Monday, November 5, 2007
75-3
Mechanical Injury and Yellow Spot Severity In Bentgrass As Influenced By Fungicides.
Summer bentgrass decline generally is due to a combination of biotic and abiotic stress factors. Previous studies have shown that some fungicides can improve summer quality of creeping bentgrass (Agrostis stolonifera L.; CBG) in the absence of disease. This two year field study primarily focused on chlorothalonil (CHLOR), fosetyl aluminium (FA), pigmented mancozeb (P-MAN) and potassium salts of phosphorous acid (K-P) and tank-mix combinations applied on 14-day intervals to ‘Declaration’ CBG between early June and early August in 2006 and 2007. In 2007, a non-pigmented formulation of MAN was compared to P-MAN. All fungicide combinations could not be assessed due to space restrictions. The study site was maintained under putting green conditions and was inadvertently scalped in both years and turf quality ratings were used as a measure of injury level. In 2006, yellow spot (cyanobacteria proposed as incitants) uniformly affected the area, and in 2007 the site was vertical cut in late July to provide more injury assessment. In both years, plots treated with FA + CHLOR or K-P + P-MAN sustained less injury from scalping. Treatments containing CHLOR were most effective in controlling yellow spot, but P-MAN also suppressed the disease in 2006. Treatments containing P-MAN and MAN reduced injury from vertical cutting in 2007. The mechanism(s) by which fungicides reduce mechanical injury in CBG is unknown.
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