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There are thousands of silent and unseen life forms lurking in your garden. The first hint of their presence might be a mysterious yellowing of your lawn, red or brown spots appearing on the plant leaves. There are over 50,000 different types of plant disease looking for a place to call home, and it’s almost certain that your lawn and landscape plants are host to some of them. Plant disease can be very serious and economically damaging.

Based on their causes, diseases are divided into two groups: no parasitic or parasitic diseases. Non parasitic disease is the result of some genetic or environmental factors like nutrient deficiencies, extreme cold or heat, mechanical injury, or lack of water. This type of disease is not transmitted to healthy plants and control depends on correcting the condition which causes the disease. Parasitic disease is caused by living organisms which survive and spread by infecting other plants. The three biggest groups of parasites are fungi, bacteria and viruses. Many diseases make regular appearances at certain times of year or during particular combinations of temperature and rainfall.

Our experience with disease allows us to quickly identify most of the more common varieties. Sometimes, though a simple visual inspections isn’t’ enough to give us a positive identification. With so many disease possibilities, it’s difficult to be familiar with them all. When the disease type isn’t obvious, the most important fact needed is the name of the plant being affected. The plant variety can then be looked up in lists of known plant diseases and the symptoms compared. How much of the plant is affected? Parasitic diseases usually do not infect large portions of a plant in the early stages, and they don’t normally infect several different plant varieties at the same time.

The key to controlling any disease is to interrupt its life cycle in some way. This could be changing the growing environment or using plants which are resistant to the disease. Keeping you landscape well fed and properly watered helps discourage disease infections, but even the healthiest and best cared for properties can be badly marred by disease if left untreated. The most practical control when disease activity becomes serious if often to place a protective chemical over the surface of the plant.

Treatment programs can be either preventive or curative. Scheduled preventive programs are desirable because the require less material while keeping your landscape healthier. If you have any questions or concerns about diseases and their control, please don’t hesitate to give us a call.

Brown Patch is most common to Kentucky Bluegrass, Bentgrass, and ryegrasses in regions with high humidity and/or shade. Brown patch commonly starts as a small spot and can quickly spread outwards in a circular or horseshoe pattern up to a couple of feet wide. Often times, while expanding outwards, the inside of the circle will recover, leaving the brown areas resembling a smoke-ring.

Control
When environmental conditions are favorable, brown patch is likely to develop on susceptible turf grasses. The severity of the disease can be somewhat controlled by following a strict fertilization schedule that only apply the proper amount of nitrogen and trace elements during the ideal times; by watering early in the morning to remove dew and all the grass to dry quickly; mow grass a little taller with a sharp mower blade, and when possible , by bagging the lawn clippings during likely periods of disease activity. Fungicide applications are most effective when used as a preventative before the disease has become established in the lawn.

Prevention
The best prevention for brown patch is to aerate often, reduce shade to effected areas, and follow a fertilization schedule to help prevent fertilization with excess amounts of nitrogen.

Treatment
The most common fungicides used on Brown Patch are: benomyl, and chlorothalonil.

Spotting Brown Patch
Brown patch symptoms can vary depending on the grass variety, the soil as well as climate.

Typically, brown patch causes rings or patches of blighted grass that measure from 5" to more than 10' in diameter. It also causes leaf spots and thin rings with brown borders around the diseased patches.

After the leaves die in the blighted area, new leaves can emerge from the surviving crowns. On wide-bladed species, leaf lesions develop with tan centers and dark brown to black margins.

Bown patch favors high humidity and temperatures over 85 degrees during the day and not below 60 at night. It also occurs in areas that receive more than 10 hours a day of wetness for consecutive days.
Brown patch infestation is more severe when the grass is cut to a height less than the optimum for the variety of grass.

