Trap Catches to July 31, 2026.

Aphid numbers took a huge jump in the past week. Aphid counts are up across the region with grain aphids leaving maturing wheat fields and soybean aphids starting their late July/early August dispersal flights. Regional PVY Vector Risk Index values have jumped with the populations and are now higher than at this point last year.  The increase occurred across the  trapping network with average captures per trap increasing at almost all locations reporting this week. This has resulted in an increase in average PVY Vector risk at all locations.   

We saw an increase in almost all vector species. The numbers of the 3 small grain aphid vectors most common to our area (bird-cherry oat, corn leaf and English grain aphids) increased at almost all trap locations. Other vector species such as cotton-melon and buckthorn aphids also saw a significant increase. Soybean aphids were by far the most numerous species at all locations, with some sites suffering very large flights this past week. Large soybean aphid flights are not unusual in MN and ND in late July and early August and are sometimes part of our late season PVY epidemiology. 

With much higher numbers of vectors present this week remember to scout and use appropriate management tactics.

 The usual reminders:

- vector flights have started, so continue 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 cannot survive on potatoes. Consequently, they'll keep moving through the field, sampling more plants and potentially moving inoculum already in the field to uninfected plants. Consult risk assesment sites (like this one) and check weather-based predicitve models like University of Wisconsin's Vegetable Disease & Insect Forecasting site (https://agweather.cals.wisc.edu/vdifn).

- 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 not effective enough at suppressing PVY transmission, but are still useful parts of your management program. Treating fields with one of the anti-feeding insecticides such as Sivanto Prime, Sefina or Transform to control colonizing aphids, such as green peach, potato, or cotton melon aphids, can be beneficial

- 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 and to include the border plants when applying foliar insecticides in the field.

Have a great week and keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Risk Index by Site to 7/31/2026

For Comparison, Cumulative PVY Risk Index by Site to 8/01/2025 

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/31/2026

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/31/2026

/2026

  Trap Catches to July 24, 2026.

Aphid vector numbers remain behind those of last year as does the PY Vector Risk Index. Average capture per trap was similar to that of the previous week (1.7 vectors/trap vs 2.2 vectors/trap last week) but the total number of vectors captured across the region has increased slightly. This reflects aphids being captured at more locations, albeit still at low numbers. 

Soybean aphids remain relatively common, being collected at most locations. Small grain aphids are beginning to become more common and Buckthorn aphids remain steady.

Expect more small grain aphids as the season progresses. While the return of high temperatures during the day may decrease reproduction rates, our night temperatures will be within good reproduction temperatures.

While trap numbers are low, aphid vectors are flying. Use appropriate management tactics.

Keep on Scouting.

 The usual reminders:

- vector flights have started, so start scouting; aphids can establish early after potatoes are up. Field scouting is less effective at finding aphd vector species that don't colonize potatoes. While these species will enter potato fields and probe plants, they cannot survive on potatoes. Consequently, they'll keep moving through the field, sampling more plants and potentially moving inoculum already in the field to uninfected plants. Consult risk assesment sites (like this one) and check weather-based predicitve models like University of Wisconsin's Vegetable Disease & Insect Forecasting site (https://agweather.cals.wisc.edu/vdifn).

- 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 not effective enough at suppressing PVY transmission, but are still useful parts of your management program. Treating fields with one of the anti-feeding insecticides such as Sivanto Prime, Sefina or Transform to control colonizing aphids, such as green peach, potato, or cotton melon aphids, can be beneficial

- 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.

Have a great week and keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Risk Index by Site to 7/24/2026

For Comparison, Cumulative PVY Risk Index by Site to 7/25/2025 

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/24/2026

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/24/2026

 

Trap Catches to July 17, 2026.

Aphid vector numbers continue to rise slowly but we remain far behind last year's populations. While the average number of vector species recovered from traps was up by 50% this week (2.2/trap this week vs 1.5/trap last week), the low numbers means that isn't yet a large increase. So vector aphid counts and the PVY Vector Risk Index remain relatively low. As a reminder, by July 18 last year, we had already recovered Green Peach Aphid from a number of locations and that species has not yet been collected this year. Soybean aphid numbers remain close to last year’s but we have yet to see a lot of movement from small grain aphids moving into potato fields. Potato and Pea aphids were both recovered from multiple locations, as were Buckthorn aphids.

