Like green peach aphid, we have found turnip aphid to be abundant this year on canola. These results have surprised us, but are encouraging. Last summer, the first PLRV-positive green peach aphids were collected 14 July. Results of the PCR testing of green peach aphids captured this past week will be reported next week. The absence of any positives for either PLRV or PVY in the aphids collected this year is consistent with our interpretation that these are migrants moving into the potato crop from hosts other than potato.
Aphids developing on potatoes are much more likely to acquire and transmit potato viruses.
Much current season transmission has already occurred. We believe that to date this has mostly been secondary transmission, i.e., within field transmission from plants grown from infected tubers. Last week we mailed a survey to Aphid Alert subscribers. The survey was mailed to 123 who receive Aphid Alert by U.S. mail and to 78 who receive the Aphid Alert by e-mail. There is some overlap of these two lists and some recipients are not directly involved in the potato industry.