2010 Annual Report 1a.Objectives (from AD-416) Develop integrated pest management for insects vectoring diseases in Pacific Northwest potato crops. 1b.Approach (from AD-416) Determine susceptibility of different potato plant growth stages to BLTVA phytoplasma under field conditions using leafhopper exclusion and exposure studies. Determine susceptibility of different potato plant growth stages to BLTVA phytoplasma under field conditions by timing applications of selected insecticides targeted against the beet leafhopper. Assess the impact of the timing of BLTVA infection on the potato yield, tuber processing quality, and phytoplasma transmission rate in daughter tubers. Develop treatment (action) thresholds for the beet leafhopper to reduce incidence of purple top disease in Columbia Basin potatoes. Documents Reimbursable agreement with WA State University (CSREES). Log 39493. 3.Progress Report The project goal is to develop management strategies for beet leafhopper and potato purple top disease. Several insects, including aphids and beet leafhopper, are serious pests of potato in the Pacific Northwest. The objective of this research project is to develop integrated pest management for potato insect pests in the Pacific Northwest. The following research contributed to developing management strategies for beet leafhopper-transmitted virescence agent (BLTVA) phytoplasma that causes potato purple top disease and is vectored by the beet leafhopper:. 1)we determined the susceptibility of potato plant growth stages to BLTVA phytoplasma infection under field conditions using leafhopper exclusion and exposure studies, and determined the relationship between beet leafhopper density and the likelihood of BLTVA transmission and purple top development;. 2)accurately determined the timing of insecticide sprays targeted against the beet leafhopper;. 3)determined the impact of the timing of BLTVA infection on the potato yield, tuber processing quality, and phytoplasma transmission rate in daughter tubers; and. 4)developed treatment (action) thresholds for the beet leafhopper to better manage purple top disease in Pacific Northwest potatoes. Preliminary data indicate that younger potato plants are more susceptible to BLTVA phytoplasma and as few as one infective beet leafhopper per plant can cause purple top disease. This project addresses objective 3 of the Potato CRIS. Monitoring of activities and progress on this project was accomplished by direct supervision of on-site employees, and use of site visits, e-mail and telephone to communicate with off-site collaborators.