Dollar Spot, caused by the fungi Lanzia spp. and Moellerodiscus spp., produces 23 inch circular patches on creeping bentgrass turf and 4-6 inch circular to blotchy areas on bluegrass lawns. These patches are straw colored. Early in the morning, when the grass is covered with dew, a faint cobwebby growth may be seen on the leaves of affected plants. In the early stages of disease, leaves develop distinct tan-colored spots and bands; quite often a reddish-brown border can be seen on the leaf spots.

Dollar Spot develops at temperatures of 60-85 degrees Fahrenheit with high humidity and low soil moisture. The disease usually develops on lawns which are unfertilized but occasionally occurs on high maintenance lawns under stress. It can be controlled by keeping lawns adequately fertilized and watered and by using a fungicide as necessary. Bluegrass varieties differ in Dollar Spot susceptibility with most being moderately susceptible or moderately resistant.

Dollar spot affects small, circular areas of turf, about 1" — 5" in diameter. Spots may merge to form large, irregular areas. Leaves appear water-soaked initially, then brown and often exhibit a reddish band extending across the leaf. Lesions on leaves often have a distinctive "hourglass" shape with necrosis on the outer edges of the leaf blade and healthy tissue in the middle. Fine, white, cobwebby hyphae (fungal threads) may be seen in early morning. The fungus survives as mycelia or stromata (dark, tiny, hard, resting bodies) on plants or in plant debris during periods of unfavorable weather conditions.

Susceptible turfgrasses
Bentgrass, bermudagrass, fescue, ryegrass and annual bluegrass can be affected, but closely mowed grasses of any of these species are most susceptible to the disease.

Conditions favoring this disease
Dollar spot is most common during the spring and fall months especially on annual bluegrass, Kentucky bluegrass, and creeping bentgrass used in coastal plantings. Disease development is favored by moderate temperatures (60° — 80°F) with high relative humidity. Excessive leaf wetness and fog contribute to disease development as do water stress and excess thatch development. Dollar spot is primarily a problem on golf courses and lawn bowling greens.

Management
Proper fertilization and irrigation as well as adding compost are important in preventing the development of dollar spot. Fungicides may be necessary to provide control if the disease develops.

Cultural Control
Turfgrass deficient in nitrogen tends to develop more dollar spot than turfgrass adequately fertilized. Apply recommended amounts of nitrogen and maintain adequate air circulation. Keep thatch to a minimum. Irrigate based on evapotranspiration needs of the turfgrass to a depth of 4"— 6", but avoid creating drought stress by extending the interval between irrigations too long. Raise the mowing heights as much as possible.
Avoid prolonged leaf wetness by irrigating in the morning or early afternoon rather than later in the day. Remove morning dew with a light irrigation or poling. Poling involves dragging the surface of the turf with a long bamboo or plastic pole, or with an irrigation hose, to remove the dew from the grass leaves. Some varieties of creeping bentgrass show higher levels of tolerance to this disease than others. Varieties such as Putter, Emerald, Forbes 80-12, SR-1020, Penneagale, Penncross, Century and Crenshaw are quite susceptible to dollar spot, while varieties such as L-93, A-1, Providence and Pennlinks have shown tolerance to this disease.
Adding composted top dressings has been shown to reduce the incidence and severity of dollar spot, allowing a reduction in the frequency and/or application rates of fungicides.

Treatment Decisions
Apply fungicides when environmental conditions favor the development of the disease, or when the first symptoms are detected. Apply until environmental conditions are no longer favorable for the disease.

The disease formerly called "Fusarium Blight" or "Fusarium Blight syndrome" was once thought to be a distinct disease characterized by patches of grass that develop "frog-eye" patterns. These consist of donut-or crescent-shaped areas of dead or dying grass with a center of green grass. Now this disease is recognized to be a complex of rather similar appearing diseases that include Necrotic Ring Spot, Rhizoctonia Yellow Patch, and Summer Patch

Leaf spot and melting out are among the most frequent and destructive lawn diseases of common bluegrass. Melting out is caused by the fungus Drechslera poae and leaf spot by the fungus Bipolaris sorokiniana. Excess thatch, heavy nitrogen fertilization, excess shade, mowing too close, and broadleaf herbicides promote these diseases. The melting out pathogen, D. poae, can also cause leaf spots. Conversely, the leaf spot pathogen, B. sorokiniana, can also causing melting out symptoms.

