Another week with high aphid pressure. We are seeing more green peach aphid across many sites including a whopping 18 from the Sabin trap! Soybean aphid numbers are still high. Several locations have risk indices in the double digits: Ada, Perham, Sabin, and Tappen.
As always, keep scouting!
The PVY Vector Risk Index numbers on the table represent the amount of pressure in comparison to green peach aphids that is occurring at any given site. The cumulative seasonal PVY-VRI up until Aug 17 for all sites is presented on the first map, the second is the total regional PVY-VRI from 2014.
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.