. C. Increase light penetration. Trim lower branches of shade trees and thin to improve light penetration to the soil surface and improve air circulation. A ground cover may be used in lieu of grass if shade is too intense. D. Loosen compacted soils. Compacted soil should be tilled or core aerated to reduce compaction. Loosening the top 2 to 4 inches of soil will help. Cultivation breaks up the algae crust or moss mats. 2. Manual removal. Remove as much of the moss as possible by raking or dethatching. 3. Treatment.Treat the mossy areas with iron compounds; liquid ferric sulfate is the most effective. Fertilizers with iron compounds also work if very fine, near-dust formulations are used. Moss killers containing zinc sulfate will kill the moss but can also damage grass. Buy only products which state "for controlling moss in lawns" as some are for removal of moss in sidewalks and roofs and can be harmful to other plants. Lime and copper sulfate are ineffective in killing moss. 4. Turf selection. In shaded, well-drained soil, plant fine fescues. For shaded, moist areas, plant rough bluegrass. Neither grass, however, will survive extremely heavy shade or soil saturated for long periods. 5. Watering. Keep grass in good condition in the summer by watering deeply to establish deep roots. If an automatic watering system is used, water plentifully once or twice a week (1 inch per watering).
Organic Strategies Strategies 1.B, 1.C, 1.D, 2, 4, and 5 are strictly organic approaches. Strategy 1.A could be considered an organic approach if an organic fertilizer is used.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Crabgrass is an annual grassy lawn weed that spreads along the ground creating a dense mat that smothers desirable grasses. It was introduced from Eurasia and is widespread throughout the United States.
Symptoms and Diagnosis There are three crabgrass species commonly found as weeds in lawns - hairy crabgrass (Digitaria sanguinalis), southern crabgrass (Digitaria ciliaris) and smooth crabgrass (Digitaria ischaemum). All three species are pale green, have a prostrate or ascending growth habit, and have flat 5-10 mm wide blades. The seed heads have 2-6 branches with 2 rows of seeds along each branch. Crabgrass may be found in a wide variety of landscape settings but grows best in full sun. Life Cycle Crabgrass is a warm season annual grass that overwinters as seeds and germinates when soil temperatures in mid spring consistently remain at 50 to 55 degrees for a number of days in a row. Seeds can continue to germinate throughout the summer if soil temperatures and moisture conditions are adequate. It grows during the heat of summer, sets seeds and is killed by the first frost.
Integrated Pest Management Strategies 1. Practice good cultural techniques to keep lawns healthy and free of drought, nutritional or injury-induced stress. Cool season grasses fertilized in the fall and mid to late spring will go into mid-summer dormancy later and will compete better with the crabgrass. 2. Set the lawnmower at 3 inches high. Taller grass will shade the soil and decrease the germination rate of crabgrass seeds. 3. Pull crabgrass plants before they set seed. One plant can produce 150,000 seeds. 4. Overseed existing cool season lawns in the fall. A thick turf in the spring will shade the lawn, retard seed germination and better compete with any germinating weed plants. 5. Apply corn gluten meal herbicide about two to three weeks before crabgrass seeds begin to germinate. In Missouri, this would be between mid March to mid April or about the time when forsythia first begins to bloom. Corn gluten will inhibit the germination of turf grass seeds and should not be used within six weeks of reseeding a lawn. Corn gluten is only about 65% effective compared to synthetic products but is an organic control. 6. Apply a pre-emergent crabgrass herbicide about two weeks before crabgrass seeds begin to germinate. In mid-Missouri, this would be between mid March to mid April or about the time when forsythia first begins to bloom. Applying a pre-emergent herbicide after the crabgrass has begun to germinate will not provide good control but may inhibit seedlings at the 2-leaf stage or seeds that are slower to germinate. Products that combine pre-emergent herbicides and fertilizer are not recommended. Read and follow label directions carefully. 7. Apply a post-emergent crabgrass herbicide if a pre-emergent herbicide was not used or if it was ineffective and control is warranted in early summer. Read and follow label directions carefully. 8. Do nothing in late summer. Crabgrass is an annual grass that will be killed by frost. Applying a post-emergent herbicide in late summer may not be warranted as the first frost will kill it. Next year apply a pre-emergent in early spring to prevent new seedlings.