Leaf spot occurs in warm weather and is easily recognized. Spots on the leaves develop purplish-red to purplish-brown borders and brown to tan centers. The spots may extend the width of the leaf and are somewhat longer than wide. Leaf spots may cause the death of leaf tips. Leaf sheaths are also infected, and may die, resulting in thin stands of grass. Melting out begins as spots on the leaf blades and rapidly moves down the leaf sheath and into crowns and roots. In advanced stages, when many plants die in a large irregular patch, it is known as "melting out". These patches may range in size from several inches up to many feet and may produce an irregular patchwork across an entire lawn.

Once established, melting out is difficult to control. Proper watering and fertilization for bluegrass varieties in your lawn will reduce the danger of melting out. Common Kentucky bluegrass should not be fertilized as heavily as the elite blue grass varieties or high maintenance diseases will develop. It is particularly important to avoid excess use of nitrogen fertilizer and evening watering. Remove excess thatch — the layer of plant material tightly interwoven with living tissue between the soil surface and the green vegetation. Fungicides may be needed to control leaf spot disease. Their effect is temporary and beneficial only when combined with a change in cultural practices. Fungicides are most effective if the initial application is made when leaf spot first becomes serious and less effective when small patches of lawn begin to die. When large areas of a lawn are dying or dead from melting out, dead patches should be reseeded with a resistant variety. Bluegrass varieties differ in their susceptibility to melting out. Older common bluegrass types are often very susceptible while newer elite varieties are usually quite resistant.

Powdery Mildew is a common problem on bluegrass lawns in shady areas. The mildew fungus, Erysiphe graminis, attacks the surface of the grass leaves, developing a fine, fungal growth that resembles a white powdery substance on the leaves. In dense shade, Powdery Mildew causes the affected areas of leaves to turn yellow, eventually resulting in the yellowing and dying of lower leaves or even in the death of plants.

Powdery Mildew develops in areas of dense shrubbery or trees where there is poor air circulation, considerable shade, and high humidity. It is favored by temperatures of 60-72 F. In many cases, Powdery Mildew can be controlled by selective pruning of shrubs to allow better air circulation and greater penetration of sunlight. Where Powdery Mildew is a problem, avoid susceptible grass varieties or plant alternate ground covers.

Sometimes mushrooms will develop and form large circles in lawns. Each year the circle expands. When these circles or "Fairy Rings" are small there may be no effect on the grass, but as they continue to expand, a zone of stimulation forms where the mushrooms come up. Inside this is an area of poor grass growth, or even dead grass. This is the zone of inhibition. Another zone of stimulation may occur inside the dead or dying zone.

Fairy Rings are unsightly but very difficult to control, and the average homeowner may prefer to live with the problem. One way to eliminate Fairy Ring is to dig it out, although this is seldom practical. Mark out an area at least one foot beyond the ring and remove all sod in that area. Then remove all the soil in that area to a depth of one foot, being careful not to spill any on the lawn. Refill the hole with new soil and reseed or resod. Seeding is preferable as there is less danger of reintroducing the Fairy Ring fungi. Doing this job without spilling any soil and reintroducing the Fairy Ring fungi is extremely difficult.

For those who decide to live with the problem, there are several ways to minimize damage to the grass in Fairy Rings. The grass should be fertilized with nitrogen several times a year to help mask symptoms. Most of the Fairy Ring growth (a fungal mat) is in the ground underneath the Fairy Rings, and this growth causes the soil to become nearly impervious to water. Using a "root feeder" attachment on a garden hose, punch holes at least every foot in the yellowing or dying area and pump large amounts of water into the ground to a depth of 10-24 inches. Repeat frequently. Increasing the soil moisture may also change the ecological balance enough to retard the growth of the Fairy Ring fungi. Application of a wetting agent to the area may also increase soil permeability and help to lessen symptoms. Aeration also reduces the symptom severity.

