SportsTurf

August 2017

SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.

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A: As turf professionals there is no doubt you have heard this question a hundred times from friends, family, neighbors and fi eld users. Turf goes brown for many reasons and fi guring out why can be tricky. Diagnosing a turf problem involves ask- ing many questions and ideally seeing the turf fi rst- hand or having good quality sample or HD pictures at hand. Questions need to be thorough, since the diagnosis will result from the process of elimination. First, identify the turfgrass that has the problem. It is important to know the turfgrass species because certain species are susceptible to certain problems. A common problem I see each summer is rough bluegrass (Poa trivialis) going dormant under heat stress and it is sometimes misdiagnosed as a disease because the symptoms are similar in nature. Addi- tionally, warm-season grasses and summer annual weedy grasses like crabgrass, bermudagrass and prostrate knotweed go dormant or die in the fall and result in brown turf. Turfgrasses that are brown and straw-colored in the spring may be species that have a long winter dor- mancy. This is especially true for some Kentucky blue- grass cultivars. Certain turfgrasses are also susceptible to certain diseases, e.g., a common summer disease of tall fescue is brown patch. Kentucky bluegrass is sus- ceptible to summer patch and leaf spot, and perennial ryegrass is a host to most of the common diseases. Online prediction models have been developed that forecast when environmental conditions are right for a disease to occur. These prediction mod- els are based predominantly on local weather data, namely temperature and humidity. For example, brown patch disease is most severe when the sum of the daytime and nighttime temperature exceeds 150, with 10 hours of continuous leaf wetness. If those conditions exist and tall fescue cultivars are particu- larly susceptible to the disease, then there is a high probability that brown patch disease will occur. It is much easier to identify the fungal pathogen by the "symptom" it causes rather than the sign. Symptoms of the disease include leaf spots, blight, root rot, leaf tissue collapse and/or death. From a distance these symptoms will look like patches or mottled areas of discolored turf. They are generally circular in nature and typically do not spread in straight lines or blocks, however, when I stated as much at a conference an attendee later sent me a picture of Pythium on a golf green, spread by the mower and in perfectly straight lines. Examples of disease symptoms: Hourglass shaped lesions on leaves caused by dollar spot disease. Discolored spots on leaves and leaf twisting caused by grey leaf spot disease. Circular patches of brown grass caused by brown patch disease. Frogeyes, arcs and rings caused by summer patch, necrotic ring spot or fairy rings. Some of the symptoms are best-viewed close-up, possibly with a hand held magnifying glass, and some look more obvious from a distance. Some have unique symptoms, like the blue smoke ring seen around a brown patch of grass in the early morning (brown patch disease) or the obvious "frog-eye" of summer patch disease. Each of the diseases has a unique sign and symptom that help to identify it from the oth- ers. Signs are defi ned as a visual identifi cation of the pathogen, and include mushrooms, orange pustules, hyphae and/or mycelium. Signs are usually best seen fi rst thing in the morning, before the dew has burnt off. If there are no visible signs and symptoms are dif- fi cult to diagnose, it is best to send a sample away to a diagnostic lab. Check to see if your local Extension service or university turf program has one. In addition to disease, turfgrasses are susceptible to certain insects. For example, Kentucky bluegrass can be infested with bluegrass billbugs while peren- nial ryegrass will not. If the turfgrass species and time of year are ideal for white grub, billbug, or chinch bug (lawns primarily) damage, inspection of the soil and turf crown/roots will also help the identifi cation process. There are some good videos online showing how to perform the tug-test for bluegrass billbugs or sample for white grubs. Fields with a history of insect problems are likely to have repeat infestations, so it is important to keep good records. There are other turf problems that are not con- sidered biotic (living). These are referred to as abiotic problems. If the grass is chlorotic (yellow-brown) it could be soil-related. Is the soil saturated or compacted? Grasses cannot take up nutrients in waterlogged, poor soils. Has a soil test identifi ed any nutrient defi ciencies? Is the turf drought or heat-stressed? In some instances, poor irrigation distribution uniformity is the cause but those symptoms/patterns cannot be identifi ed clearly until you are standing up high, in the bleachers or stands. Other abiotic problems include blunt mower blade damage (notably on perennial ryegrass fi elds in spring when the turf is trying to go to seed), winter desiccation, traffi c damage during frost, fertilizer spills or chemical misapplications, an object sat on the grass for a prolonged period of time, or urine spots. Some of these abiotic problems are harder to diagnose so it is important to eliminate disease and insect issues from the onset. /ST/ www.spor tsturfonline.com 50 // August 2017 Q&A with PAMELA SHERRATT Sports Turf Extension Specialist Questions? Send them to Pamela Sherratt at 202 Kottman Hall, 2001 Coffey Road, Columbus, OH 43210 or sherratt.1@osu.edu Or, send your question to Grady Miller at North Carolina State University, Box 7620, Raleigh, NC 27695-7620, or email grady_miller@ncsu.edu Q: WHY IS MY GRASS BROWN?

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