Many calls and samples come in this last week asking about yellow spots, plants, areas, patterns, etc., on turf. There are many reasons for this and no one cause seems to be involved with a majority of the cases. Historically there are more strange patterns and unusual symptoms of yellowing and uneven greening of turf in the early spring then at any other time of the year! The following are some factors to look for and consider.
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POA ANNUA. Poa annua spring green up, many different weather conditions, along with the genetic variability of this turf, lead to uneven green up and variable growth. The more annual types may be more vulnerable to winter kill/damage and leaf tip yellowing from fluctuating spring temperatures and frost. It would be advised to carefully examine the crowns of individual plants to see alive and healthy.
BASAL ROT ANTHRACNOES. This disease has been seen on at least one sample BUT was just one of several factors present. This is a problem from the past and not a disease that just started this year. It there was a problem with anthracnose last year it will over winter in infested plants and can invade weakened plants if predisposed by various stress factors. If present, aggressive management procedures should be initiated immediately. This would include both cultural practices and fungicide applications.
MULTICOLORED TURF, rapid fluctuating temperatures and wide swings in temperatures can result in many different colors of tissue. Such as a darkening of the turf leaves; yellowing; tip die back; reddening or purple leaf blades, leaf tips, leaf margins and seed heads; etc. The red or purple color is often associated with nutritional deficiencies but is more likely to be a temperature response at this time of year. Also due to cold soils fertilizer response on turf is slow. Frost on lush spring turf may result in strange color patterns. Genetic variability is often the reason why there are patches or circular patterns on off colored turf.
YELLOW TUFT/DOWNY MILDEW. Yellow Tuft/Downy Mildew has been suspected on several greens. To date there have been no confirmed cases of this disease. Overall symptoms may mimic textbook illustrations of yellow tuft but it is really too early for its development. If the distinct clumping of meristematic tissue cannot be found consider other factors.
FUSARIUM PATCH/PINK SNOW MOLD. This disease can rapidly become active and cause yellowing of turf, especially Poa annua, during cool wet conditions. Just last weekend, April 2, much of Ohio had abundant rain and snow. Often damage is short term. Samples with this disease are usually confirmed all the way until June, in Ohio.
The author is a professor of plant pathology at The Ohio State University, Columbus, Ohio.
