Impact of Fraze Mowing on Spring Dead Spot Severity.

Fraze Mowing Impact on Spring Dead Spot Severity

Spring dead spot, caused by Ophiosphaerella spp., is the most important disease of bermudagrass (Cynodon dactylon) and its hybrids (C. dactylon × transvaalensis) in regions where cold temperatures induce dormancy. Control of the disease is difficult, often requiring multiple fungicide applications over multiple years to achieve satisfactory control.  Recently, the practice of "fraze mowing" has been utilized to remove surface organic material on bermudagrass athletic fields, with the aimed benefit of removing weeds and producing a smoother playing surface. This ongoing study investigates the impact of fraze mowing a 'Riviera' bermudagrass site with severe spring dead spot caused by O. herpotricha. Plots were 1.5 m × 3 m and arranged in a randomized complete block design with four replications. Treatments were arranged in a split plot design with fraze mowing as the main plot and nitrogen source as the subplot. Fraze mowing was conducted on 22 July 2014 at four and eight mm with a Koro Field Topmaker¨ or not cultivated. Ammonium sulfate or urea was applied weekly at 24.4 kg N ha^-1 for six weeks after fraze mowing. Area under the green cover curve (AUGGC) and area under the disease progress curve (AUDPC) were calculated based on digital image analysis and visual estimation of spring dead spot severity recorded every 14 d in spring 2015.  All data were subjected to analysis of variance, and means were separated with single pair-wise orthogonal contrasts.  Fraze mowing at four mm or eight mm increased AUGGC values compared to no fraze mowing, but did not reduce AUDPC values.  No difference was observed among nitrogen source treatments. Over a single season of study, fraze mowing alone did not substantially reduce an established spring dead spot epidemic, but may be a portion of an overall integrated control strategy.