While trap captures were still significant, the numbers captured at many locations were down this week (with 5 locations yet to be sorted and ID'd). The two sites that had increased captures (Gully and Perham) had big increases, in the case of Gully, most of these were bird cherry oat aphids. There were no green peach aphids recovered at this time but soybean aphids were recovered from traps in Hoople, Hatton, Forest River, and Linton, ND and Perham and Staples, MN. in most years, numbers of soybean aphids can be expected to increase and their distribution to broaden later in the season so these numbers are not surprising.
Cereal aphid captures remain high with bird cherry at and English grain aphids being common in most locations. Likewise, non-vector species also were numerous in the traps this week, indicating aphid movement is still active for many species.
So, vector pressure continues - if you have not yet vine killed, then...
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)