Aphid monitoring project update – July 5th, 2013

Tuesday, July 9, 2013

If I could give this newsletter a title that would capture my main message it would be “stay vigilant”. We are still in the high risk flight window for virus transmission and we continue to catch significant numbers of winged aphids in our traps around the province. However, we are also in the thick of harvest and it is easy to let down our guard during this time. Unfortunately, this is not the time to do so as those winged aphids could well be carrying virus and spreading it/them through your fruiting and newly planted fields. 

Note in the graphs below that the aphid flight began on June 10th in Valley/Southwest NS and that total winged aphid catches are still rising after four weeks. Fortunately, less than 10% of these catches have been strawberry aphid, the primary vector that spreads the viruses, with only 5% in this week’s data. The aphid flight in Central/Eastern NS began on the week of June 17th, a full week later than Valley/Southwest, and 4% of these catches have been strawberry aphid, a slightly lower percentage than Valley/Southwest overall.  It will be interesting to see when the flights collapse in the two regions but my expectation is around mid-July in the Valley/Southwest and late July in Central/Eastern. Until then we have to maintain our vigilance on strawberry aphids management and monitor and spray as required.

Let’s talk about aphid management options at this point in the season. If you used the Admire soil drench option on your new fields earlier in the season it will be wearing off after 3-4 weeks and will no longer be protecting your new plants. As noted above we are still in the flight period of strawberry aphid and we need to spray regularly at least until this flight collapses. Options include Thiodan/Thionex and Cygon/Lagon and each should have activity for about a week. Hopefully the flight will collapse by mid-July and only a couple of sprays would be required.

What about fruiting fields? Well, we only have one control that has a short enough pre-harvest interval to be used during harvest and this is Assail (1 day PHI). It can be applied twice per season so you should only apply it if monitoring warrants its use. Excellent post-harvest options include Admire (2 foliars allowed assuming it was not applied previously as a drench), Thiodan/Thionex, and Cygon/Lagon.

Thank-you for your cooperation during the virus sampling over the last three weeks. Results are still coming in so I cannot give a comprehensive report at this time but stayed tuned and hopefully by my next newsletter I will have something for you. In the meantime, I am trying to communicate test results to individual farms as I receive them but am somewhat behind on this. If you are especially eager to know your results you can speed up the process by contacting me directly.  Until then “stay vigilant”!