POTENTIAL OF AN ORGANOSILICONE SURFACTANT TO IMPROVE SOIL WETTABILITYAND AMELIORATE FAIRY RING SYMPTOMS CAUSED BY MARASMIUS-OREADES

Currently, chemical control of fairy ring caused by Marasmius oreades is not feasible, in part because colonized soil is very repellent to p esticidal solutions. Fungicidal control, however, might be successful if a surfactant was used to increase soil wettability. Of 13 surfactan ts screened for ability to enhance solution uptake by infested soil co res, the organosilicone, Silwet L-77, was most effective, followed by Citowett Plus and Agsurf. In a second, similar experiment, Silwet L-77 was more effective than the other two surfactants in increasing water uptake by both infested and uninfested soil cores. Silwet L-77 concen trations of 0.98-3% were equally effective in increasing grass product ion, relative to the water control, on colonized and uncolonized turf, under greenhouse conditions. At concentrations of 2 % or higher, but not at concentrations of 0.016% to 1.0%, Silwet L-77, Citowett Plus, a nd Agsurf prevented M. oreades growth in liquid culture. Silwet L-77, and perhaps other organosilicone surfactants, seemingly have considera ble potential for the management of fairy ring by improving uptake of water, or as carriers of biological or chemical control agents.