Pythium Blight, caused by Pythium spp., occurs during hot, humid weather. Circular to irregular spots appear -- initially 1-6 inches in diameter. Early in the morning these spots have a greasy green or water soaked appearance, and the grass feels slimy or greasy. Later the grass in these spots dies and the dead grass becomes light tan and shriveled. The affected areas may have a matted appearance and a cottony white growth may develop on the dead leaf blades during wet periods. Grass blades at the edges of dead patches may have straw-colored borderless lesions. This lack of a dark brown border on lesions distinguishes Pythium lesions from the lesions of Dollar Spot. If the grass was mowed while wet, Pythium Blight may be spread by mowing and develop in irregular streaks and patches in the direction of mowing. Pythium Blight also tends to follow drainage patterns.

Pythium Blight is most severe with day temperatures of 84-95 F and night temperatures above 68 F. The disease is more severe on heavily fertilized cool-season grasses. Wet soil and thatch also favor the disease. A film of water on the leaves is necessary for infection.

Control of Pythium Blight requires careful water management. Avoid excess water or watering late in the day when the plants may stay wet all night. Do not mow when the grass is wet, especially in hot weather. Avoid excess fertilizer, especially nitrogen fertilizer in hot weather. If the thatch is over 1/2 inch thick, remove excess thatch by dethatching. No fungicides for Pythium control are readily available to the homeowner, but several commercially applied products are very effective.

Red Thread caused by the fungus Laetisaria fuciformis, is favored by cool, humid weather. Red Thread may become more common on lawns with fescue and ryegrass blends. Red Thread causes the lawn to have a bleached patchy appearance. Irregular areas, from several inches to several feet across, develop a whitish to pinkish color. Leaf blades and sheaths are attacked; at first they develop water-soaked or greasy green areas, then the affected parts dry out and become tan-colored. In wet weather the affected leaves are covered with a gelatinous pink fungus which then forms bright red threadlike strands near the tips of the leaves and from leaf to leaf.

The best temperatures for Red Thread development are 68-75 F. Red Thread can be quite severe on red fescue (a component of many shade-tolerant lawn grass mixtures) and may occasionally be severe on bluegrass.

Control with fungicides is not usually required for Red Thread. If soil nitrogen levels are low, fertilizing the lawn may help it to recover more rapidly. Deep watering and avoiding frequent light waterings, especially in late afternoon, may help to reduce damage. Collect grass clippings when the disease is active.

Rust, caused by Puccinia spp., is not seen every year, but sometimes becomes severe on susceptible varieties during hot periods of the summer when grass growth is reduced. When rust is severe, the lawn may have a yellowish to reddish-orange appearance. A red-orange dust fills the air when the grass is mowed and also collects on shoes and clothing. Individual blades of grass will have slightly elongated yellow-orange to red-orange spots or pustules (filled with a rusty colored powder -- the spores of the rust fungus) that break through the leaf surface. When rust is severe, the grass blades turn yellow, wither and die. Rust may also weaken a lawn, making it more susceptible to winter kill the following winter.

Rust is favored by humid weather with night temperatures of 70-75 F, day temperatures of 85-95 F, wetness from dew lasting many hours after sunrise, and frequent light rain (or watering). Rust may be especially severe on Merion and Touchdown varieties of bluegrass, which are highly susceptible. When weather favors rust, the disease is more likely to be severe on low maintenance lawns -- lawns with low soil fertility and some degree of drought stress. It is also apt to be a problem in shady areas, on closely cut grass, and on newly laid sod.

