Trap Catches Identified to September 04, 2020.
Aphid vector numbers were down this week, with increasing numbers of fields being vine-killed, fewer sites are reporting. The number of vector aphids recovered to this point in 2019 was only 2/3 of what we've captured in 2020. Consequently, as can be seen in the map and tables below, the regional PVY Vector Risk Index is higher in 2020 than it was this time last year. The numbers of certain species varies a bit this year, we've recovered fewer English grain aphids, but far more corn leaf aphids; the numbers of green peach aphids are very similar to last year but from different locations. Green peach aphids seem to be more dispersed this year, 10 of the 19 sites have recovered this species (which is the most efficient vector of PVY).
Importantly, this was the highest capture of green peach aphids we've seen so far this year. Soybean aphid captures were up this week; we've stated to experience cooler evenings and flights to buckthorn may well make up some of these numbers. Thistle aphid numbers were up this week, potato aphids and and small grain aphids are still well represented in the trap captures while damson-hop and cannabis aphids have decreased this week.
While many fields have already vine-killed, it's obviously important if you have green plants still in the field to be managing aphid vectors. Much of our within-field transmission of PVY probably occurs later in the season.
If you have a field where Colorado Potato Beetle aren’t being controlled by insecticides, please let us know. We’d like to get samples of that population to test for insecticide resistance. Contact Ian MacRae at 218-280-9887.
As always, keep on scouting!
Click on any image below for full-scale version.
Cumulative PVY Vector Risk Index to September 04, 2020.
Cumulative PVY Vector Risk Index to September 01, 2019 season (for comparison)