Aphid numbers are up in some areas, down in others. We are still seeing high numbers of soybean aphid and higher numbers of green peach aphid that are contributing to high PVY Risk. Hopefully the recent cool weather will lower numbers for the coming week!
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 for trap contents identified up until Aug 24 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.