Evaluation of Strobilurin Fungicide Applications for Plant Health Benefits.

Strobilurin fungicides represent one of the largest classes of fungicides used in crop protection in the United States.  Recently, secondary effects of strobilurin fungicides have been observed in crops with a promotion of plant health when disease is not visibly present. Applications of strobilurin fungicides have increased stress tolerance and yield in crops such as corn and wheat in absence of visible disease. Research has shown enhanced anti-oxidant activity in leaves and a partial inhibition of the plant hormone ethylene increasing photosynthetic activity of older leaves treated with strobilurin fungicides. In turf, applications of pyraclostrobin increased root length and density in creeping bentgrass (Agrostis stolonifera L.)under greenhouse conditions.  In this experiment, azoxystrobin, pyraclostrobin, fluoxastrobin, and trifloxystrobin were applied bi-weekly to a simulated creeping bentgrass putting green in absence of disease.  Experimental units were arranged in a split-plot randomized complete block design; whole plots were treated with iprodione and chlorothalonil or left untreated to control foliar diseases for the duration of the experiment to ensure disease free assessments.  Aboveground plant health was assessed using Normalized Differential Vegetation Index. Percent turf cover was evaluated using digital image analysis. Canopy temperatures were measured with an infrared camera prior to each application. Below ground plant health was determined by a root assessment using WinRHIZO image analysis system at the termination of the trial period to record root architecture and biomass through destructive sampling.