Organic Strategies Strategies 1 - 5 are strictly organic approaches.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Bamboos are divided into clumpers or runners, which can have a major impact on how well behaved they will be in your garden.
Clumping bamboos Clumping types have a very short rhizomatous root structure and are incapable of expanding more than a few inches a year and will generally form discrete clumps. The clumps slowly enlarge as new culms emerge every year, and may require anywhere from 2-10 feet or more of space in order to reach their mature height, depending on species. Except for species of the genus Fargesia, the clumpers tend to be less cold-hardy than runners. Clumping bamboos generally do not require control. They may be shaped by removing new shoots at soil level when they begin to encroach more closely on nearby structures.
Running bamboos Running types spread by sending out underground runners, or rhizomes, which sometimes emerge far from the parent plant. Runners fill in the spaces between plantings faster, making them ideal for screens, hedges, and the popular open grove look. Runners may be contained, as described below, since the rhizomes grow sideways at a depth of about 2-18 inches. Many are cold-hardy. Following are some strategies you can try for containing and eradicating running bamboos.
Integrated Pest Management Strategies 1. Contain the running bamboo with a physical barrier. The safest containment methods for running bamboo are 1) Planting in containers, or 2) Installing a vertical 30-40 mil thick plastic rhizome barrier 22-30 inches deep around the perimeter of the area in which the bamboo is to be contained. The advantage of this material is that even large plantings of bamboo can be surrounded with a single length of plastic, requiring only one seam. It is preferable to cement (which often develops cracks), or metal (which rusts and requires many seams), is less expensive, and lasts 20-30 years if installed properly. Please refer to The American Bamboo Society for detailed installation instructions. 2. Cut off unwanted shoots. The active growth period usually lasts for only about 2 weeks every spring, then little or no additional new growth will occur until the following spring. Therefore, cut off any shoots you don’t want but remember all of the culms (stalks) of bamboo in a clump or grove are interconnected underground by rhizomes (underground stems). New shoots will grow again next year. If the bamboo in your yard comes from another’s yard, separate your grove from his by cutting the connecting rhizomes, which are usually quite shallow. If this isn’t done, and his part is healthy and vigorous, the rhizomes in your part will still be supported by the photosynthesis in the leaves of his part, and your efforts will be in vain. Cutting rhizomes with a spade or a saw will do the trick if it is done every year. If the growth is old, you may need to use a mattock or a digging bar the first time. Digging a ditch and putting in a barrier is a more permanent solution. 3. Mow unwanted shoots in lawn areas. If the bamboo is surrounded by lawn, then just mow frequently over the area where the bamboo is coming up during the spring shooting season. 4. Many years of effort may be needed to eradicate running bamboo. Begin by either digging as much of the root system out as possible – no easy job – or cutting the bamboo to the ground and then continue by following up with regular removal. New shoots will come up from the rhizomes. Break them off or cut them off with pruning shears. Keep doing this until no more shoots come up. This will exhaust the energy stored in the rhizomes underground. Without green leaves to photosynthesize and produce new energy, they will no longer be able to send up new shoots. The rhizomes will be left behind, but will rot away. This is a slow, labor intensive process. 5. Using chemical weed killers may be helpful. Be warned bamboo doesn't respond well to any herbicide currently on the market. If glyphosate (Round Up) is used, remember it is taken in through the leaves only, and it must be applied in an undiluted form. Often the plants will still re-shoot. Some have used a “cut and paste method” with some success. Each culm is cut to within 6” of the ground and immediately (within 15 seconds) painted with concentrated glyphosate. It has been noted that imazapyr (Arsenal) is more effective on bamboo than glyphosate. However, imazapyr has a great deal of foliar and soil activity and can be very harmful to nearby hardwood trees, shrubs, and all grasses if their roots extend into the vicinity of the application. Therefore, if the bamboo is growing near any desirable plant species, imazapyr should not be used. Glyphosate does not have soil activity and will only kill plants that are contacted with the spray solution. This makes glyphosate a more useful herbicide option for most areas where bamboo grows. It is important to note that one application of glyphosate will not eradicate bamboo. It will most likely be necessary to mow and spray as many as 4 times for complete bamboo control to be achieved. Persistence is key when targeting running bamboo.
