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United States Department of Agriculture

Agricultural Research Service

Title: History of Pea Aphid Outbreaks on Peas in the Palouse

Author
item Clement, Stephen

Submitted to: Entomology Society of America Pacific Branch Meeting
Publication Type: Other
Publication Acceptance Date: November 27, 2004
Publication Date: N/A

Interpretive Summary: Field pea, Pisum sativum L., is a spring crop grown in rotation with cereal crops in eastern Washington and northern Idaho (Palouse region of the Pacific Northwest). The major insect pests of peas are the pea leaf weevil, Sitona lineatus (L.), pea seed weevil, Bruchus pisorum (L.), and the pea aphid, Acyrthosiphon pisum (Harris). An insect outbreak is an explosive increase in abundance over a relatively short period of time, a phenomenon first recorded in the 1930s and 1940s for the pea aphid on eastern Washington peas. During outbreak years, pea aphid-vectored viruses and feeding damage have been responsible for high pea seed losses in the Palouse. I developed a pea aphid outbreak index (0-4, where 0 equals 0-25% of pea fields with high populations and 4 equals > 76% of fields supporting high populations) based on suction trap counts, field sampling, incidence of virus epidemics, and grower contacts. Outbreaks (3 or 4 rating) have occurred on Palouse peas every seven (1983 to 1990) and six (1990 to 1996) years. In other years (1989, 1993, and 2004), pea aphid densities were high (2 rating), but did not reach outbreak levels (3 or 4 rating) between April and late-June.

Technical Abstract: Field pea, Pisum sativum L., is a spring crop grown in rotation with cereal crops in eastern Washington and northern Idaho (Palouse region of the Pacific Northwest). The major insect pests of peas are the pea leaf weevil, Sitona lineatus (L.), pea seed weevil, Bruchus pisorum (L.), and the pea aphid, Acyrthosiphon pisum (Harris). An insect outbreak is an explosive increase in abundance over a relatively short period of time, a phenomenon first recorded in the 1930s and 1940s for the pea aphid on eastern Washington peas. During outbreak years, pea aphid-vectored viruses and feeding damage have been responsible for high pea seed losses in the Palouse. I developed a pea aphid outbreak index (0-4, where 0 equals 0-25% of pea fields with high populations and 4 equals > 76% of fields supporting high populations) based on suction trap counts, field sampling, incidence of virus epidemics, and grower contacts. Outbreaks (3 or 4 rating) have occurred on Palouse peas every seven (1983 to 1990) and six (1990 to 1996) years. In other years (1989, 1993, and 2004), pea aphid densities were high (2 rating), but did not reach outbreak levels (3 or 4 rating) between April and late-June.

Last Modified: 7/28/2014
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