Weekly trap catches were down in all locations with the exception of Walhalla, ND (this may represent two weeks of samples). A significant number of these were green peach aphids.
Trap catches appear to be decreasing, indicating aphid movement is slowing. Nights have been getting colder and the movement of several species over the past two weeks may indicate many aphid vector species are moving to their overwintering hosts.
On notable exception to this general decrease in aphid populations is Walhalla, ND, which has effectively doubled its seasonal capture total in the past two weeks alone (102 vector species captured). As we did not receive a sample from Walhalla last week, this may indicate 2 weeks of capture. Approximately 10% of this capture were green peach aphids (11 total) although this was the only site to report this species this period. Also numerous were bird cherry oat aphids (18), thistle aphids (25), cotton/melon aphids (27), and buckthorn aphids (15). In addition there were numerous non-vector species in the trap indicating Walhalla had experienced significant aphid flight in the past 2 weeks. The two traps in Linton, ND receovered a total of 16 aphids between them and Gully, MN recovered 10.
The weekly total number of soybean aphids captured is down but they were still reported from 5 locations (Walhalla, both Linton site, Gully and Sabin).
Hopefully aphid captures will continue to decrease over the region over the next week. Several sites have already killed their adjacent fields so will no longer be reporting data.
Scouting & treating 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 standard broad-spectrum insecticides are not an effective control for PVY (by the time the aphid has been exposed and dies, it can have moved PVY inoculum into and, more importantly, within the field.
- the use of feeding suppressing insecticides, such as Fulfill (Syngenta Crop Protection) or Beleaf (FMC Corp.) 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.
- in table stock potatoes, a treatment threshold of 30 aphids /100 leaves should deter yield loss due to aphid feeding
* These trap catches sorted and ID'd in this report were trapped in the previous week. It generally takes 2 days to receive trap catches after being returned by a cooperator and then 1-2 days to be sorted and ID'd. The results will be updated again Aug 23. If needed, contact the lab at 218.281.8633 and ask for Ian or Nate...
Weekly Trap Catch (click on the image for larger version)
Cumulative Seasonal Catch (click on the image for larger version)