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United States Department of Agriculture

Agricultural Research Service

Research Project: Reducing the Impact of Diseases on Hop Production

Location: Forage Seed and Cereal Research

Title: Development of biological control of Tetranychus urticae (Acari:Tetranychidae) and Phorodon humuli (Hemiptera: Aphididae) in Oregon Hop yards

Authors
item Woods, J -
item Dreves, A -
item James, D -
item LEE, JANA
item Walsh, D -
item GENT, DAVID

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 8, 2014
Publication Date: April 30, 2014
Citation: Woods, J.L., Dreves, A.J., James, D.G., Lee, J.C., Walsh, D.B., Gent, D.H. 2014. Development of biological control of Tetranychus urticae (Acari:Tetranychidae) and Phorodon humuli (Hemiptera: Aphididae) in Oregon Hop yards. Journal of Economic Entomology. 107(2):570-581.

Interpretive Summary: Biological control can contribute substantially to management of certain agricultural pests. However, long-term data sets demonstrating development of biological control of arthropod pests are rare. In this study we report on the development of biological control of two spotted spider mite and hop aphid in hop over a nine year period. We find that both the abundance and diversity of natural enemies increased over time, and were able to identify the arthropods that likely contribute most substantially to regulation of these pests. Natural enemy abundance in the experimental plots was compared to those in commercial hop yards. Natural enemy abundance in commercial yards was similar to that of a 2-3 year old hop yard with limited disturbance. Whereas total reliance on biological control for hop aphid is unlikely to be successful, there appears to be unrealized potential for biological control of spider mites in commercial production.

Technical Abstract: The temporal development of biological control of arthropod pests in perennial cropping systems is largely unreported. In this study, the development of biological control of twospotted spider mite, Tetranychus urticae Koch and hop aphid, Phorodon humuli (Schrank) in a new planting of hop in Oregon is described over a period of nine years (2005-2013). Both the abundance and diversity of natural enemies increased over time. Known predators of hop aphid (Coccinellidae and Anthocoridae) were present in all years, however stable biological control of hop aphid was not achieved in most years and aphicides were required to suppress populations at commercially acceptable levels in 5 of 9 years. Populations of aphidophagous coccinellids developed synchronously with hop aphid populations, and temporal correlations indicated these are the primary predators associated with hop aphid regulation. Spider mite biological control was associated primarily with predatory mites (Phytoseiidae) and Stethorus spp. (Coccinellidae). The magnitude of temporal correlations of abundance of these predators with spider mites was found to be greatest on the same sampling dates and at lags of 7 to 14 days. Stable biological control of spider mites occurred after four field seasons, suppressing spider mites to levels similar to those commonly achieved with chemical control. A survey of 11 commercial hop yards in Oregon documented pest and natural enemy densities under commercial management practices over a period of four years (2008-2011). Natural enemy abundance in commercial hop yards was similar to that of a 2-3 year old hop yard with limited disturbance. Whereas total reliance on biological control for hop aphid is unlikely to be successful, there appears to be unrealized potential for biological control of spider mites in commercial production. Dynamic action thresholds that consider the value of natural enemies are needed for both pests.

Last Modified: 9/10/2014
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