Trap Catches to July 12 - July 19, 2024.
With 15 traps reporting, aphid vector numbers are still relatively low, but average aphid captures per trap did increase significantly over last week. Aphid vector numbers jumped by a factor of 4 and the regional PVY Vector Risk Index value almost doubled. Remember though, because we were at low populations last week, we remain at relatively low numbers. But numbers seem to be tracking up at this point.
A number of species increased across the region this week. Soybean aphids have started to increase in most locations as have small grain aphids. Potato aphids and cotton melon aphid numbers both increased this past week, as did the number of buckthorn aphids. Green peach aphid was again present in one trap location.
As the warmer weather continues and alternate crop hosts mature, especially small grains, vector numbers will likely continue to rise over the next several weeks. If not already started, proactive measures, such as the use of crop oils, should be considered and implemented. Research data* from Canadian researchers indicates the addition of an insecticide with the active ingredient Lambda-Cyhalothrin in crop oil applications may improve management of PVY spread. If implementing this tactic, keep in mind the dynamics of our aphid populations tend to later in the season than where that research was conducted. See the graph below for the average vector capture per trap and average PVY Vector Risk Index for 2012-2022.
Bottom line, aphid numbers are increasing and will likely continue to do so. So... Keep on scouting!
*MacKenzie, T.D., Lavoie, J., Nie, X. and Singh, M., 2017. Effectiveness of combined use of mineral oil and insecticide spray in reducing Potato virus Y (PVY) spread under field conditions in New Brunswick, Canada. American Journal of Potato Research, 94, pp.70-80.
Average Regional Total Vector Capture and PVY Vector Risk Index by Week 2012-2022
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 7/19/2024
Cumulative PVY Vector Risk Index to 7/21/2023 for Comparison
Aphid Species Capture and PVY Vector Risk Index for the week ending 7/19/2024
Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/19/2024
