2019 Volume 61 Pages 15-22
In order to elucidate the occurrence trends of resistant isolates of Botrytis cinerea and to conduct effective control, we collected isolates from 2015 to 2017 from tomato cultivation fields in Mie prefecture, Japan. We examined the chemical susceptibility of the isolates to major fungicides. In addition, we discussed the relationship between the application of fungicides and the occurrence of resistant strains.
In almost all of the investigation fields, resistant isolates to high-risk fungicides such as quinone outside inhibitors (QoI) and succinate dehydrogenase inhibitors (SDHI) were observed. The occurrence of resistance was frequent when using these fungicides. On the other hand, resistant strains to medium-risk fungicides, such as mepanipyrim, and to low-to-medium risk fungicides, such as fludioxonil, were not observed despite multiple sprayings. In other words, the occurrence trends of these major fungicides-resistant isolates were almost consistent with the risk defined by the Fungicide-Resistance-Action-Committee (FRAC).
In the fields where the generation of resistant strains was low, the use of protection fungicides such as tetra-chloroisophthalo-nitrile (TPN) and rotation spraying had been utilized.
We concluded that it is important to conduct susceptibility monitoring in order to verify the effect of the above measures against resistant isolates based on the FRAC risk.
