Five years' results from a long-term field experiment on carbendazim resistance of Pseudocercosporella herpotrichoides (Fron) Deighton

Abstract

In a field monitoring experiment, winter wheat sown in large plots with or without applications of carbendazim was used to determine, during 5 years in succession, the development of carbendazim resistance in field populations of Pseudocercosporella herpotrichoides (Fron) Deighton, ( Cercosporella herpotrichoides Fron). At the beginning of the experiment, one spore out of about 2·4 × 10 9 was resistant. This figure increased at a linear rate that was highly statistically significant. Eventually, the frequency of carbendazim-resistant conidia was of the order of 10 −8. The differences in the frequency of resistant spores in the carbendazim-treated and in the untreated plots were highly significant, ranging from twofold to eightfold, depending on the year in question. In practice, there seems to be little danger from carbendazim resistance in the eyespot fungus if normal plant-protection recommendations are followed.