Rust is easily controlled by maintaining good lawn growth with adequate fertilization and adequate watering. Once normal growth is obtained, mow the grass frequently at recommended mowing heights and remove the clippings, an important source of the rust fungus. Fungicides are not usually needed or economical for homeowners, but may be required to help protect new growth when rust is severe and weather promotes rust development.

The snow molds usually appear in the spring as the snow melts from lawns. There are two common types of snow mold: Typhula Blight and Fusarium Patch. They usually can be distinguished by their symptoms, develop under slightly different conditions, and are controlled by different fungicides. Typhula Blight is caused by the low temperature fungi, Typhula incarnata and T. ishikariensis, especially active under the snow covering unfrozen ground.

Typhula Blight damage first appears when the snow is melting. Roughly circular patches 2 to 40 inches or more in diameter develop. These patches are straw colored, and enlarge as long as the grass remains cold and wet from melting snow. The grass in the patches has a matted appearance, and may have a visible gray colored mold growth on the whole patch or on the advancing margin. Hard fungus bodies called sclerotia develop on or are imbedded in the leaves and crowns of affected plants. These sclerotia are more or less spherical in shape. The sclerotia of T. ishikariensis are the size of a pinhead and black; those of T. incarnata are up to 3/16 of an inch in diameter and brown. These sclerotia's presence help diagnose Typhula Blight.

The Typhula fungi survive the summer in the soil or thatch as sclerotia. Active growth of the fungus resumes in the absence of light under snow cover on unfrozen ground. Growth takes place at temperatures as low as freezing (to slightly below freezing) and continues after snow melt in the spring for as long as the grass remains wet and the temperatures cold. Typhula activity stops when the temperature exceeds 45 F or the surface is dry.

Management practices for control of Typhula Blight are similar to those for Fusarium Patch. Fungicides are seldom needed in bluegrass lawns.

Pink Snow Mold

The web-like mycelium of pink snow mold (Microdochium nivale) may initially look white and mature to a faint pink to salmon color. The pink snow mold fungus does not produce sclerotia.

It is useful to determine whether the disease is pink or gray snow mold because gray snow mold rarely damages more than the blades of the grass. Lawns with gray snow mold can be expected to recover fairly quickly even when damage appears extensive. Pink snow mold, in contrast, may invade the crowns and roots causing more serious injury. It is not unusual for both types of snow mold to be found in the same area. All common lawn grasses may be infected, but Kentucky bluegrass-fescue lawns are the least susceptible to severe damage.

Season:
Pink snow mold may be active in cool, wet conditions from late fall through early spring even in the absence of snow or other covers, a factor which greatly enhances its potential as a damaging disease.
Disease Cycle:
Snow mold fungi remain inactive during the warm months when other disease fungi are most active. They survive in thatch and on plants as sclerotia (gray snow mold) or as mycelial threads (pink snow mold). In the fall, Typhula species sometimes produce small, white or pinkish, club-shaped spore-producing structures that may be seen among grass blades in lawns that have not been recently mowed. They grow from sclerotia that were produced in the previous winter for survival over the summer.
As cool, wet weather develops, the fungi begin to grow and infect grass plants. Like all living organisms, these fungi require moisture to survive. The cold, dry air of winter prevents active growth. The shelter of leaves, snow or any other cover on the grass maintains the necessary moisture for growth. Optimal conditions for snow mold activity occur when snow falls suddenly and remains on ground that has not yet frozen. In such cases, grass is often still lush, providing an excellent food base for the fungi. Mold may renew activity if cool, moist weather conditions prevail and may warrant treatment.

Summer Patch, caused by the fungus Magnaporthe poae, is less common on Kentucky bluegrass. It is a disease that occurs during the hot portion of the summer. The initial symptoms are yellow patches 6-12 inches in diameter. The turf in these patches thins and the remaining turf turns bronze in color. If warm weather continues, all of the turf in the patch may die. The dead patches may be colonized by weedy grasses.
Soil moisture is important in disease development. Excess irrigation or an absence of irrigation during hot weather may make the disease more severe.