With the return of cool, rainy weather to much of the state, what can we expect as far as turf diseases? The good news is that dollar spot, which began to show up across the state, will likely go into a state of remission. However, two cool-weather diseases, red thread and Fusarium patch, may be reactivated and make another appearance--temporarily.
Of the two diseases, red thread is more likely to reappear during this cool, wet spell. This disease is particularly common in fine-leaf fescues and perennial ryegrass and is favored by cool (60 to 75 degrees F), wet periods coupled with extended overcast conditions in spring and fall. From a distance, you will notice patchy areas ranging in diameter from a few inches to a couple of feet. These patches will have an unhealthy tan to pinkish cast to them. When you can get a closer look at the turf, the signs of red thread should be quite distinctive. If the turf is wet from dew or rain, you will see pink to reddish gelatinous fungal growth emerging from the leaves and sheaths. As the disease progresses and more of the turf turns dry and tan, the pinkish fungal growth stands out even more and begins to look like red threads. These threads drop into the thatch, allowing the pathogen to survive for long periods. Red thread is generally, but not always, most common on under-fertilized turf. Cultural control measures include
- maintaining adequate, balanced fertility
- mowing frequently and collecting the clippings (and threads)
- decreasing the amount of shade
- increasing air circulation to enhance drying of turf
In cases where such measures are not adequate, chemical controls may be justified. Chemicals labeled for use in Illinois are listed in the Illinois Commercial Landscape and Turfgrass Pest Management Handbook, 1998-1999 (page 13). For more information, consult Report on Plant Diseases No. 413.
Turfgrass specialist Dr. Tom Voigt reminds us that Fusarium patch (called pink snow mold when snow is present) was active through May this year--but was active into early June last year. This disease affects a wide range of turfgrass species and is favored by prolonged periods of cool (60 degrees F), wet, overcast weather. Symptoms of patch diseases vary, depending on the height of the turf. On lawn-type turf, small, water-soaked patches two to three inches in diameter will appear and rapidly change to a reddish brown color. Cultural control measures (for this time of year) include decreasing shade and increasing air circulation to enhance drying of turf. Preventive fungicide applications are probably not warranted because warmer, drier conditions are sure to return soon (we hope!). For more information, consult Report on Plant Diseases No. 404.