As we roar into fall with highs still in the mid 80s, longer nights and less daylight add up to increased opportunity for disease. Combine that with just a little added stress from verticutting and Curvularia will gladly jump all over a green. Curvularia may not cause severe damage, but is still very unsightly to say the least. Cleary Chemical Corporation offers two effective combination products, Spectro 90 and 26/36, which will quickly take out Curvularia.
The greater threat of late is ETRI, or ectotrophic fungi, better known as Bermuda Decline or Take-all patch. In Florida, many areas are faced with higher salt levels due to lack of rainfall and hot days. With more winds from high and low pressure areas meeting over Florida and drying out greens, root systems are being put to the test. As these fungi are always present in the soil, it is up to the turf or a consistent preventative program of 3336 to defeat them. This disease has been known as Gaeumannomyces, Ophiobolus, Leptosphaeria, Othiosphaerella, Phialophora and Magnaporthe spp., and as we tend to keep simplifying things, it has become ETRI, but regardless of what it is called, it still can’t hide from 3336.
Curvularia blight is normally a weak pathogen, but when the turf is stressed and the weather is warm and wet, it can noticeably affect many warm season grasses including bermudagrass, zoysiagrass, and centipedegrass. Symptoms usually include leaf spotting and yellowing of turf in small patches. Under severe conditions, the disease can cause death of entire leaves and tillers and can result in a thinning of the turf. Cultural control options include reducing spring nitrogen applications, proper water management, and verticutting when conditions are less favorable to the disease. The use of curative fungicides will help avoid the spread of Curvularia spp. Where repeated rainfall occurs the shortest re-treatment interval is recommended for maximum control.
Bermudagrass decline of bermudagrass (Take-all patch of St. Augustinegrass) is caused by the fungus Gaeumannomyces graminis. This root-infecting fungus occurs on weakened or damaged turf. The fungus is active in the fall when there is adequate moisture in the soil but damage symptoms, which include turf yellowing in patches, are most evident in the spring and summer. The turf may eventually be killed in these patches. Regrowth into this area is usually very slow. Rotting of roots occurs and brown hyphal runners may be seen on the root surface. Cultural control requires following proper management practices to reduce predisposing turf areas to this disease. Raising the mowing height, if at all possible, seems to be the most effective step to reducing bermudagrass decline. Aerification to improve drainage and verticutting to remove thatch can also alleviate the symptoms. Because the disease is suspected to be active in the fall, preventative fungicide treatments should be used during the fall months to be most effective.
