Selection of effective fungicides against Botrytis cinerea from tomato in Nara Prefecture by sensitivity test

Abstract

In 2021, 83 isolates of Botrytis cinerea Pers. were collected from tomato fields in Nara Prefecture, Japan, and their sensitivity to fungicides was evaluated. The rates of isolates resistant to diethofencarb, penthiopyrad, thiophanate-methyl, and azoxystrobin were high and equalled 96.3%, 92.8%, 79.5%, and 46.3%, respectively. In contrast, the rates of isolates resistant to iprodione were low, amounting to 20.5%. No isolate resistant to mepanipyrim was detected. Only 4.1% of the isolates exhibited low sensitivity to fenhexamid. Tomato farmers in Nara Prefecture frequently used diethofencarb, penthiopyrad, thiophanate-methyl, and azoxystrobin though the resistance to those fungicides was observed in over 30% of the isolates. Our results suggested that mepanipyrim and fenhexamid could be effective fungicides. It was essential to identify effective fungicides via sensitivity experiments, to control Botrytis cinerea in production fields because of the frequent occurrence of isolates resistant to multiple fungicides.