Monitoring of Residues of Benomyl on Leaves and Nut Hulls of Black Walnut. Steven Cline, Illinois Natural History Survey and Department of Plant Pathology, University of Illinois, Urbana 61801. Dan Neely, Illinois Natural History Survey and Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 65:961-963. Accepted for publication 30 March 1981. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-961.

The persistence of residues of benomyl and its degradation products on nut hulls and leaves of black walnut (Juglans nigra) trees was determined by cellophane transfer bioassays. In greenhouse studies, residues on leaves were determined following simulated rainfall at four levels applied weekly to incubator-grown walnut seedlings sprayed with benomyl at 0.6 g a.i./L. In field studies, residues on leaves and nut hulls were determined following spray treatments at 0.6, 1.2, and 2.4 g a.i./L. Benomyl at 0.6 g persisted (ED₁₀₀) on leaves of incubator-grown trees for 9 wk through 25 cm of simulated rainfall. Benomyl at this rate persisted (ED₅₀) on leaves and nut hulls of field-grown trees for 6 wk when rainfall did not exceed about 10 cm/wk. Higher rates of application did not add appreciably to residue persistence.

Keyword(s): carbendazim, MBC.