Trap Catches to August 22, 2025. 

With 15 of 22 sites reporting, aphid numbers are lower than the last trapping period with the average catch per trap roughly 2/3 that of last week. Green Peach Aphid were recovered at several sites across the region again this week (so check individual trap location captures below). Captures of non-vector species were significantly lower than last week's. The decreased vector capture has lowered our projected PVY Vector Risk Index; our numbers are now far lower than last year's at this point in time. Predicted lower night temperatures over the next week may signal several species to develop winged generations for dispersal back to overwintering hosts.

Green peach aphid numbers were low, but slightly more numerous than last week and were recovered from 4 locations. These and last week's reports indicate green peach is likely widely distributed at low levels across the region. The sudden increase of green peach aphid captures accompanying the widely distributed storms in the region over the past weeks raises questions about the potential of storm fronts contributing to late season aphid outbreaks. 

The continued capture of green peach aphids is concerning for both seed and production fields. Not only are they the most efficient vector of Potato Virus Y, but their rapid reproduction can lead to explosive increases in numbers. Last year, several locations across the region saw expanding aphid populations that caused yield impact.  Scouting both seed and production fields is strongly recommended.   

The most numerous aphid vector captured across the region this trapping period was again Soybean aphid although numbers were lower than last week's. Small grain aphids were still common, as were potato, cotton melon , and buckthorn aphids. 

The decrease in aphid captures is moving us lower than the 12yr average capture rates. If capture rates continue to decrease, we may end up at a lower risk than anticipated. But the widely distributed presence of green peach aphids means continuing scouting and management. 

 So have a great week, and keep scouting!

PVY Vector Risk Index - The ability of an aphid to transmit a virus is referred to as its vector efficiency, these values can be compared across species as a relative efficiency factor (also called the REF). Because data indicate it is the most efficient aphid species in transmitting PVY, green peach aphid's REF is set as 1, with other species' REF being calculated on their comparison to green peach aphid. E.g. soybean aphid has been found to be approximately 10% as efficient at transmitting PVY as is green peach aphid, so soybean aphid is assigned a REF of 0.1.  The PVY Vector Risk Index is a reflection of the comparative ability of the different aphid species to transmit PVY to plants. By multiplying the number of a species caught by its REF, we can estimate the risk from the total vectors captured, adjusted by the ability to transmit virus.

The usual reminders:

- keep scouting; aphids can establish early after potatoes are up. Field scouting is less effective at finding aphid vector species that don't colonize potatoes. While these species will enter potato fields and probe plants, they can't survive on potatoes, consequently they'll keep moving through the field, sampling additional plants and spreading inoculum in the field. Remember to check predictive sites like this one and University of Wisconsin's weather based Vegetable Disease & Insect Forecasting site,(https://agweather.cals.wisc.edu/vdifn) which uses current weather data and historical populations as a predictor of current aphid vector populations. These will give you a better idea of the potential presence of non-colonizing aphids. 
- the research literature reports that the use of crop oils is the most consistent post-planting technique in preventing transmission of PVY and it can be improved with the addition of the insecticide Lambda-Cyhalothrin.
- most of the research indicates that insecticides on their own are usually not effective enough at suppressing PVY transmission, but are still very useful parts of your management program. Treating fields with one of the anti-feeding insecticides (e.g. Sivanto Prime, Sefina, Transform, Fulfill or Beleaf) to control colonizing aphids, such as green peach, potato, or cotton melon aphids, can be beneficial in decreasing movement of PVY inoculum within fields
- aphids preferentially first colonize fields at the edge. Using border crops in the headlands may decrease aphid colonization. But if using a border crop, it's a good idea to use treated seed to prevent the development of potential vector species in that border.  Also, include those border crops when treating the field for colonizing aphids!

 Happy scouting and have a great weekend!

Click on any image below for larger-scale version.

The average regional PVY Vector capture and Cumulative PVY Vector Risk Index by week for 2025. 

Cumulative PVY Risk Index by Site to 8/22/2025

 Cumulative PVY Vector Risk Index by Site to 8/23/2024 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 8/22/2025

Cumulative Aphid Species Capture and PVY Vector Risk Index to 8/22/2025