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Development of Biological Control of Tetranychus urticae (Acari: Tetranychidae) and Phorodon humuli (Hemiptera: Aphididae) in Oregon Hop Yards

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Title Development of Biological Control of Tetranychus urticae (Acari: Tetranychidae) and Phorodon humuli (Hemiptera: Aphididae) in Oregon Hop Yards
Names Woods, J. L. (creator)
Dreves, Amy J. (creator)
James, D. G. (creator)
Lee, J. C. (creator)
Walsh, D. B. (creator)
Gent, D. H. (creator)
Date Issued 2014-04 (iso8601)
Note To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Entomological Society of America and can be found at: http://www.entsoc.org/Pubs/Periodicals/JEE.
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 9 yr (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 yr. Populations of aphidophagous coccinellids developed synchronously with hop aphid
populations, and temporal correlations indicated these are the primary predatory insect associated
with hop aphid regulation. However, sampling methods did not assess levels of aphid parasitoids and
hyperparasitoids and their contribution to biological control was unquantified. 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 7-14 d. 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 4 yr (2008-2011).
Natural enemy abundance in commercial hop yards was similar to that of a 2- to 3-yr-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.
Genre Article
Topic conservation biological control
Identifier 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. doi:10.1603/EC13488

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