Organic Strategies Strategies 1, 2, 3, and 4 are strictly organic approaches.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
There are nearly 5,000 different species of rust of which about 10 may be important pathogens on turfgrass. They attack only live grass plants, and two or more rusts may attack the same grass plant at the same time. Different races of the pathogens occur and they differ in their ability to attack cultivars (varieties) within a grass genus or species. This is one of the reasons that some grass cultivars lose their rust resistance after being grown for a period of years. Rusts in the genus Pucciniaoccur on all commonly grown warm- and cool-season turfgrasses, and a few are responsible for significant stand losses. Among warm-season turfgrasses, zoysiagrass lawns are often the target of severe rust damage, while bermudagrass, St. Augustine grass, and centipede grass lawns are far less likely to suffer serious injury. Perennial ryegrass is the most susceptible of commonly grown cool-season turfgrasses, but the disease is rare on tall fescue and bentgrass. With few exceptions, the host range of rust fungi is limited to a few turfgrasses. Symptoms and Diagnosis Diseased plants initially develop light yellow flecks on the leaves. As the spots enlarge, the surfaces of the leaves rupture, exposing masses of powdery, brick red spores. Continuous heavy infection causes many grass blades to turn yellow, wither, and die. A severely rusted lawn may winterkill. From a distance, rust-infected turf appears dull yellow or light brown. Individual plants may die and the turf becomes noticeably thin. The disease tends to be more severe in partially shaded areas, such as under trees or along fences.
Life Cycle The cycle of development for the rust fungus is very complex because of the many species involved and the numerous alternate hosts, mostly woody shrubs and herbaceous ornamentals. Alternate hosts are not believed to play an important role in the disease development of the fungi that attack turf grasses. The rust fungi may overwinter in infected plants or be reintroduced into lawns each summer by windblown spores. Each spore must come in contact with a water droplet on the leaf or stem surface to germinate and infect the plant. Infection of leaf blades is favored by moderate temperatures (68 degrees to 85 degrees F) and extended wet periods. This cycle is repeated about every two weeks under conditions favorable for rust development.
Integrated Pest Management Strategies 1. Fertilizer. Use a balanced fertilizer at recommended levels, according to a soil test. Low nitrogen levels and nutrient imbalance can encourage rust. 2. Mowing. Mow regularly to remove infected leaf blades before the spores are produced. Avoid mowing lower that the recommended height, as this can lead to stunted root systems and decrease the ability of the turf to withstand drought. 3. Watering. Water early in the day to allow the leaves to dry before night. Avoid water stress by irrigating during dry periods. 4. Cultivars. Select resistant cultivars. Before seeding, consider recommended cultivars that are resistant to rusts.
Organic Strategies Strategies 2, 3 and 4 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Pythium blight, also called cottony blight or grease spot, is a fungal disease of turfgrasses. All turfgrasses, warm and cool season, are susceptible to attack. This disease is most common during hot, very humid weather especially in golf courses, less so in home lawns. The disease can spread rapidly, killing large areas of seedling or established turf in as little as a day during conditions of high temperature (80 degrees to 90 degrees F), high soil moisture, and little air movement. The disease can also occur at lower temperatures during cool (55 degrees to 65 degrees F) wet weather. When root and crown tissue is attacked, Pythium root and crown rot results. This disease occurs mostly during warm to hot weather. Wet, humid conditions favor the disease.
Symptoms and Diagnosis Pythium blight is most readily recognized as small spots or patches of blighted grass that suddenly appear during warm, wet periods. In the early stages, the grass leaves may appear water-soaked, slimy (greasy), and dark. As the disease progresses, the leaves shrivel and the patches fade from green to light brown. When observing these patches in early morning, cottony fungal growth can usually be seen on the foliage, although not always. In many cases, these patches develop into diffused streaks that follow water drainage patterns or mowing patterns. These streaks are caused by the water or equipment picking up the fungus and spreading it along its path. Under favorable conditions for the disease development, these streaks may coalesce to form large areas of dead grass. If a sudden drop in temperature or humidity or the application of a fungicide halts the development of Pythium blight, distinct strawcolored spots develop. Grass blades may twist and collapse at the lesion.
