ABSTRACT
Spring dead spot, caused by Ophiosphaerella spp., is the most important disease of bermudagrass (Cynodon dactylon and C. dactylon × C. transvaalensis) where cool temperatures induce dormancy. Field plot studies were conducted from 2004 to 2008 to determine the frequency and timings of fungicide applications for control of the disease. The fungicide treatments included tebuconazole applied two, three, or four times in the fall, once in the spring plus twice in the fall, or twice in the spring and twice in the fall. Propiconazole treatments consisted of one spring, one spring and one fall, one spring and two fall, or two fall applications. Disease severity in plots treated three or four times in the fall with tebuconazole was significantly lower than for those not treated. Based on the change in patch size prior to treatment, patches in plots treated four times with tebuconazole were smaller than in the previous year and were smaller than patches treated once in the spring and twice in the fall or twice in the fall. Plots receiving two fall, one spring and one fall, or one spring and two fall applications of propiconazole had less disease than plots treated once in the spring or plots not treated. Based on the change in plot area prior to treatment, plots receiving two fall, one spring and one fall, or one spring and two fall propiconazole applications had a reduction in plot area expressing symptoms of disease. These studies demonstrated that two fall or one spring and one fall application appear to provide the most effective and cost effective disease control in an integrated approach to managing the disease. The study also demonstrates the importance of disease severity assessment prior to treatment in evaluating the efficacy of a control measure for spring dead spot.
