Welcome to the 2008 Aphid Hotline, sponsored by the Washington State Potato Commission and Washington State University. I’m Keith Pike, Research Entomologist with the University. This is the report for 5-Sep-2008.

Of 35 commercial potato fields evaluated for aphids and mites in the last week (see map below) —

5 (14%) fields were still green, actively growing, with moderate to high aphid counts, ranging from 10-100 aphids/plant (avg. = 38 aphids/plant);

15 (43%) fields were green or a majority of the plants were green, with low aphid counts ranging from 0-4 aphids/plant (avg. = 1.5 aphids/plant);

15 (43%) fields were at or near harvest, with vines 50-99% dead – for these fields aphid control is no longer meaningful;

The main aphid-virus threat in commercial potatoes in the Columbia Basin is now largely over. The exception is with fields that are still green, actively growing, bulking, and not scheduled for harvest anytime soon – these should be protected from aphids. Aphids left unchecked in green fields are likely to contribute to increased levels of potato leafroll virus (PLRV) and in turn, increased levels of PLRV net necrosis in stored tubers. For detailed information on seasonal PLRV impacts in potatoes, return to the home page and click on the article on Net Necrosis.

Aside from aphids, two-spotted spider mites are now common in most fields, and sometimes in heavy numbers. Mites, like aphids, are potentially damaging to potatoes that are still green and actively growing. For detailed chemical control recommendations for mites, return to the home page and click on the link to IPM Guidelines.

With the aphid season winding down, I wish to thank the various growers, fieldmen, and consultants that have assisted or allowed access to the different fields this year, and to the Washington Potato Commission for their support of the project, the hotlines and webpostings. As a reminder, all hotlines going back 9 years are posted on the WSU Aphid Website (these are available through the home page).

This is will be the final aphid hotline for 2008. If any late season aphid problems arise, and you have questions or concerns, please fell free to contact me at WSU-Prosser, 509-786-9269. Thanks.

NUMBER OF GREEN PEACH APHIDS PER PLANT 05 SEPT 2008