Life Cycle The pathogen survives over winter and periods adverse to disease development as spores associated with debris in the soil. It can be moved from one area to another by soil movement, by transporting diseased plants or plant parts, and by equipment, shoes, or surface water. Damping-off, seed decay, or a seedling blight of turf grasses can also be caused by Pythium fungi. These fungi may also attack the plant roots and crowns, causing reduced growth, off-color, and thinning (Pythium root and crown rot). Diseased plants serve as infection centers from which the pathogen spreads. Movement from these areas can be rapid in wet or humid, hot weather. High nitrogen fertility favors the disease on many grass varieties. Alkaline- or calcium-deficient soils also tend to favor the disease.
Integrated Pest Management Strategies 1. Fertilizer. Maintain grass growth by low to moderate rates of balanced fertilizers. Maintain soil pH in the neutral to slightly acid range. Test the soil every 3–5 years to understand and correct nutrient deficiencies. 2. Watering. If your lawn has the disease, do not water in the late afternoon or early evening. Generally speaking, water in the early morning. 3. Thatch. Remove thatch when greater than 1/2 inch. 4. Pruning. Selectively prune trees and shrubs growing near the area to improve air circulation. 5. Mowing. Increasing the mowing height and following other practices that promote good root growth will lessen damage from Pythium root rot. 6.Fungicides. A preventive fungicide program may be needed to stop the development of Pythium during extended periods of warm, humid weather. Applications of fungicides recommended for control of Pythium blights should be made to areas with a history of Pythium activity when conditions are favorable for development or when symptoms first appear. Repeat applications as necessary. Fungicide applications may be needed 7 to 21 days after planting to protect young seedlings and more often during high rainfall periods. Pesticides registered for use include chlorothalonil (Daconil), fosetyl-Al, mancozeb, and maneb.
Organic Strategies Strategies 2, 3, 4 and 5 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Necrotic ring spot, Leptosphaeria korrae, and summer patch, Magneporthe poae, are two serious, fungal root and crown rots of Kentucky bluegrass, annual bluegrass, fescue, and bentgrass. These diseases were previously referred to as Fusarium blight syndrome. Necrotic ring spot and summer patch cause identical symptoms and cannot be easily distinguished in the field.
Symptoms and Diagnosis NECROTIC RING SPOT is most common in cool weather. It usually occurs during the months of March through May, and September through November. Symptoms consist of dead circles or arches that range in size from several inches to several feet in diameter. Often, the disease will create a frog-eye or a doughnut-shape in the lawn. A frog-eye is a small, circular patch of green lawn surrounded by a ring of dead or dying grass. Microscopic examination of the grass crowns and leaf sheaths may reveal the presence of the dark hyphae of the fungus. SUMMER PATCH is most common in warm weather. Symptoms are present during the months of May through September. The symptoms are similar to those of necrotic ring spot, consisting of dead circles and arches that range in size from several inches to several feet in diameter. The summer patch fungus also produces the microscopic, dark hyphae on the surface of the grass crowns and the leaf sheaths. These hyphae tend to be larger than those found with necrotic ring spot, but are much less common on the plant tissue. When plants with summer patch are dug up, the roots are dark brown to black, hard, and dry-rotted in contrast to the white color of healthy crowns and roots.
Life Cycle Necrotic ring spot fungus survives in soil and infects the crown and roots of grass plants. It commonly occurs when wet weather is followed by hot, dry periods. The range of temperature and moisture conditions at which this disease develops is much broader than that for summer patch, so disease outbreaks can occur from mid-spring through late fall.
