Trap Catches to Sep 08 - Sep 15, 2023.

The trapping season is officially over.  This year's aphid vector populations rose steadily and then had the typical seasonal collapse in early September.  A complete Seasonal breakdown will be published next week.  

We hope harvest goes well for everyone!  

You keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 9/15/2023

Cumulative PVY Vector Risk Index to 9/09/2022 for Comparison

Weekly Aphid Species Capture and PVY Vector Risk Index for all sites reporting the week ending 9/08/2023

Cumulative Seasonal Aphid Species Capture and PVY Vector Risk Index for all sites to 9/08/2023

 

Trap Catches to Sep 01 - Sep 08, 2023.

With only 6 trap locations returning this week, the average aphid capture per trap is approximately half that of last week.  Far fewer vectors and non-vector species were recovered.  Many locations have harvested and shut down traps.  Once there's nothing in the field, the field becomes much less attractive to aphids, consequently aphid capture plummets and it makes no sense to continue trapping efforts.

Overall, very few aphids were captured.  It's notable that we still were recovering green peach aphid from one location and soybean aphids don't seem to have completed their move back to buckthorn for the winter.  Otherwise, no species was particularly numerous.  Next week will likely be the last capture date and will represent only several trap locations..

You keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 9/08/2023

Cumulative PVY Vector Risk Index to 9/09/2022 for Comparison

Weekly Aphid Species Capture and PVY Vector Risk Index for all sites reporting the week ending 9/08/2023

Cumulative Seasonal Aphid Species Capture and PVY Vector Risk Index for all sites to 9/08/2023

 

Trap Catches to Aug 25 - Sep 01, 2023.

Another week with much lower aphid numbers.  With 7 trap locations reporting, we continue to see a steady decrease in both total number of aphids, total number of vectors and average vector capture per trap decreasing.  The season is winding down with several trap locations having now vine killed and shutting down traps.  The total number of vectors and the regional PVY Vector Risk Index is almost double that of was at this time last year, so it's been a high vector pressure year.

Green peach aphids (GPA) were again recovered in 3 of the 7 sites.  English grain aphids are no longer being recovered while soybean aphids, although less numerous are well distributed across the region. Most other vector aphid species have decreased and non-vector species are also down.  

While this is good news overall, there are still vectors in the region and as long as vines are green, aphids will be attracted to them.  Consequently, green plants means the potential for transmission of virus still exists.  

You keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 9/01/2023

Cumulative PVY Vector Risk Index to 9/02/2022 for Comparison

Weekly Aphid Species Capture and PVY Vector Risk Index for all sites reporting the week ending 9/01/2023

Cumulative Seasonal Aphid Species Capture and PVY Vector Risk Index for all sites to 9/01/2023

 

Trap Catches to Aug 18 - Aug 25, 2023.

With 9 trap locations reporting this week, we've seen a big drop in capture numbers.  Not only are total regional captures are down (not surprising as some locations have vine killed), so are the average captures per location.  Last week , average vector counts per trap were 55.7, this week an average of only 23.7 vectors were captured per trap.  Some important vectors were recovered but the average per trap increase in the PVY Vector Index decreased as well from last week.  As we move into September, hopefully aphid vector numbers will continue to decrease. 

 

Green peach aphids (GPA) were again recovered in several sites this week and average numbers per trap were slightly higher than last week.  Average English grain aphid numbers per trap were only 20% of last week.  Soybean aphids, while still numerous and widespread were down by 60% per trap.  Most other vector aphid species saw either a decrease per trap or stayed roughly the same as last week.  Total regional vector capture this week was only 213 compared to last week's 780; this makes the average per trap capture 23.7 vector aphids per trap compared to last week's average of 55.7/trap.  

While this is good news overall, it should be noted that as long as vines are green, aphids will be attracted to feed on them.  Consequently, without vine kill, the potential for transmission of virus still exists.  it's still advisable to practice the appropriate precautions. 

So, you keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/25/2023

Cumulative PVY Vector Risk Index to 8/25/2022 for Comparison

Weekly Aphid Species Capture and PVY Vector Risk Index for all sites reporting the week ending 8/25/2023

Cumulative Seasonal Aphid Species Capture and PVY Vector Risk Index for all sites to 8/25/2023

 

Trap Catches to Aug 11 - Aug 18, 2023.

With 14 trap locations reporting this week, catches were down from last week (780 vector aphids this week, down from 891 last week).  However, due to the species captured, the increase in PVY Vector Risk Index was greater than that of last week (115.9 this week compared to 106.7 last week).  Much of this was due to greater numbers of green peach aphids being captured this week (23 this week compared to only 4 last week).  We are in a high vector risk year, far exceeding that of last year at this point.  In 2022, however, most of our vector capture came in the last two weeks of August.  Hopefully we won't continue that pattern. Our current pattern of trap catches does fit the pattern of the 2013-2020 average trap capture but is much higher (note the y-axis scale on the 2 graphs below). 

