Conservation Biology of Syrphids, Predators of Woolly Aphid in Central Washington.

CSANR Project 051

Status: Complete

Project Summary

Woolly apple aphid Eriosoma lanigerum is a secondary pest whose outbreaks have occurred more often since about 2000. The increase in aphid outbreaks appears to be associated with the changes in pesticide programs and disruption of biological control. Nevertheless, there is a good opportunity for biological control of this pest in orchards under “soft” pesticide programs. A preliminary survey of natural enemies conducted in 2008 has indicated that syrphids (Diptera: Syrphidae) are one of the most common predators found in woolly apple aphid colonies. One approach to enhance biological control is the conservation of natural enemies. This may be achieved by altering crop systems to provide necessary resources for beneficial insects. Adult syrphids are known to rely on the ingestion of nectar for energy and pollen for gametogenesis. Thus, engineering the orchard ecosystem to include flowering plants that provide these resources to adult syrphids should enhance biological control. The effect of sweet alyssum Lobularia maritima on the attraction of syrphids, and suppression of woolly apple aphid were examined in 2008 and 2010 respectively. Alyssum showed a high attraction to predatory syrphids. In addition, a faster aphid control was observed on alyssum plots compared to the check plots (grass). In 2011, we investigated the movement of natural enemies (especially syrphids) between alyssum and the canopy of the apple trees. Almost 50% of all syrphids, chrysopids and Aphelinus mali collected from the tree canopy tested positive for the marker, indicating movement of natural enemies between the cover crop and the tree canopy. This is further positive evidence to support the benefit of a flowering cover crop for enhancement of biological control in the apple system.

Annual Entries

2009

Principal Investigator: Elizabeth Beers
Additional Investigator: William Snyder
Graduate Student: Lessando Gontijo
Progress Report: http://www.tfrec.wsu.edu/pdfs/P1836.pdf
Grant Amount: $10,934

2010

Principal Investigator: Elizabeth Beers
Additional Investigator: William Snyder
Graduate Student: Lessando Gontijo
Progress Report: http://www.tfrec.wsu.edu/pdfs/P1849.pdf
Grant Amount: $13,000

2011

Principal Investigator: Elizabeth Beers
Additional Investigator: William Snyder
Graduate Student: Lessando Gontijo
Progress Report: http://www.tfrec.wsu.edu/pdfs/P2529.pdf
Grant Amount: $13,000

Publications

Gontijo, L. M., Beers, E. H., Snyder, W. E. 2011. Effects of flowering plants on syrphid attraction and woolly apple aphid suppression. Western Orchard Pest and Disease Management Conference, 12-14 January, 2011, Portland, OR.

Gontijo, L. M., Beers, E. H., Snyder, W. E. 2010. Biological Control of woolly apple aphid in Washington State. Washington State Horticultural Association Annual Meeting, 6-8 December, Yakima, WA [poster].

Gontijo, L., and E. H. Beers. 2009. Stop and smell the flowers: An approach to attract syrphids into apple orchards, In Entomological Society of America Annual Meeting, 13-16 December, 2009, Indianapolis, IN.

Gontijo, L., E. H. Beers, and W. E. Snyder. 2009. Conservation biology of syrphids, predators of woolly apple aphid in central Washington, 83rd Annual Western Orchard Pest & Disease Management Conference, [poster].

Beers, E. H. 2009. Cover crops: Inviting Natural Enemies into Your Orchard 6th International IPM Symposium, 24-26 March, 2009, Oregon Convention Center, Portland, OR.

Gontijo, L. M., Beers, E. H., Snyder, W. E. 2008. Conservation biology of syrphids, predator of woolly apple aphid in central Washington. BioAg Meeting, October 2008, Pullman, WA, [poster].

Additional Funds Leveraged

An OREI grant was submitted in February 2011 (pending; $2,989,473) that will investigate the effects of planted habitats on biological control of aphid pests of tree fruits (including woolly apple aphid.

Impacts and Outcomes

This method was adopted by three large organic growers in central Washington with significant woolly apple aphid problems, who reported success with the technique (reduced aphid problems).