Although cooperating growers have done a great job managing their strawberry aphid populations over the last two weeks both of the project biologists have reported catches of winged strawberry aphids this week in matted row fields. The numbers have been very low but this does appear to be the beginning of the “spring flight” period for strawberry aphid this season.
What does it mean if winged aphids are found on your farm? In some cases this may mean that appropriate controls were lacking or were not effective and I would encourage the application of new controls as soon as possible as winged strawberry aphids are a much greater risk for virus transmission. On the other hand, on one farm where a winged strawberry aphid was found there were no wingless aphids so it is possible (and likely probable) that the winged aphid that was caught flew in from an outside source – an adjacent strawberry farm, home garden strawberry patch, or from wild strawberries. This notion reminds us that not all commercial strawberries farms are direct cooperators in the aphid monitoring project and that home-gardeners and wild strawberry sources of aphids are also excluded from our monitoring work. With regard to the former, I encourage all cooperators to talk to their neighbors and encourage them to monitor for strawberry aphid and apply controls if warranted. They may also direct them to contact me for advice as I may have a better idea of virus risk in their area. With regard to the possible source of strawberry aphids coming from home-gardeners or wild strawberries there is not a lot we can do other than continue to monitor our aphid populations and apply controls as we feel are needed.
What do winged strawberry aphids look like? There have been a few calls this week regarding suspicious looking winged insects found while scouting strawberry fields. Winged strawberry aphids actually look quite different from the wingless forms so a picture (Figure 1) and description is worthwhile. Firstly, they still have the knobbed hairs that distinguish the strawberry aphid from other aphid species. Also, they are more fly-like in appearance with a darker, more streamlined body with a distinct head, thorax, and abdomen as indicated in the picture below. Finally, the eyes are compound and black.
The final part of this update concerns virus testing conducted over the last week and a half. As reported earlier, we cannot do reliable virus testing early in the spring because virus titre levels are too low and we have to wait until temperatures warm-up and there is significant new plant growth. With the cold late spring this has meant that we have not been able to see any symptom expression (from 2012 infections) or do any lab testing until very recently. I began seeing virus-like symptoms about two weeks ago and have verified by lab testing that our two problem viruses are more widespread and at higher levels around the province than I had expected (or hoped). This reinforces the importance of our aphid monitoring and control work so please keep up the good work. I truly believe that with good management we will quickly return to normal production levels.
Once again, regarding aphid management options, please visit Perennia’s Strawberry Insect and Disease Management Schedule at http://perennia.ca/Pest%20Management%20Guides/Fruits/2013/Strawberry_Guide_2013.pdfor you may wish to review Pam Fisher’s (Berry Specialist, OMAFRA) article on aphid management at http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2013/03hrt13.pdf