Integrated Pest Management Strategies 1. Fertilizer.Use 1 to 3 lbs. of actual nitrogen per 1000 sq. ft. Apply nitrogen fertilizer in the fall (September through November). Do not apply even small amounts of fertilizer during the June- August stress period because this will tend to stimulate the disease. Therefore, fertilize only in autumn (September through November). Maintain a pH above 6.2. 2. Thatch. Thatch (the layer of organic matter between the mineral soil and the green grass) should be no more than 1/2 inch in thickness. Thatch can be removed by vertical slicing machines and/or aeration during the spring and early fall. Over a longer period, thatch will be reduced by using good cultural practices. 3. Mowing. As the cutting height of turf is decreased, its susceptibility to disease increases. Consequently, cut lawns at 2- to 3- inch height and often enough so that less than 1/3 of the leaf blade is removed during each mowing. 4. Watering. Deep watering is essential for proper root growth. More frequent watering provides an ideal environment for disease development. Soaker hoses are very useful for supplementary watering on steeper slopes where sprinklers are inefficient and apply water too fast. The harmful effects of excessive temperature can be reduced by a light sprinkling of the surface at midday. 5. Cultivars.Select resistant cultivars. Before seeding, consider recommended cultivars that are resistant to necrotic ring spot and summer patch. 6. Fungicides. Chemical treatment is efficient only when good cultural practices are first used. Thoroughly water areas with a history of these diseases several days before applying a fungicide. Apply in early to mid-June and a second application two to three weeks later. Use a preventive fungicide program with recommended fungicides. Read labels for proper fungicides and always adhere to the rates and procedures recommended on the label. Pesticides registered for use include azoxystrobin (Heritage), chlorothalonil (Daconil), iprodione (Chipco), thiophanate methyl (Cleary 3336), and ziram. Organic Strategies Strategies 2, 3, 4, and 5 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Mushrooms growing in lawns are common occurrences especially during rainy weather. They live off decaying organic matter in the soil, often decaying tree roots, and are not harmful to the lawn. They will naturally disappear as they age or they may be collected and composted, knocked down with a rake or hoe, or mowed over with your lawnmower. Mushrooms should never be collected and eaten unless you are expert in their identification. To the novice gardener, many poisonous mushrooms can look very similar to edible ones. Don’t take a chance. Mushrooms that develop in a ring in the lawn are called fairy rings. They will be the focus of the remainder of this sheet. Fairy rings are caused by many different soilinhabiting fungi of the class Basidiomycetes. These fungi can cause the development of rings or arcs of deep green grass as well as unthrifty or dead grass. Fairy ring fungi do not attack grass directly, but break down organic matter in the soil. As a result, nitrogen is released which the grass uses, causing it to grow and develop a contrasting green ring. In cases where the mycelia of the fungus get very dense and inhibit water movement into the soil, grass in the arc may turn brown. Mycelia may also deplete soil nutrients and produce toxic levels of hydrogen cyanide. The mushrooms that appear after rainfall are the fruiting bodies of the fungus. The organic matter fairy rings break down is often old tree stumps, roots, logs, lumber, and other larger pieces of organic material in the soil below the lawn. Once this material is depleted, the fairy ring will disappear. This may take considerable time. Several fairy rings may appear relatively close together, especially on lawns that exist on sites that were previously wooded areas. When this occurs, it becomes noticeable that fairy rings do not cross each other, as fungal activity ceases when fungi from different rings contact each other.
Symptoms and Diagnosis Dark green circles, arcs, or rings of thick, fastgrowing grass develop anytime from green-up in the spring (most common) until the first hard frost in the fall. These rings are most commonly between 2 and 15 feet in diameter, although they may be larger or smaller. Mushrooms or puffballs may appear under wet conditions in the same ring pattern. In some cases, a ring of brown or dead grass may appear.
Life Cycle Approximately 50 species of fungi are known to form fairy rings in turf, with Marasmius oreades, Agaricus campestris, Lycoperdon spp., and Scleroderma spp. being the most common. These fungi decompose organic debris in the soil and thatch. Fairy ring starts from a piece of mycelium or spore at a single point feeding in the thatch layer or on soil organic matter. The uniform outward growth of the fungus results in the development of rings. Under certain conditions, and with certain fairy ring fungi, a ring of dead grass develops. Some of the responsible fungi have been shown to penetrate and kill root cells resulting in dead rings of grass. In addition, the mycelia of some fairy ring fungi are reported to be hydrophobic, creating a waterimpervious layer resulting in drought-stress problems for the grass. Once the soil under this mycelial layer becomes dry, it is very difficult to wet, and the roots of the grass plant die.
