BASIS FOR USE STRATEGIES OF ANILINOPYRIMIDINE AND PHENYLPYRROLE FUNGICIDES AGAINST BOTRYTIS-CINEREA

Cyprodinil and fludioxonil are two new active ingredients for the cont rol of Botrytis cinerea, representing the two novel fungicide classes anilinopyrimidines and phenylpyrroles, respectively, with two new and different modes of action. While cyprodinil seems to interfere with th e synthesis of certain amino acids, the mode of action of fludioxonil is less well understood. To help design appropriate use recommendation s, the risk for resistance in B. cinerea against these two agents was assessed by establishing baseline sensitivities and by monitoring sens itivity of Botrytis to these two fungicides at various trial sites ove r a number of years. Monitoring was carried out at three sites in Fran ce and at one site in Switzerland where phenylpyrroles and anilinopyri midines were applied over five years in longterm strategy trials, eith er twice per season in mixture or once each as a single product in alt ernation. An additional site in Switzerland was monitored where anilin oyrimidines and phenylpyrroles had been applied three to four times pe r year in development trials starting in 1986. Monitoring with fludiox onil at all five trials sites over five years included 279 isolates fr om untreated and 702 isolates from treated plots. This monitoring did not show any changes in sensitivity to fludioxonil. Monitoring with cy prodinil over four years in the four long-term strategy trials include d 173 isolates from untreated and 482 isolates from treated plots. It revealed two isolates from France with reduced sensitivity in vitro an d in vivo, without however affecting performance of the products. At t he site in Switzerland where the development trials were carried out, a higher proportion of isolates with reduced sensitivity to anilinopyr imidines began to appear in 1993, which led to a reduced performance o f anilinopyrimidines applied alone in one trial. However, Botrytis con trol by a mixture of cyprodinil with fludioxonil remained excellent an d superior to the standards also in 1994. No cross-resistance exists b etween cyprodinil and fludioxonil. Also, strains with reduced sensitiv ity to the market products carbendazim, diethofencarb or vinclozolin s howed no cross-resistance to fludioxonil. Other studies had already sh own, that cross-resistance exists between cyprodinil and the other two anilinopyrimidines, mepanipyrim and pyrimethanil, but not between ani linopyrimidines and the market products mentioned above. The results o f these comprehensive studies form the basis for the use strategy prop osed by CIBA for the use of cyprodinil and fludioxonil against Botryti s. A prepacked mixture of the two new active ingredients is being deve loped and will be introduced worldwide for the control of Botrytis in grapes and vegetables. Copyright (C) 1996 Elsevier Science Ltd.