Tuesday, August 7, 2007

PS 37-188: Conserving and enhancing parasitoid natural enemies of leafroller pests in caneberries

Mario D. Ambrosino, Len B. Coop, and Paul C. Jepson. Oregon State University

The orange tortrix (Argyrotaenia franciscana Fernald) is a leafroller that has been a principle contaminant in machine harvested caneberries.  This leafroller is attacked by a large suite of parasitoid wasps, but the extent to which these parasitoids are affected by pesticides is unknown.  This four year project aims to conserve and enhance these parasitoid wasps by:  determining the incidence, timing and activity levels of the key parasitoid species in caneberry fields with different pesticide programs, investigating the direct effects of pesticides on these species in laboratory bioassays, and by developing improved monitoring practices and phenological models for key leafroller and parasitoid species.  A total of 120 fields in 2005 and 100 fields in 2006 were monitored for leafroller larvae and adults, and 7,291 leafroller larvae were collected.  Orange tortrix had 24.4% and 36.6% total parasitism in 2005 and 2006 respectively, and another leafroller species, the oblique-banded leafroller (Choristoneura rosaceana Harris), had 19.3% and 20.5% parasitism.  Parasitism of these leafroller species was consistently higher in fields that did not use broad-spectrum pesticides.  Further analyses of these data will determine species phenologies and if certain species are more or less sensitive to certain pesticide applications in certain fields.  The braconid wasps Apanteles aristoteliae Vier. and Meteorus argyrotaenia Johan. were responsible for over 2/3 of the orange tortrix parasitism and over half of the oblique-banded leafroller parasitism.  Cultures of these species have been established, and temperature development studies and pesticide bioassays are underway.

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