Sensitivity of Mycosphaerella pinodes to pyraclostrobin and optimizing fungicide application in field pea

Abstract

Mycosphaerella pinodes caused by mycosphaerella blight, a destructive disease of field pea is primarily managed with foliar fungicides. Development of fungicide insensitivity in M. pinodes could severely reduce management options. The objectives of this study were to assess insensitivity to pyraclostrobin fungicide in M. pinodes populations from western Canada and the U.S.A., and to determine the optimum fungicide delivery system to manage mycosphaerella blight. Over 300 M. pinodes isolates collected in 2010-11 were tested for insensitivity and 19 isolates were found to be insensitive to the fungicide, suggesting the need for judicious use of pyraclostrobin. Sprayer technology trials under field conditions revealed that double nozzles and water volumes up to 400 L ha-1 improved fungicide efficacy relative to control treatments. Above 400 L ha-1, disease was higher and yield was lower in all trials, suggesting that higher volumes can over-saturate the leaves and cause fungicide run-off.