Gary Y. Gao
Joseph F. Boggs
Pamela J. Bennett
Jane C. Martin
Joseph W. Rimelspach
James A. Chatfield
This article is compiled from reports of turf cultural and disease problems in the weekly Buckeye Yard and Garden Line throughout the year of 1997. Many turf problems were related to unusual weather conditions. Turf problems included winter desiccation, pink snow mold, red thread, summer grass dormancy, brown patch, and dollar spot.
Browning in turf from wind drying and desiccation was reported because snow cover was limited during the winter of 1996-1997. Some Poa annua on golf courses was suffering from "crown hydration kill" due to fluctuating winter temperatures and moisture. Late December was wet with mild temperatures, then temperatures rapidly dropped to -10 degrees F. The crowns froze but stayed green. The previous damage became evident as temperatures warmed in March. Many grass crowns appeared brown and dead in April.
Some lawn areas seeded in the fall of 1996 failed despite the fact they went into winter looking nice and green. This was likely due to fluctuating winter temperatures and moisture.
Yellow and green blotchiness and patterns of uneven coloration were reported on April 15, 1997. This occurred because different turfgrass species and varieties grew at different rates. Some of the taller growing varieties were being cut too short, resulting in yellowing and blotchiness.
"Helminthosporium" leaf spot disease became noticeable in lawns the third week of April, on susceptible varieties of Kentucky bluegrass in poor and compacted soils, or in areas with heavy thatch. Leaf blades were spotting, girdled, and died prematurely. Proper mowing practices and core aerating in spring were recommended to maintain the health of the lawn. In addition, fungicides containing ipridione were recommended for long-term suppression of the disease where treatment was deemed necessary.
Fusarium patch (pink snow mold) was often reported into late May this year, due to the persistent cool weather in many areas. The Plant and Pest Diagnostic Clinic (PPDC) at Ohio State University received samples from numerous locations in northern and southern Ohio and from Pennsylvania, Utah, and California. Samples were most commonly on annual bluegrass from golf courses. In most cases, grasses outgrew this disease as the weather warmed. Where fungicides were necessary, those containing iprodione and vincozolin were used.
In some cases, pink snow mold was reported as late as June 12, 1997. Infections were found on older bentgrass as well as newly established bentgrass, which was an unusual occurrence. Pink snow mold produces circular, water-soaked patches of brown or yellowish-brown grass. The patches, ranging in size from one to eight inches, may have a slightly pinkish hue and exhibit a tinge of orange around the outer edge. Although Ohio State University Extension Bulletin L-187 lists several effective fungicides for control of this disease, rising temperatures and declining moisture levels normally halt infections in the summer. Pink snow mold infection reports had declined by the week of July 3, and turf that experienced damage from this disease had completely recovered due to warmer temperatures and some drying.
Red thread patches started to appear during the third week of May on fine fescues and perennial ryegrass in southwestern Ohio. This disease is usually first noticed when small, circular patches of yellow to light brown grass begin to develop randomly throughout a lawn.
Red thread disease was rampant in lawns with cool and wet weather by the first week of June. The disease produces irregular patches of blighted or browned grasses ranging in size from two inches to three feet in diameter. Water soaked spots appear first, followed by general drying out of the infected tissue. The tissue fades to a tan color. Under damp conditions, leaves may be covered with a pink, gelatinous, threadlike growth of fungus. This growth may extend out from the leaf tips to nearby plants. Control measures include a good fertility program at balanced rates, mowing a bit shorter to promote rapid drying of affected areas, and a fungicide program (e.g., chlorothalonil) if the problem is severe.
During the week of June 17, Rhizoctonia blight was predicted to be a serious problem due to the abundant moisture, especially on tall fescue. Blades start out looking water-soaked and dark bluish-green, then they dry, wither, and turn brown; lesions are evident. Moisture must be present on the leaves for the fungus to spread rapidly to healthy plants. Turf growing under high nitrogen is more susceptible. By July 3, Rhizoctonia brown patch was reported to progress nicely on turfgrass in areas of high temperatures and rainfall.
During the week of July 24, dollar spot was active primarily on bentgrass but also was seen on Kentucky bluegrass and ryegrasses. Symptoms included round, brown, or bleached spots the size of a silver dollar or somewhat larger. Patches on bluegrass are generally larger and not quite as defined. Dollar spot is generally found on sites that are low in fertility and in dry areas. The blighted blades normally have straw-colored tan areas with reddish-brown margins. The fungus reaches peak activity during humid weather when temperatures range from 70 degrees F to 80 degrees F.
Dollar spot was observed on turfgrass at the same sites where red thread occurred. This is not surprising since both diseases are found on turf that is slow-growing and has not been properly watered and fertilized. An application of slow release fertilizer was recommended to encourage recovery. The slow release component should be at least 50% of the fertilizer with about 3/4 pound or less of nitrogen per 1,000 square feet.
Cool season grasses went into dormancy when the weather turned hot and dry in August. Some concerned homeowners incorrectly blamed their neighbors' maliciously spraying lawns and killing them.
During the third week of August, many lawns recovered from their drought- induced state, with the onslaught of rains. Stolons and rhizomes needed to be checked to determine if they were still plump and fleshy. If they were, and if the area was small, recovery and filling in should occur, especially with cooler temperatures and rain.
During the fourth week of August, core aeration of turf was recommended for many lawns. There are many benefits of core aeration if ample soil moisture is present to allow for core removal. Thatch reduction, stronger root growth, and healthier turfgrasses are some of the benefits.
Rust became apparent in Ohio lawns in late August and September. The rust-colored tiny spores of the fungus rub off easily on shoes, fingers, clothes, and even animals romping through the grass. It is most common on Kentucky bluegrass and perennial ryegrass lawns.
Rust causes the turf to take on a generally yellow appearance, and symptoms are more evident when the weather is dry. Alternating conditions of low light intensity, 70 degrees F to 75 degrees F temperatures, and high humidity for four to eight hours followed by high light intensity, 85 degrees F to 95 degrees F temperatures, and slow drying of leaf surfaces favor the development of rust disease.
Control recommendations included using blends of resistant turf cultivars and providing adequate water and fertility levels to keep the grass growing vigorously during dry periods. Fungicide treatments were recommended only if the lawn experienced continuous heavy infections.
Pound, W. E., and J. Street. 1991. Ohio State University Extension Bulletin #546, Lawn Establishment.
Street, J., W. E. Pound, D. J. Shetlar, C. C. Powell, W. W. Shane, S. K. White. 1991. Ohio State University Extension Bulletin 271, Your Lawn.
W. E. Pound, J. Rimelspach, J. Street, D. J. Shetlar. 1997. Ohio State University Extension Bulletin L-187, Control of Turfgrass Pests.