Trap Catches to August 01, 2025.

What a difference a week makes, again.... With 20 of 22 trapping locations reporting, total aphid vector captures were approximately 3 times that of last week.  This puts our cumulative seasonal capture about 1 week behind the 13 year regional average (see the graph below) and behind last year's population counts (see the maps below). 

Soybean aphid numbers went by 5, English grain aphids tripled, cotton melon aphid numbers doubled and non-vector species tripled as well. In the past week conditions for aphid population growth have been good, alternate host crops (especially small grains) have started to be harvested, and the lack of rainfall facilitated aphid dispersal. These are all conditions that occur about this time of year. And all contribute to the increased aphid vector activity we experience at this point in the late season.     

The regional weather outlook over the next week will likely cause a similar increase in aphid flights. Small grain harvest has commenced and small grain aphids are increasing their flight activity. Soybean aphid flights have started to ramp up, generally resulting in increasing visits to seed potato fields.  Like soybean aphid, other non-colonizing aphid species will be increasingly entering seed fields and, while they don't feed or reproduce on potatoes, will probe and transfer inoculum while they're visiting. The populations of several aphid species colonizing potatoes have increased so scouting is increasingly important at this point. Given the weather, their populations will be increasing and control of growing colonies may be required.   
So, keep scouting and checking the predictive sites!

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 (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 PVY Vector Risk Index by week for 2025. 

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). 

Cumulative PVY Risk Index by Site to 8/01/2025

 Cumulative PVY Vector Risk Index by Site to 8/02/2024 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 8/01/2025

Cumulative Aphid Species Capture and PVY Vector Risk Index to 8/01/2025