Integrated Pest Management Strategies 1. Fertilizer. Use of a nitrogen fertilizer can mask the symptoms of fairy ring by causing the rest of the lawn to green up. Using a soil needle (deep root feeder) to aerate and irrigate dead and dying rings is recommended. 2. Removal. Fairy ring development can be traced to buried organic debris. Undecomposed tree roots, wood scraps from construction projects, and other organic debris are commonly colonized by the fairy ring fungi and should be removed before establishing a new lawn. Use clean, ring-free sod for a new or renovated lawn. Destroying existing turf may be required in persistent cases. Discard or kill a strip of sod 1 to 2 feet wide on each side of the zone of lush turf with a non-selective herbicide. Cultivate the area repeatedly to thoroughly mix the ring and nonring soil. Eliminate dry spots by soaking the cultivated area with water. Reseed or install clean, ring-free sod. 3. Thatch. Eliminate thatch buildup with a dethatching program. 4. Fungicides. Some fungicides are available for suppression of fairy ring, however, they may be only temporary as the decaying material may still be present. Organic Strategies Strategies 2 and 3 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Brown patch (Rhizoctonia solani) is a fungus which attacks most commonly cultivated grasses. Differences in susceptibility exists within cultivars of the various grass species. Bent grass, perennial ryegrass, tall fescue and annual bluegrass are the primary hosts. There are various species of Rhizoctonia which can attack grass plants from seedling stage too mature plants and are pathogenic over a wide range of environmental conditions. Brown patch may also be referred to as Rhizoctonia blight. Large brown patch is used to describe the disease in zoysiagrass.
Symptoms and Diagnosis Symptoms vary depending on the turfgrass species and mowing height. Susceptibility of the cultivar, management practices and weather conditions determine the degree of injury. More than one fungi may also be present in the lawn. As the name suggests, symptoms include small circular patches of brown, lifeless grass. These patches often enlarge and join together, reaching diameters of six feet or more. Newly established lawns may be more severely damaged than established lawns. In warm-season grasses such as zoysia the most common symptom is a circular pattern of brown grass with a yellowish colored ring (smoke ring) of wilted grass at the perimeter of the diseased area. The leaves can easily be pulled from the stolons within the smoke ring because the fungus destroys the tissue at the base of the leaf sheath. First appearing symptoms are small circular patches of water-soaked dark grass that soon wilt and turn light brown. Stolons often remain green. As the disease develops, the circular patches enlarge, become more apparent and new green leaves may emerge in the center of the circular areas.
Life Cycle Mid to late summer is the time when the best conditions are present for disease development. This requires the presence of an active fungi, vigorous growth of a susceptible grass, daytime temperatures ranges between 75 degrees and 85 degrees F, the presence of free moisture on the foliage and night temperatures below 68 degrees F. This fungus feeds on dead organic matter in the soil, but will attack grass when the right environmental conditions arise. Hot, humid conditions promote spread of the fungi. Integrated Pest Management Strategies 1. Fertilizer. Don't fertilize warm-season grasses in early spring and summer, particularly with soluble nitrogen. Use slow-release nitrogen fertilizers. Fertilize to maintain adequate but not lush growth during the growing season. Properly fertilized turf will recover quicker from disease injury than will under-fertilized turf. 2. Collect waste. Remove and dispose of clippings from infected areas or when conditions are conducive to disease development. Mulching mowers that chop clippings to 1/4 inch or less do not contribute to brown patch development. Mow only when the grass is dry, being sure to remove no more than one third of the top growth. 3. Prune. Prune trees and shrubs to allow air movement and light penetration to reach the turfgrass. 4. Watering. Water to a depth of about 6 inches no more than once a week. More frequent watering provides an ideal environment for disease development. 5. Drainage. Provide good surface and subsurface water drainage to reduce humidity in the turf canopy. 6. Fungicide. Use a preventive fungicide program with recommended fungicides. Read labels for proper fungicides and their use. 7. Replant dead areas. The disease can occur quickly, spread rapidly and then stop abruptly as environmental conditions change. Frequently, the best and only recourse is to replant dead areas in warmseason lawns in early summer. Organic Strategies Strategies 2, 3, 4, 5 and 7 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Several fungal diseases attack lawn grasses. Following is a short description of the most common diseases to help you sort out which one may be causing your problem. The diseases have been categorized as patches (cause dead spots or patches in the lawn), rings (cause rings of dead or affected grass), or leaf blight (affect individual blades of grass, often over a wide area and no distinct patch or ring pattern may be noticeable). Since most grass diseases affect leaves, patches and rings describe certain diseases in more advanced stages of development.