Please keep in mind, this does not mean these low numbers will persist (yes, I know, I know... pest management is always doooom and gloooom!). Recent temperatures and weather conditions have not been optimal for aphid reproduction, which probably contributed to our low trap numbers. 

Aphid vectors are flying, temperatures across the region are edging back down which will facilitate higher rates of aphid reproduction, and there's certainly time left in the season.  Bottom line, keep scouting and using appropriate management tactics.   

The usual reminders:

- vector flights have started, so start scouting; aphids can establish early after potatoes are up. Field scouting is less effective at finding aphd vector species that don't colonize potatoes. While these species will enter potato fields and probe plants, they cannot survive on potatoes. Consequently, they'll keep moving through the field, sampling more plants and potentially moving inoculum already in the field to uninfected plants. Consult risk assesment sites (like this one) and check weather-based predicitve models like University of Wisconsin's Vegetable Disease & Insect Forecasting site (https://agweather.cals.wisc.edu/vdifn).

- 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 not effective enough at suppressing PVY transmission, but are still useful parts of your management program. Treating fields with one of the anti-feeding insecticides such as Sivanto Prime, Sefina or Transform to control colonizing aphids, such as green peach, potato, or cotton melon aphids, can be beneficial

- 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.

Have a great week and keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Risk Index by Site to 7/17/2026

For Comparison, Cumulative PVY Risk Index by Site to 7/11/2025 

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/17/2026

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/17/2026

  

Trap Catches to July 10, 2026.

More traps are starting to respond this week. We've had some technical difficulties, but we're sorting that out as we go. Apologies for this report being late, I've been out sick since last Thursday but am slowly on the mend. 

 The average number of vectors per trap doubled over last week (1.14/trap this week and ~0.5/trap last week) so the vector counts remain low. We are behind last year's populations at this date but we also have fewer traps responding so far. We'll get a better picture as more traps come online.

As far as species are concerned, English Grain and Soybean aphids were the most numerous species recovered. The average number of non-vector species also rose over the previous week. So we are staring to see the aphid populations build, pretty much on schedule... 

The usual reminders:

- vector flights have started, so start scouting; aphids can establish early after potatoes are up. Field scouting is less effective at finding aphd vector species that don't colonize potatoes. While these species will enter potato fields and probe plants, they cannot survive on potatoes. Consequently, they'll keep moving through the field, sampling more plants and potentially moving inoculum already in the field to uninfected plants. Consult risk assesment sites (like this one) and check weather-based predicitve models like University of Wisconsin's Vegetable Disease & Insect Forecasting site (https://agweather.cals.wisc.edu/vdifn).

- 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 not effective enough at suppressing PVY transmission, but are still useful parts of your management program. Treating fields with one of the anti-feeding insecticides such as Sivanto Prime, Sefina or Transform to control colonizing aphids, such as green peach, potato, or cotton melon aphids, can be beneficial

- 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.

Happy 4th and have a great upcoming week.

Click on any image below for full-scale version.

Cumulative PVY Risk Index by Site to 7/10/2026

For Comparison, Cumulative PVY Risk Index by Site to 7/11/2025 

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/10/2026

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/10/2026

 

Trap Catches July 03, 2026.

Our trapping networks are starting to return samples and numbers of aphid vectors per location remain low at this stage. However, weather fronts passing through the region, increasing temperatures and growing canopies will likely result in higher numbers over the next several weeks.

Soybean aphids were recovered at a couple of locations. Although their vector efficiency (the measure of how successfully they transmit PVY virus when compared to Green Peach Aphid) is relatively low compared to many other species, their high populations and tendency to move in high numbers means they are a very important vector of PVY in the North Central plains.   

The usual reminders:

- vector flights have started, so start scouting; aphids can establish early after potatoes are up. Field scouting is less effective at finding aphd vector species that don't colonize potatoes. While these species will enter potato fields and probe plants, they cannot survive on potatoes. Consequently, they'll keep moving through the field, sampling more plants and potentially moving inoculum already in the field to uninfected plants. Consult risk assesment sites (like this one) and check weather-based predicitve models like University of Wisconsin's Vegetable Disease & Insect Forecasting site (https://agweather.cals.wisc.edu/vdifn).

