Codling Moth Parasitism Under Different Spray Treatments*

Abstract

A survey of codling moth larval parasitism in plots sprayed over a period of 3 yrs. with (1) lead arsenate-oil, (2) fixed nicotine-oil and (3) fixed nicotine alone, showed a build up in parasitism by Ascogaster carpocapsae of approximately 35% in the fixed nicotine sprayed plots, 27.0% in the fixed nicotine-oil sprayed plots and 5% in the Pb arsenate-oil sprayed plots. This indicates fixed nicotine sprays are less toxic to A. carpocapsae than lead arsenate. In another orchard where a fixed nicotine plot surrounded by Pb arsenate-oil sprayed plots was conducted for 1 season no A. carpocapsae parasitism was found in any plot. Where A. carpocapsae populations have been reduced to a low point by continuous yearly application of arsenicals, a change to sprays less toxic to the parasites will probably not show a build up of parasitism for several yrs.