Trap Catches Identified Week of Aug 15-19
Another week of low numbers of aphid vector species in most locations. The exception was central and West Central Minnesota where traps in Staples and Verndale collected 23 and 52 respectively (mostly Bird Cherry Oat aphids), the Perham trap recovered 6 and the Sabin trap recovered 11 aphid vectors. Verndale and Sabin each had 1 green peach aphid in their catch this week and Crookston had 2. Soybean aphids were recovered in Sabin, Staples and Verndale as well, but not in excessive numbers. We have not yet seen a large flight of soybean aphids from the south and as the temperatures get lower and soybeans continue to mature, we may well soon be seeing decreased soybean aphid numbers.
But the catches in Central and West Central MN do indicate there's still aphids out there and much of our PVY is vectored later in the season. As always, keep scouting....
Scouting for aphids in potatoes: - Select leaves from the lower to mid canopy. Lower, older leaves will have more established colonies and aphids prefer the balance of nutrients found here; aphids are rarely found on leaves in the upper canopy.
- Avoid leaves on the ground or in contact with the soil. - In seed potatoes there is only a threshold for PLRV (10 aphids/100 leaves), reactive application of insecticides an effective control for PVY. - The use of feeding suppressing insecticides, such as pymetrozine (Fulfill®) or flonicamid (Beleaf®) and refined crop oils, such as Aphoil and JMS Stylet Oil, at or prior to field colonization by aphids may reduce the transmission of PVY within fields. Some other insecticides, such as clothianidin (Belay®), imidacloprid (Admire Pro® or Provado®), and spirotetramat (Movento®), have also been demonstrated to reduce the transmission of PVY. - In table stock potatoes, a treatment threshold of 30 aphids /100 leaves should deter yield loss due to aphid feeding.
The PVY Risk Index Index Not all species of aphid are equally efficient at transmitting PVY, some are better than others (green peach being the most efficient vector of PVY). So, the total number of aphids in a trap don't necessarily reflect just how much vector pressure there is at that location. The PVY Vector Risk Index compares aphid numbers, incorporating their relative vector efficiency compared to the Queen of PVY vectors (green peach aphid!). Using averaged reference comparisons from the literature, we multiply the number of each aphid species captured by it's efficiency camopred to Green Peach Aphid to more accurately depict risk posed by the species being trapped. We then sum the totals. The PVY-VRI values are presented on the tables below but also on maps comparing current cumulative risk to the total risk from the sample sites of last year (to compare with your local winter grow out results). Click on the map for full sized image...
Aphid Alert Trap Catch Identified Week of Aug13-19
The Seasonal Aphid Alert Trap Catches to Aug 19, 2016