Effect of microwave radiation on dry bean seed infected with Colletotrichum lindemuthianum with and without the use of chemical seed treatment

Abstract

Seed-borne anthracnose, caused by Colletotrichum lindemuthianum, is a serious disease that affects dry bean (Phaseolus vulgaris L.) seed quality and yield. A 2-yr study was conducted to examine the effect of microwave radiation on two bean cultivars, Navigator (navy bean) and AC Ole (pinto bean). In the laboratory, a maximum exposure time between 40-50 s caused < 10% decrease in seed germination and 0.14 and 0.10% s-1 decrease in pathogen viability for the Navigator and AC Ole cultivars, respectively. Field studies were conducted at Ridgetown and Exeter, ON, to evaluate the effect of microwave radiation and two chemical seed treatments (thiamethoxam+fludioxonil+metalaxyl-M+azoxystrobin and pyraclostrobin+fluxapyroxad+metalaxyl), on emergence, percentage of infection, seed pick, yield and return on investment. Microwave treatment decreased emergence by < 10% in both cultivars and decreased disease symptoms by 17-23% for leaf and stem infection in cv. AC Ole when combined with chemical seed treatment. Microwave treatment did not affect pod infection, seed pick, yield, or return on investment, yet chemical treatment increased yield between 9 and 25% in cv. Navigator.