- 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 not effective enough at suppressing PVY transmission, but are still useful parts of your management program. Treating fields with one of the anti-feeding insecticides such as Sivanto Prime, Sefina or Transform to control colonizing aphids, such as green peach, potato, or cotton melon aphids, can be beneficial

- 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.

Happy 4th and have a great upcoming week.

Click on any image below for full-scale version.

Cumulative PVY Risk Index by Site to 7/03/2026

For Comparison, Cumulative PVY Risk Index by Site to 7/03/2025 

Aphid Species Capture and PVY Vector Risk Index for the week ending 6/27/2025

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/03/2026

 

Trap Catches June 26, 2026.

It's been  a slow start to the aphid trapping season. It's been a slow start to the aphid trapping season. With 5 sites reporting since mid-June, aphid vectors have been recovered at 4 locations. Aphids have started flying and so it's time to start scouting. Vector species were limited but included soybean, cotton-melon, pea and cotton-melon aphids. There were a few non-vector species recovered, but aphid captures / trap remain low.  Still, vector species are flying, so start scouting and checking the trap and predictive data.

The usual reminders:

- vector flights have started, so start scouting; aphids can establish early after potatoes are up. Field scouting is less effective at finding aphd vector species that don't colonize potatoes. While these species will enter potato fields and probe plants, they cannot survive on potatoes. Consequently, they'll keep moving through the field, sampling more plants and potentially moving inoculum already in the field to uninfected plants. Consult risk assesment sites (like this one) and check weather-based predicitve models like University of Wisconsin's Vegetable Disease & Insect Forecasting site (https://agweather.cals.wisc.edu/vdifn).

- 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 not effective enough at suppressing PVY transmission, but are still useful parts of your management program. Treating fields with one of the anti-feeding insecticides such as Sivanto Prime, Sefina or Transform to control colonizing aphids, such as green peach, potato, or cotton melon aphids, can be beneficial

- 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.

Happy scouting and have a great upcoming week.

Click on any image below for full-scale version.

Aphid Species Capture and PVY Vector Risk Index for the week ending 6/27/2025

 Trap Catches to September 12, 2025. 

With vine killing occurring throughout the region, only 8 traps reported this week. Average numbers per trap were well down (~1/3 of the last trapping period); it seems the September population crash is underway. While most species were represented across the region, average capture of all species was down. Vector species were still recovered however.
Green peach aphid was recovered at one location, soybean and buckthorn aphids were the most numerous species recovered across the region. Several other species were present at various locations. The colder nights are, however, likely decreasing activity and numbers are anticipated to decrease through the next couple of weeks. 
Have a great week, and hope your harvest is going well!

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 8/29/2025

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

 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.

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

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

 Trap Catches to August 29, 2025. 

With 19 of 22 sites reporting, aphid numbers were only slightly lower than the last trapping period but traps recovered almost twice the number of Green peach aphid across the region. This caused the PVY Vector Risk Index to bump up a bit despite lower numbers.  Green Peach Aphid were recovered at several sites across the region again this week; it is now widely distributed across the region with only 6 sites not capturing green peach aphid this summer. 

Captures of non-vector species were the same as last week indicating aphid flight is not yet decreasing. Our vector numbers and PVY Vector Risk Index are both still far below those of last year at this point in time. However, the late season rise in green peach aphid captures (of the season's 38 GPA captured, 28 were caught in the past two trapping periods) have resulted in higher populations of that species than past year.   

The continuing aphid captures does indicate the potential for aphid outbreaks in remaining commercial fields as well. So scouting both seed and production fields until vine kill is recommended.   

The most numerous aphid vector captured across the region remains to be Soybean aphid. Small grain, potato, cotton melon, and buckthorn aphids were all well represented in trap captures. 

Have a great Labor Day 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.

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

Cumulative PVY Risk Index by Site to 8/29/2025

 Cumulative PVY Vector Risk Index by Site to 8/30/2024 for Comparison

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

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