Trap Catches Sept 06 - Sept 13, 2024.
As the season winds down and only 3 sites reporting this week, aphid vector numbers again decreased. The average number of vector aphid species recovered per location is less than half that of last week, and the average PVY Vector Risk Index values at each location reflect that decrease. Our average regional numbers are close to the 2012-2023 average (see chart below).
Most locations have already vine killed and movement from other cropping systems is also declining significantly. Even soybean aphids were low. Good news after late season flights.
For those few locations that have not yet vine killed, remember, virus transmission remains a concern as long as plant material is green and circulating.
Bottom line - this will likely be the last week of trap contents coming in. Our regional populations this season closely matched the 2013-2023 average for both aphid vector numbers and PVY Vector Risk Index values in pattern and magnitude.
The top chart shows the average regional aphid vector captures/trap and PVY Vector Risk Index to Sept 13, 2024. The lower graph shows the regional average aphid vector captures/trap and PVY Vector Risk Index averaged from 2012 to 2023. The dates are expressed in ISO Week numbers (a standardized method of presenting dates across years).
Scouting for aphids in potatoes:
- Select leaves from the lower to mid canopy. Start at the edge of the field.
- 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.
The PVY Risk Index Index
Not all species of aphid are equally efficient at transmitting PVY, some are better than others (green peach being the most efficient vector of PVY). So, the total number of aphids in a trap don't necessarily reflect just how much vector pressure there is at that location. The PVY Vector Risk Index compares aphid numbers, incorporating their relative vector efficiency compared to the Queen of PVY vectors (green peach aphid!). Using averaged reference comparisons from the literature, we multiply the number of each aphid species captured by its efficiency compared to Green Peach Aphid to more accurately depict risk posed by the species being trapped. We then sum the totals. The PVY-VRI values are presented on the tables below but also on maps comparing current cumulative risk to the total risk from the sample sites of last year (to compare with your local winter grow out results).
Scouting for aphids in potatoes:
- Select leaves from the lower to mid canopy. Start at the edge of the field.
- 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.
Click on any image below for full-scale version.
Cumulative PVY Vector Risk Index to 9/13/2024
Cumulative PVY Vector Risk Index to 9/08/2023 for Comparison
Aphid Species Capture and PVY Vector Risk Index for the week ending 9/13/2024
Cumulative Aphid Species Capture and PVY Vector Risk Index to 9/13/24
