Here are the trap catches from the sites we received up to July 18. Note that sites are on different schedules to send in trap catches (spreading out our identification workload).
Nate reports that the warm weather has brought about higher aphid numbers, particularly in Ada, Crookston, Forest River, and Hatton. We've seen an increase in aphid numbers at almost all sites this week, although many sites still have very few aphids. Increased numbers have been mostly bird cherry oat aphid and green bug and probably represent aphids leaving maturing small grains in the region. Fortunately, we are still not seeing green peach or soybean aphid.
The Sabin trap has not been functioning correctly (the fan wasn't running). Make sure you are scouting in this area as we have not been able to get accurate counts. The problem has been fixed and next week’s numbers should accurately reflect vector numbers in the area.
So 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.