A total of 780 vector aphids were recovered in traps from August 11-14.  These included a rise in green peach aphid, the most efficient vector of PVY.  Green peach aphids were recovered from 6 locations, several of which were the same locations this vector was captured last week.  Soybean aphid captures were higher than last week, and, as with last week, were collected at all traps locations.  English grain aphids were recovered from all but one trap location and numbers were basically the same as last week (1 less...).  Potato, thistle, cotton/melon, and buckthorn aphids were all numerous and collected at most locations.   Many of these, especially green peach aphids, are very effective vectors of PVY, and their presence in high numbers skewed the PVY Vector Risk Index to be higher than last week's even though 110 more vector aphids were captured last week.  

As mentioned, last year's population mostly came on late in the summer, however, we've already exceeded both the cumulative number of vector aphids captured last summer.  Our PVY Vector Risk Index is also higher than last year's total.  The 2013-2020 averages do indicate late season increases are possible.  Hopefully the weather will cool, especially the night lows, and the populations will start to decrease.  But given the current situation, vector management is probably a good idea...

So, you keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/18/2023

Cumulative PVY Vector Risk Index to 8/19/2022 for Comparison

Weekly Aphid Species Capture and PVY Vector Risk Index for all sites reporting the week ending 8/18/2023

Cumulative Seasonal Aphid Species Capture and PVY Vector Risk Index for all sites to 8/18/2023

 

Trap Catches to Aug 04 - Aug 11, 2023.

And another big week for aphid flights!  Only 11 traps were reporting this week.  Several have been negatively impacted by last week's weather and may need some maintenance to get back online.  However, with 6 fewer traps reporting, our numbers of vector captures this week is only slightly below that of last week's 17 traps.  So, while the average number of vectors captured is slightly lower than last week, the average capture per trap increased by about 30% (average trap catch of all aphids last week was approximately 66/trap; this week's trap captures averaged 92 total aphids per trap).  All things considered, it looks like aphid flights ramped up this week.  A large part of this week's capture were vector species and, accordingly, the PVY Vector Risk Index took a large jump.  

All traps reporting collected soybean aphids this week, some at very high numbers.   Three geographically separated sites sites reported green peach aphids this week, although only single individuals.  Very high numbers of English grain aphid were captured again this week, trap locations close to small grain production areas were hit pretty heavy and suffered an increase in PVY risk.  Potato aphids were common as were thistle, cotton/melon, and buckthorn aphids. A variety of other vector species were present in lower numbers.  The overall aphid flight included a large number of non-vector species.  

This is the second week traps recorded high flight numbers of vector species.  This looks very much like the start of a high vector pressure late season.  Most of our PVY transmission in MN & ND likely occurs in late season (certainly that is the time of highest vector flight) and higher vector population at that time does increase the potential for disease transmission.  Consequently, appropriate measures such as antifeedant insecticides and the use of crop oils should definitely be considered.

The weather next week may be turning a bit warmer.  That may mean more flight activity which will increase probing on plants in the field.  Those locations close to traps reporting any of the species that colonize potatoes (esp green peach, potato, foxglove, buckthorn, and black bean aphids) should continue to scout for colonies.  Although non-colonizing species can be as, or more important vectors of PVY, scouting may not provide good estimates of their potential presence in fields.  However, note their presence in local traps in the network and that will provide some indication.

So, you keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/11/2023

Cumulative PVY Vector Risk Index to 8/12/2022 for Comparison

Weekly Aphid Species Capture and PVY Vector Risk Index for all sites reporting the week ending 8/11/2023

Cumulative Seasonal Aphid Species Capture and PVY Vector Risk Index for all sites to 8/11/2023

 

Trap Catches to July 28 - Aug 04, 2023.

It was another big week for aphids, and with this week's capture, this may turn into a heavy vector pressure season.  With 17 trap sites reporting, we saw regional vector trap captures almost triple over last week.  Not surprisingly, the PVY Risk Index followed suit with many of the vectors captured having relatively high efficiency in transmitting the virus.   

As the small grains mature, we're seeing large flights of English grain aphid, the most populous aphid in small grains this year.  By the 2013-2020 averages, the capture numbers generally double the first week of August over what was captured the previous week.  An while we're close to the average pattern, we're well above the average numbers for the first week of August.  Green peach aphids showed up in a number of additional locations and soybean aphids were recovered from all trap locations.

