Use of a Soil Surfactant with Fungicides for Control of Fairy Ring Disease in Turfgrass

Fairy ring is the common name for a complex disease of turf encompassing the appearance of mushrooms, circles of stimulated grass, or rings of damaged or dead turfgrass maintained for lawns, athletic fields, or golf courses. Type-I fairy ring is especially destructive due to the development of water repellent or hydrophobic soil conditions and the subsequent decline and damage to the existing turfgrass. Fairy ring management strategies, particularly the control or suppression of Type-I fairy ring symptoms, has been inconsistent in effectiveness. The objective of this field study was to evaluate the efficacy of fungicides recommended for fairy ring control when applied alone and with a soil surfactant. This research was conducted on cool-season turfgrass in California in 2005, and in Pennsylvania in 2006. The same treatments were applied at both locations. The four fungicide treatments were evaluated at 620 g active ingredient (a.i.) azoxystrobin∙ha⁻¹, 9757 g a.i. flutolanil∙ha⁻¹, 310 g a.i polyoxin-D∙ha⁻¹, or 558 g a.i. pyraclostrobin∙ha⁻¹. Each fungicide was applied alone and in a tank-mix combination with the modified alkylated polyol soil surfactant (100 % concentration) at 19 L product∙ha⁻¹. All treatments were applied at two water carrier volumes of 814 and 1628∙ L∙ha⁻¹. At both locations, Type-I fairy ring symptoms were noticeably reduced in plots treated with fungicides plus soil surfactant at either water carrier volume versus plots treated with fungicides alone applied at 814 L water carrier ha⁻¹. Therefore, the consistently best overall treatment for the control or suppression of Type-I fairy ring symptoms was fungicides plus soil surfactant at either water carrier volume. The application of plant protection products at the lower water volume is preferred by turfgrass managers and practitioners; thus the utility of soil surfactants applied with fungicides is a useful strategy for the chemical control of fairy ring in turf.