Nitrogen Source and Fungicide Interaction Efficacy On Sclerotinia Homoeocarpa Causal Agent of Dollar Spot On Creeping Bentgrass Agrostis Stolonifera L. Var Palustris Huds.

Dollar spot S. homoeocarpa is one of the most destructive diseases turf managers face annually. Warm and cool season grasses throughout the world are susceptible to S. homoeocarpa. The purpose of this study was to evaluate the interaction between nitrogen source and fungicide efficacy on S. homoeocarpa. Evaluation began on May 12, 2010. Grasses evaluated were Agrostis stolonifera L. var palustris (Huds.) cultivar Crenshaw. Products being evaluated were: Daconil ultrex (Chlorothalonil), Headway (Azoxystrobin + Propiconazole), Rhapsody (Bacillus subtilis QST 713), EcoGuard (Bacillus licheniformis SB3086), Paradigm (Clove oil, Wintergreen oil, and Rosemary oil) and Regalia (Reynoutria sachalinensis). Applications of fungicide programs were made every 14 days.

 Nitrogen was applied at 4 pounds per 1000 ft² annually. Three nitrogen sources were used, 41-0-0 Polyon slow release granular, 21-0-0 ammonium sulfate quick release granular and 30-0-0 liquid nitrogen. Additional phosphorus and potash applied through separate products to provide a 1-1-2 ratio of N-P-K.

 This project was a split plot design, 9 fungicide treatments were evaluated on the main effect of nitrogen source. Test plots measured 1.0 meters by 1.0 meters. Disease incidence and quality ratings were taken weekly and averaged for each month. LSD was calculated using Fisher’s LSD, alpha 0.05. Area under disease progress curves (AUDPC) were calculated based on disease incidence ratings. Repeat treatments and additional screening of products will be continued for timing, rates and control of S. homoeocarpa.