Result in Dead Spots or Patches BROWN PATCH (Rhizoctonia solani) Round patches of turf up to several feet in diameter appear watersoaked and eventually turn brown. Dark gray smoke ring is sometimes visible on lower mowed turf. DOLLAR SPOT (Moellerodiscus spp. & Lanzia spp. or Sclerotinia homeocarpa) Rounded, straw-colored, slightly sunken patches up to 2 inches in diameter on bentgrass greens, 4–6 inches in diameter on other lawns. Spots have a reddish margin and expand until they girdle the leaf blade. Cottony mycelium may be evident in the morning growing over dead tissue.
RED THREAD (Laetisaria fuciformis) Pinkish patches from 3 to 15 inches in diameter develop during rainy weather. The grass in the patches is pink and dead and contains coral-red masses of mycelium. The disease is more common in fescues and grows best from 60 to 70 degrees F. SNOW MOLD (Gerlachia nivalis and Typhula spp.) Grayish white patches up to 3 feet in diameter. Grass blades are collapsed and matted. Several different fungi are responsible for snow mold disease. Dead areas appear in the turf after the snow has melted. PYTHIUM (Pythium spp.) Rounded sunken patches up to 1 foot in diameter. Leaves appear water-soaked and shiny at first, turning tan when dry. White mycelium grows over all leaf tissue, not just dead tissue as in dollar spot.
Result in a Ring in the Lawn FAIRY RING (Marasmius oreades and others) Dark green ring with lighter green center, 2 ft to 100 ft in diameter. A mycelium starts in one spot and spreads in all directions. At certain times of the year, the fruiting bodies, mushrooms, may develop near the outer borders of the year’s growth of mycelium. The grass within the ring may appear to be healthy but later may collapse and die. NECROTIC RING SPOT (Leptosphaeria korrae) 1–3 patches of red or purple leaves that bleach with water stress. Many patches grow greater than 12 inches in diameter with weeds or resistant grasses forming frog-eyes in the center of the ring.
SUMMER PATCH (Magnaporthe poae) Small tan or straw-colored spots appear on the leaves in early summer. These spots enlarge and coalesce until large areas of the lawn are killed. This disease is active only during the warmest part of the summer. Affects Scattered Leaves POWDERY MILDEW (Erysiphe graminis) Powdery mildew appears as dirty spots or blotches on the leaf sheaths, varying in color from light gray to brownish. It is especially prone to develop in wet weather and on poorly drained lawns. The infection spreads by the numerous white spores, which form on infected leaves.
LEAF SPOTS (also called Melting out, various organisms) Many grasses are affected by leaf spot diseases. General symptoms include tan or strawcolored spots on leaves usually bordered by a darker color. Black spore-producing structures may be seen in the center of the spots of some diseases. RUST (Puccinia graminis var. agrostis) The disease appears as small, reddish spots on the leaves. Merion bluegrass, a special strain of Kentucky bluegrass, is very susceptible to this disease.
ANTHRACNOSE (Colletotrichum graminicola). This disease is common on creeping bentgrass and annual bluegrass. The fungus causes individual grass blades and/or plants to yellow and die when it invades crown and root tissue. Black, hairy, and spiny fruiting bodies are abundantly produced on dead tissue but may also be seen on green leaves as well.
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