Efficacy of fungicides in controlling Botrytis cinerea

We evaluated the curative and preventive effects of 15 fungicides on gray mold disease, Botrytis cinerea, by means of the spore inoculation method with cucumber cotyledons as test material and paper discs for inoculation. Treatment with iprodione, fludioxonil, azoxystrobin, and polyoxin provided a strong curative effect at 24 h after spore inoculation, but no fungicide was effective at 48 h after spore inoculation. Iprodione, fludioxonil, mepanipyrim, fenhexamid, boscalid, penthiopyrad, and azoxystrobin produced a strong preventative effect in a spore inoculation experiment at 21 d after fungicide application. We also performed a greenhouse experiment and confirmed that fludioxonil, boscalid, and a mixture of iminoctadine albesilate and fenhexamid were effective against gray mold disease on tomato plants for 21 d. The efficacy of these fungicides in controlling gray mold disease on strawberry plants was then confirmed in a farmer's greenhouse. Our study demonstrates that gray mold disease must be controlled by preventive spraying with fungicides that have a long residual control effect, treatment with fungicide after infection has already occurred is unlikely to be successful.