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Project description

Introduction and Evaluation of Parasitoids Attacking Aphids as a Component of the Developing IPM Program on Prunes in California. (96BU013)
Program UC IPM competitive research grants program
N.J. Mills, Environmental Science, Policy and Management, UC Berkeley
L.K. Etzel, Environmental Science, Policy and Management, UC Berkeley
Host/habitat Prunes; Tree Crops; Stone Fruits
Pest Aphids
Discipline Entomology
Biorational Use of Biotic Agents or Chemicals
Start year (duration)  1996 (Three Years)
Objectives Acquire, import, and produce nonindigenous species and biotypes of parasitoids that attack prune aphids.

Field release the parasitoids and then collect them from release sites for distribution to new localities.

Monitor parasitoid establishment and impact on pest aphids in prune orchards, and establishment on aphids on the obligatory alternate host plants in California.

Survey for and monitor the populations of native arthropod parasitoids and predators that attack prune aphids in California orchards and on their alternate host plants.

The mealy plum aphid, Hyalopterus pruni, and the leaf curl plum aphid, Brachycaudus helichrysi, are exotic pests which have become an important problem in prunes in California with the reduction of in-season insecticide sprays for peach twig borer (Anarsia lineatella). In April 1998, 210 individuals of a French strain of Ephedrus persicae were released against the plum leaf curl aphid in six prune orchards in Glenn, Butte, and Yolo counties, and mummies were recovered from two sites. From June to September, 1285 individuals of three Spanish biotypes of A. transcaspicus were released against the mealy plum aphid at eight prune orchard sites and two cattail (an alternate host) sites in Glenn, Butte, Sutter, Yolo, and Madera counties. A few A. transcaspicus mummies were recovered in spring from releases the previous season in the Winters area, but within-season recoveries were again erratic. Lab studies indicate that the Spanish biotypes of A. transcaspicus may not be well adapted to mealy plum aphid. A new parasitoid, A. magdae, collected from mealy plum aphids in Israel will be available for field release in 1999.

Detailed sampling of orchards to determine the abundance of aphids, indigenous predators and released parasitoids was performed from April until September in four orchards in Glenn, Butte, Sutter, and Yolo counties. Aphid populations were less abundant than in previous years but showed similar patterns of activity in relation to orchard age as seen in previous years. The dominant indigenous predators were the lacewing Chrysopa nigricornis, the ladybird beetles, Harmonia axyridis and Hippodamia convergens, and the predatory fly Leucopis sp.

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