Use of Remote Sensing and Geospatial Mapping to Measure Plant Response to Two Demethylation Inhibiting Fungicides.

Demethylation inhibiting fungicides (DMI) and plant growth regulators are both commonly used chemistries to manage annual bluegrass (Poa annua L.) on golf putting greens. Most active ingredients within the DMI group have a broad scope of pathogen inhibition, however, there is concern about growth regulation and/or phytotoxicity associated with their use in turf. This concern is amplified when the products are used in conjunction with certain growth regulators. Trinexapac-ethyl (TE) (Primo Maxx, Syngenta) reduces turf growth and improves stress tolerance by reducing cell elongation. A study was established to evaluate the interaction of TE rotated with two common DMI fungicides; propiconazole (Banner Maxx, Syngenta) and triticonazole (Chipco Triton Flo with StressGard™ Formulation Technology, Bayer ES). Three trials were established on an existing golf practice putting green at Hanging Rock Golf Course in Salem, VA in 2010 with start dates in June, July, and August. Replications were arranged by anticipated foot traffic stress. Multispectral radiometry was used to measure turf stress throughout the summer. A Crop Circle ACS-210 (Holland Scientific LLC, Lincoln NE) was used to collect reflectance information in the red and near-infrared spectral regions and data were used for two vegetative indices; normalized difference vegetative index (NDVI) and ratio vegetative index (RVI). Geospatial information were collected with a decimeter global positioning unit (AgGPS 432 Receiver, Trimble Navigation Limited, Sunnyvale CA) and uploaded to a web-based data processing service (TurfScout LLC, Tifton GA). Additional data collected included visual turf quality (1 to 9 scale, with 9 being highest), percentage dollar spot and anthracnose, and visual turf phytotoxicity. Results indicated that alternation with TE prior to stress improves season-long turf quality but may be too injurious when initiated during heat stress. Long-term, triticonazole treated plots exhibited greater plant health than those treated with propiconazole. Based on reflectance and visual estimates, TE consistently enhanced the performance of propiconazole, whereas impact was minimal to negative in conjunction with triticonazole. Greatest turf improvement with triticonazole occurred approximately one month and beyond after initial application for each trial. Quality of propiconazole treated plots was highest initially but declined following subsequent applications.