Update from Uconn Turfgrass Pathologist
Its been a very difficult summer for turfgrass managers. The below communication is from Dr. Inguagiato from UCONN
Stresses Turfgrasses routinely are negatively affected by stressful summer conditions. Stresses generally include turfgrass disease (biotic stress) as well as physiological decline associated with environmental effects on turfgrass health (abiotic stress). Superintendents and their staff implement management practices before and during summer stress to minimize detrimental effects and help turf survive. However, the above average heat, humidity, and rainfall affecting much of CT this July and August have exceeded the capacity of turfgrasses to cope with these stresses despite implementing best management practices to sustain summer turfgrass performance.
Healthy turfgrasses produce more energy (i.e., photosynthesize) than they consume (i.e., respire). When consumption exceeds production turfgrass health declines. This balance of supply and demand is largely dictated by soil temperature. When soil temperatures reach 70˚F, demand begins to equal or surpass supply. Due to the high nighttime temperatures this year, the average soil temperature during mid-July to mid-August has been 77˚F (2 in. depth) in Storrs, CT. These excessive soil temperatures result in a failure of turfgrasses to produce enough energy to maintain healthy growth. This is particularly evident in putting green turf, where low mowing heights reduce the amount of green leaf tissue available for energy production through photosynthesis.
Soil moisture also impacts turfgrass root health. Prolonged saturated rootzones cause root decline. A healthy soil rootzone contains approximately 25% airspace to provide roots the oxygen necessary to function. This year, root health and putting green firmness have been affected at golf courses throughout CT by excessive rainfall during July and August. Over 10 inches of rain has been recorded since July in Storrs, CT. Hartford received over 6 inches of rain during the first half of August alone, 3 times the 30-yr average. Putting greens built with sand rootzones are more capable of draining excessive rain, and maintaining good rootzone aeration, however turf grown on native soil greens is more likely struggle under current conditions. Furthermore, prolonged periods of high humidity reduce the ability of saturated putting surfaces to dry out.
This July and August have at many times felt like a steam-filled shower. Nighttime temperatures ≥ 65˚F and prolonged high humidity have been ideal for growth of fungal pathogens and development of various turfgrass diseases throughout the state. Results from UCONN turfgrass disease research trials and diagnoses from samples submitted to the UCONN Turfgrass Disease Diagnostic Center suggest this to be an above average year for disease severity. An increase in the occurrence of Pythium blight has been notable since July. Moreover, fungicides used to control this disease during most years have been less effective during exceptionally conducive disease conditions this year; requiring the use of more effective, and expensive fungicides to be used to prevent turf losses.
Anthracnose and dollar spot have also been particularly severe this year. UCONN research trials have shown fungicide efficacy against these diseases has also been reduced, in some cases resulting in unacceptable damage under increased disease pressure this year. Anthracnose control has only been achieved with fungicides considered “excellent” whereas “good” to “fair” products have failed to prevent the disease. Several fungicides that typically provide reliable 21-d dollar spot control all demonstrated disease breakthrough during favorable conditions in early-August.
By: John Inguagiato, Ph.D. UCONN
Stresses Turfgrasses routinely are negatively affected by stressful summer conditions. Stresses generally include turfgrass disease (biotic stress) as well as physiological decline associated with environmental effects on turfgrass health (abiotic stress). Superintendents and their staff implement management practices before and during summer stress to minimize detrimental effects and help turf survive. However, the above average heat, humidity, and rainfall affecting much of CT this July and August have exceeded the capacity of turfgrasses to cope with these stresses despite implementing best management practices to sustain summer turfgrass performance.
Healthy turfgrasses produce more energy (i.e., photosynthesize) than they consume (i.e., respire). When consumption exceeds production turfgrass health declines. This balance of supply and demand is largely dictated by soil temperature. When soil temperatures reach 70˚F, demand begins to equal or surpass supply. Due to the high nighttime temperatures this year, the average soil temperature during mid-July to mid-August has been 77˚F (2 in. depth) in Storrs, CT. These excessive soil temperatures result in a failure of turfgrasses to produce enough energy to maintain healthy growth. This is particularly evident in putting green turf, where low mowing heights reduce the amount of green leaf tissue available for energy production through photosynthesis.
Soil moisture also impacts turfgrass root health. Prolonged saturated rootzones cause root decline. A healthy soil rootzone contains approximately 25% airspace to provide roots the oxygen necessary to function. This year, root health and putting green firmness have been affected at golf courses throughout CT by excessive rainfall during July and August. Over 10 inches of rain has been recorded since July in Storrs, CT. Hartford received over 6 inches of rain during the first half of August alone, 3 times the 30-yr average. Putting greens built with sand rootzones are more capable of draining excessive rain, and maintaining good rootzone aeration, however turf grown on native soil greens is more likely struggle under current conditions. Furthermore, prolonged periods of high humidity reduce the ability of saturated putting surfaces to dry out.
This July and August have at many times felt like a steam-filled shower. Nighttime temperatures ≥ 65˚F and prolonged high humidity have been ideal for growth of fungal pathogens and development of various turfgrass diseases throughout the state. Results from UCONN turfgrass disease research trials and diagnoses from samples submitted to the UCONN Turfgrass Disease Diagnostic Center suggest this to be an above average year for disease severity. An increase in the occurrence of Pythium blight has been notable since July. Moreover, fungicides used to control this disease during most years have been less effective during exceptionally conducive disease conditions this year; requiring the use of more effective, and expensive fungicides to be used to prevent turf losses.
Anthracnose and dollar spot have also been particularly severe this year. UCONN research trials have shown fungicide efficacy against these diseases has also been reduced, in some cases resulting in unacceptable damage under increased disease pressure this year. Anthracnose control has only been achieved with fungicides considered “excellent” whereas “good” to “fair” products have failed to prevent the disease. Several fungicides that typically provide reliable 21-d dollar spot control all demonstrated disease breakthrough during favorable conditions in early-August.
By: John Inguagiato, Ph.D. UCONN
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