Control of the Walnut Aphid and Codling Moth on Walnuts in Northern California

Abstract

In northern California on most walnut varieties it is necessary to apply a regular seasonal spray to control the walnut aphid, Chromaphis juglandicola (Kaltenbach), and the codling moth, Carpocapsa pomonella (L.). It would be advantageous to the grower if a single compound would control both pests, as the timing of the first spray is the same for the 2 insects. Experimental field plots were established for 2 seasons to evaluate compounds that might serve this dual purpose. Phosphamidon, after trials in 2 seasons, and Bidrin® (3-hydroxy- N, N -dimethyl- cis -croton-amide dimethyl phosphate) in a single season of use, gave good control of both walnut aphid and codling moth. Endosulfan II (the high melting isomer of endosulfan) also showed promise against both pests while endosulfan was effective only against the walnut aphid. Morestan® (6-methyl-2,3-quinoxal-inedithiol cyclic carbonate) gave excellent control of walnut aphid and spider mites, but was not effective against codling moth. Dimethoate was an excellent aphicide, but caused phytotoxicity which would preclude its use on walnuts. Imidan® (phthalimidomethyl O, O -dimethyl phosphorodithioate) and Bayer 37344 (4-(methylthio)-3,5- xylyl methylcarbamate) controlled codling moth, but the walnut aphid increased on the plots to higher numbers than were recorded upon the unsprayed check. Both materials, especially Bayer 37344, were toxic to predators.