Submitted to: Western Orchard Pest and Disease Management Conference
Publication Type: Abstract only
Publication Acceptance Date: 12/10/1999
Publication Date: 1/5/2000
Citation: Pfannenstiel, R.S., Unruh, T.R. 2000. Landscape affects leafroller parasitism. Western Orchard Pest and Disease Management Conference. p.35. Interpretive Summary:
Technical Abstract: Several parasitoids attack leafroller larvae in Washington orchards. These parasitoids depend on leafroller hosts in non-orchard habitats. Ancylis comptana is an overwintering host of C. florus. We studied the impact of A. comptana feeding in wild roses on parasitism in orchards. Parasitism of leafrollers along a transect from the roses to orchards was determined. Parasitism by C. florus was low through the spring; during June A. comptana became suitable and were parasitized by C. florus. When these parasitoids emerged from the roses, parasitism jumped from <20% to near 100% of leafrollers in the rose patch and increased to 65% in the nearest orchard site. Subsequently parasitism declined in roses as C. florus abandoned the rose patch and at this time was near 100% in orchards. The impact of orchard type, management regime and non-orchard habitats on parasitism of leafrollers was studied. Two areas were studied, one dominated by Mating Disruption (MD) and soft pesticide programs and the other a mosaic of MD and conventional regimes. In both areas, parasitism was low during the first leafroller generation. Parasitism during the second generation increased to 90.6% in riparian areas and 25 to 45-fold at the MD site. Parasitism was higher in orchards near riparian habitats. In the more conventional area, parasitism increased only 0 to 4-fold. Different parasitoids dominated in the MD and conventional sites.