Novel Spring Dead Spot Control Using Isofetamid.

Bermudagrass is one of the most utilized species worldwide for intensive turfgrass systems in tropical and subtropical regions. This grass is often utilized beyond the primary zone of adaptation because of a favorable growth habit. The most prominent challenge is the management of spring dead spot (SDS). Many turfgrass managers apply fungicides during the fall to suppress symptom expression in the spring, though efficacy is often inconsistent with available chemistries. The objective of this research was to evaluate isofetamid for suppression of SDS on hybrid bermudagrass (HBG) putting greens and fairways. Trials were established on a ‘MiniVerde’ ultradwarf putting green in 2015-2017 and on a ‘Vamont’ HGB fairway in 2016-2017. Treatments were applied in the fall at soil temperatures of 18°C. Isofetamid provided complete control of SDS on putting green turf in each year with a single application of 4.3 kg ai ha^-1 and a split application of 2.5 kg ai ha^-1 followed by 1.8 kg ai ha^-1 on a 28-day interval. In comparison, penthiopyrad (1.1 kg ai ha-1), did not significantly reduce spring dead spot incidence or severity in 2016 or 2017. Isofetamid was evaluated on a fairway at rates of 0.63 kg ai ha^-1, 1.27 kg ai ha^-1, and 1.91 kg ai ha^-1 applied twice, 2.54 kg ai ha^-1 followed by 1.80 kg ai ha^-1, and a single application at 4.34 kg ai ha^-1. Percent diseased area was reduced with multiple applications at rates of 1.27 kg ai ha-1 and above, but not at 0.63 kg ai ha^-1 or the single application at 4.34 kg ai ha^-1. The severity of SDS was reduced by all treatments except the lowest tested rate. Tebuconazole at 1.51 kg ai ha^-1 did not reduce disease incidence or severity in this study. These data suggest that isofetamid is a viable option for controlling SDS on bermudagrass greens and fairways, though more research is needed to determine optimal use rates for each grass.