Persistence and distribution of three benzimidazole fungicides in pear trees sprayed for the control ofventuria pirina

Abstract

The persistence and distribution in leaves and fruits of benomyl, carbendazim and methylthiophanate were investigated, following fungicide spray treatments in pear orchards. Chemical analysis and bioassays showed that basal leaves sprayed more than once with benomyl, contained 50 ppm of methyl benzimidazole carbamate (MBC) 4 days after the last spray. Seven months later. 8 ppm MBC was detected in the basal leaves, just before normal abscission. In apical leaves, the fungicide levels were lower than in the basal ones. Analyses of basal leaves showed that the residue level of MBC, 5 and 7 months after the last treatment with benomyl. carbendazim or methylthiophanate, was very similar in all treatments. Bound MBC was not detected in the leaves and only low concentrations of 2-amino benzimidazole (2-AB) were detected. There was no translocation of these fungicides from treated leaves to new young leaves. Chemical analysis of pear fruits from an orchard sprayed with benomyl revealed that 3 weeks after the last spray treatment, the residue level of MBC was 0.4 ppm. About 85% of the fungicide was found in the peel, and only 15% in the pulp. The more infected fruits consistently contained a lower concentration of MBC than the less infected fruits.