Extreme vector numbers in some locations
Aphid in several locations showed very high catches in the past week. Traps at Walhalla (101) and Hoople (165) and Staples (102) recovered from 2x to 5x their cumulative season's catch in just 1 week! Other locations also trapping higher numbers of aphid vectors than in past weeks were Cando (13) and Forest River (65), and Crookston (19). Gully recovered high numbers for the second week in a row (40). Non-vector aphid species were also numerous this week, indicating aphid dispersal was quite active.
Green peach aphids were recovered from only the trap in Cando while Soybean aphids were recovered Walhalla, Hoople, Forest River, Linton, Gully, Crookston and Staples. Soybean aphid is closely related to buckthorn aphid, sharing its overwintering host so it isn't surprising that buckthron aphid was recovered from numerous locatinos as well (Walhalla, Hoople, Linton, Lake of the Woods, Gully, Crookston, Sabin and Staples.
Several sites will no longer be reported as the vines in the adjacent fields have been killed and are likely no longer attractive to aphid vector species.
Late season vector pressure is increasing and late season transmission of PVY is thought to account for much of the infection in the region. Vector pressure continues.
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)