April showers bring May flowers and fungus, too

By By Steve Strong / area horticulture extension agent
April 30, 2003
The past month has gifted East Central Mississippi with more than its share of April showers. Local weather experts report in excess of 10 inches of rainfall for the month, nearly 5 extra inches above average, and that's not counting the extra foot of water that fell in February.
All that abundant moisture, combined with cool night temperatures and high daytime humidity, has created perfect growing conditions for disease-causing fungi.
Powdery mildew, anthracnose, and botrytis all began an early attack on dogwoods and roses this spring, joined by a gang of others making up the "10 Least Wanted List" in the landscape.
Brown patch fungus on turf grass tops the list, causing homeowners more headaches than all other problems combined. Even if you don't grow flowers or vegetables, almost everybody has a small patch of grass to wiggle their toes in. And of all things, turf should be easy to grow, right?
Under normal conditions the answer is yes, but around here the weather patterns are anything but normal. Temperatures in our region can vary as much as 40-50 degrees in a single day, and that kind of extreme change is pretty hard on young turf just growing out of winter dormancy.
Brown patch fungus (Rhizoctonia solani) thrives during both spring and fall growing seasons, at times when the turf is most vulnerable.
Brown patch can attack most any grass species, however, Centipede, St. Augustine, and common Bermuda are where the damage is usually seen.
Irregular shaped, circular spots begin to form in the turf and can vary in size from a few inches to several feet in diameter. The affected areas take on a brown or grayish color, sometimes bordered by a darker smoke-colored ring. Leaves often turn yellow before dying on St. Augustine, and sometimes to a reddish color on centipede turf.
If not controlled in the early stages, brown patch and several other turf diseases can invade turf roots and kill large areas of the lawn. Repeated applications of approved turf fungicides can help protect the grass until hotter, drier weather naturally causes brown patch activity to decrease.
There are several factors that tend to make grass more susceptible to brown patch and many other turf pathogens. Excessive applications of nitrogen fertilizer are probably the most common cause, as homeowners often try to feed the grass too early in the season, before it is able to absorb the nutrients.
Along with waiting as late as May to fertilize the lawn, another good strategy to prevent fungal outbreak is watering only during the morning hours. Irrigation late in the day or in the evening hours causes the turf leaves to stay wet for longer periods, creating the moist conditions for disease growth.
Thatch buildup is also a disease promoter, and periodic raking or de-thatching reduces the amount of decayed organic matter where turf diseases thrive. Be sure to use the correct mowing height for your specific turf grass to minimize thatch buildup, and keep the mower blade sharp for each cutting to prevent additional turf damage.
Contact your county Extension office for more information on fungicide use, disease analysis and fertilizer and soil testing recommendations.
Visit the MSU Web site at www.msucares.com for free publications on lawn care and pest management strategies.