Plant health and yield of dry bean not affected by strobilurin fungicides under disease-free or simulated hail conditions

Strobilurin fungicides have been advocated to manage plant stress, optimize plant health, and increase yields of several crops. Studies were conducted in 2006, 2007, 2008, and 2009 to determine if azoxystrobin or pyraclostrobin induced plant health effects and increased yield of dry bean grown under conditions with very low levels of foliar disease and with the application of a simulated hail stress treatment. Azoxystrobin (125 g a.i. ha(-1)) and pyraclostrobin (100 g a.i. ha(-1)) applied at the start of flowering reduced the percentage of harvested dry bean seeds that were discoloured or misshaped (i.e., pick value) to 2.06 and 2.15%, respectively compared with 2.4% for the untreated control. Increased seed quality of edible legumes has been identified as a plant health benefit induced by strobilurin fungicides; however, neither fungicide contributed to increased seed weight or dry bean yield compared with the untreated control in the presence or absence of a simulated hail treatment. The results of this study suggest that the application of azoxystrobin or pyraclostrobin when dry bean growing conditions are unfavourable for disease development should be weighed against economic considerations and the potential risks associated with disease resistance development.