Agri Leader

Watch out for lawn disease during the wet season

RODOLFO ROMAN
Published: August 22, 2012

Unlike the rest of the country, which has been a victim of a dry spell, South Florida is on the opposite side of the situation.

The region has received lots of rain this year, considering the season began earlier than normal.

From April through July, the amount of rainfall increased well above normal numbers for each month. During that time, it totaled approximately 20 inches, based on Miami airport records.

Home gardening adviser John McLaughlin suggested refraining from irrigation to prevent grass issues.

He recommended keeping an eye on the weather in regards to rain. If there is none for more than three days, then turn on irrigation just before sunrise if there isn't rain in the forecast, he said.

"Soil that remains excessively moist promotes root diseases, while leaf spotting diseases are more likely where grass blades remain wet," he said. "In both Miami-Dade and Broward, various cultivars of St. Augustine grass are by far the most frequently used for residential lawns, so the following comments are with that fact in mind. However, all types of turf grass are more prone to disease if soil and plant surfaces remain wet for an extended period."

If there is poor drainage, soil is likely to remain wet.

"One alternative if there is a spot in your yard that remains wet is to consider alternatives to turf, such as a shrub that can survive in such conditions," he said.

Organic matter soil can retain moisture. So, when laying turf on limestone, use no more than a 1-inch thick layer of 50-50 sand/black topsoil. However, don't lay any new turf on top of old or dead turf because it will impede root penetration into the soil, and the old turf will rot.

More than likely, there will be damage in the area where there is shade, causing grass to remain wet for a longer period because of the lack of sun. This can increase the chances of disease like fungal leaf spotting. Applications of nitrogen and potassium can help fight the disease.

Maintenance before the rainy season can determine vulnerability.

"Turf that is drought stressed during spring is at greater risk of disease during the rainy season, especially take-all root, which rots roots and stolons," he said. "Once disease symptoms are first noted, treatment using fungicides is not very effective. If you have had problems with take-all root, consider an application of a lawn fungicide before the start of rainy season and then at monthly intervals until rainy season ends."

Consult the county extension office or the University of Florida Plant Disease Clinic to diagnose a disease.