Trap Catches to September 05, 2025.
With 13 of 22 sites reporting, aphid numbers were up from our last report. Approximately 30% increase in the total capture of vector species and, averaged over the fewer traps reporting, a 50% increase in vector capture per trap location. Similar increases were seen in non-vector species, so aphid flight increased definitely had an upturn during the last trapping period. The continuing captures of green peach aphids resulted in another jump in both the total cumulative and regional average PVY Vector Risk Index.
Average green peach aphid captures per trap were similar to last week's and The Queen Of Vector Aphids remains well represented across the region. This late season appearance is very concerning and presents a risk to any field not yet vine killed. While most of our PVY transmission likely occurs later in the season when aphid flights peak, numbers of green peach aphids at this time are especially concerning.
Soybean aphid numbers were recovered at almost every location and the number per location rose. Cotton melon, buckthorn and thistle aphids were well represented and their numbers were all higher as well.
Historically, our numbers tend to crop the first or second week of September, and we had some colder nights this current week. Hopefully this will soon result in the development of winged generations that will leave the summer hosts. In the meantime, vector numbers remain high, so in those fields that are still green, take appropriate scouting and management steps.
Have a great weekend, 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.
Cumulative PVY Risk Index by Site to 8/29/2025
Aphid Species Capture and PVY Vector Risk Index for the week ending 8/29/2025
Cumulative Aphid Species Capture and PVY Vector Risk Index to 8/29/2025