Green peach aphids were recovered from Cando, Lisbon, Crookston, Sabin and Perham.  Only Perham and Staples II site did not recover English grain aphids; this species was well into the double digits at several sites (a total of over 504 were captured from all traps together).  Soybean aphids tripled over last week, nearing 400 regionally.  Both thistle and Cotton/melon aphids were numerous and widespread this week, as were the non-vector aphids species, with traps recovering almost 400. While not contributing to the potential of PVY spread, the number of non-vectors species recovered does indicate just how heavy aphid flights were this week.

With the higher numbers, scouting is strongly advised.  But remember, non-colonizing aphid species (e.g. soybean aphid) will rarely be found in a field only by scouting.  They move through a field, sampling the plants, but not leaving any daughters on potatoes because it's an unsuitable host for them.  But they're still moving through the field, potentially moving any virus inoculum in the field.  So, it's a good time to start using crop oils if you haven't already, and to be thinking about anti-feeding insecticides as well (see below). 

So, you keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/04/2023

Cumulative PVY Vector Risk Index to 8/05/2022 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 8/04/2023

Cumulative Aphid Species Capture and PVY Vector Risk Index to 8/04/2023

 

Trap Catches to July 21-28, 2023.

What a difference a week makes, aphid numbers are way up...  Higher temperatures have driven aphid population development and is likely responsible for the increase in aphid flights we recorded for the last trapping period.  With 14 traps in MN and ND reporting, we had a total of 550 vector aphids captured in traps.  There were also high numbers of non-vector aphids recovered.  

We had the return of a single green peach aphids from Becker, MN.  The seasonal late season dispersal flights of soybean aphids has started with a total of 115 aphids from 12 of the 14 traps reporting.  English grain aphids, prominent in our small grains this season, are moving from small grains in search of alternate hosts as grain continues to mature; we recovered an overall total of 124 individuals with every site but two (Perham and Staples I) returning varying numbers.  The numbers and distribution of potato and thistle aphids were both up and cotton/melon aphids were also numerous and widespread. 

Along with the increased numbers, the PVY Vector Risk across the region rose, but wasn't consistent across all trap sites.  Compared to this time last year, both 2022 total aphids and vector species captured were about half of 2023 numbers.  Overall, this season's aphid captures seems slightly higher than the 2012-2020 average but still has roughly the same pattern of growth.  But, remembering last year's rapid late season increase in aphids, it's still too early to say what the rest of the season has in store...

So, you keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 7/28/2023

Cumulative PVY Vector Risk Index to 7/29/2022 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/28/2023

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/28/2023

 

Trap Catches to July 14-21, 2023.

With 14 traps reporting, we've seen a jump in aphid number this week.  A total of 81 PVY vectoring aphids were recovered.  Leading the vector species were English grain aphids and soybean aphids.  Much of the small grains are starting to mature with an associated decrease in food quality (from the aphids' point of view) and we can expect to see increasing numbers of grain aphids being capture in the traps.  Soybean aphids seem to also be on the move.

Our populations are similar to last year at this time and very close to the 2013-2020 average.  In most years, our aphid populations tend to rapidly increase through August.  During the growing season, aphids are all female and give birth to live daughters.  Colonies of aphids you find on plants are generally non-winged; they feed, have daughters and grow the colonies.  Crowded or a decrease in the food quality of their host plants triggers the development of winged forms that disperse to establish new colonies.  As average daily temperatures increase, aphid populations will tend to reproduce more rapidly, leading to increasingly dense aphid populations on host plants.  Consequently, the maturing hosts colonies feed upon through July and the associated higher temperatures drive the development of aphid colonies.  As the population gets larger, they not only get more crowded but feed more on their host.  The result is the creation of winged forms in multiple species during August.

Consequently, we may continue to see increases through the coming weeks. 

So, you keep scouting and we'll keep counting. 

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 7/21/2023

Cumulative PVY Vector Risk Index to 7/22/2022 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/21/2023

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/21/2023

 

Trap Catches to July 7-14, 2023.

With ten traps reporting in, aphid captures remain very low; only 12 vector aphids were captured.  We are starting to see the beginning of grain aphid flights.  The first soybean aphid was also recovered this week; not surprising given local populations lead us to we believe soybean aphids successfully overwintered in northern Minnesota and North Dakota this year.

The species of vectors that were captured this past week were generally less effective vectors and so the PVY Vector Risk Index remains low.  At this point last year capture numbers at several sites were higher and their and PVY Vector Risk values were almost twice what they are now (see below).

Warmer weather is predicted for the upcoming week, so aphid flights might heat up as well.  We'll see what the traps capture...

You keep scouting and we'll keep counting. 

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 7/7/2023

Cumulative PVY Vector Risk Index to 7/15/2022 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/14/2023

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/14/2023