A combination of raised mowing heights and lightweight rolling could help superintendents in their battle against anthracnose in annual bluegrass putting surfaces.
A study by researchers at Rutgers University showed that raising mowing heights by increments as little as 0.4 mm coupled with lightweight rolling every other day can help lessen the threat of anthracnose without compromising ball roll distance.
Results of the study, conducted in the summers of 2004 and 2005 by John Inguagiato, James Murphy, Ph.D., and Bruce Clarke, Ph.D., were published in the July-August edition of Crop Science.
Researchers mowed anthracnose-inoculated plots at three settings, 2.8 mm (0.110 inches), 3.2 mm (0.125 inches) and 3.6 mm (0.141 inches) with a John Deere 220B seven days per week and 14 times per week from June through August in both years of the study. The research showed that mowing at 2.8 mm increased severity of anthracnose by 3 percent to 21 percent compared with mowing at 3.6 mm and by 1.6 percent to 8 percent compared with mowing at 3.2 mm.
The Rutgers University study showed that raising mowing heights by increments as little as 0.4 mm coupled with lightweight rolling every other day can help lessen the threat of anthracnose without compromising ball roll distance.
The objective of the trial, researchers wrote, was to determine the effects of mowing height, mowing frequency and lightweight rolling, and their interactions with each other on severity of anthracnose, ball roll distance and turf quality on Poa annua putting surfaces.
Their study was conducted from June through August on newly established annual bluegrass plots in North Brunswick, N.J. Applications of fertilizer and plant growth regulators were made throughout the study to simulate actual golf course management practices. Diseases other than anthracnose and insect pests were controlled throughout the study, and anthracnose was controlled with chlorothalonil between study periods to allow the plots to recover.
Data showed that mowing height had the most effect on anthracnose severity.
Mowing at 2.8 mm increased anthracnose severity 3 percent to 17 percent in the first year of the study compared with mowing at 3.6 mm and 13 percent to 21 percent in year two. Mowing at the lower height also increased disease severity 1 percent to 8 percent in both years of the study, compared with mowing at 3.2 mm.
Contrary to what researchers had anticipated, increased mowing frequency did not lead to increased incidence and severity of anthracnose, and on occasion actually resulted in reduced disease severity.
Mowing 14 times per week at 3.6 mm and 3.2 mm resulted in reduced disease severity compared with mowing at 2.8 mm, but there was little or no difference between mowing heights when the plots were mowed seven days per week.
Mowing height also had the greatest affect on ball roll distance. Mowing at 2.8 mm resulted in increased ball roll distance of 0.2 meters to 0.4 meters compared with mowing heights of 3.6 mm.
Lightweight greens rolling, compared with no rolling affected ball roll distance only slightly. Likewise, rolling every other day reduced anthracnose severity only slightly in both years of the study, ranging from 1 percent to 6 percent compared with the control (no rolling).
Increased ball roll distance in the Rutgers study was less than what had previously been reported in trials conducted on bentgrass greens by Thom Nikolai, Ph.D., at Michigan State in 2004.
Researchers concluded that increased mowing height can reduce severity of anthracnose in Poa annua greens by as much as 11 percent. They also learned that mowing twice per day at higher heights of cut was nearly as effective as mowing at 2.8 mm at inducing maximize ball roll distance. Therefore, the research showed that anthracnose severity can be reduced by raising mowing heights to 3.2 mm or 3.6 mm and increasing mowing frequency and lightweight greens rolling.
Most importantly, researchers noted that any regimen of cultural management practices designed to help control anthracnose should complement a fungicide management program, not replace one.
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