Trap Catches Sept 06 - Sept 13, 2024.

As the season winds down and only 3 sites reporting this week, aphid vector numbers again decreased. The average number of vector aphid species recovered per location is less than half that of last week, and the average PVY Vector Risk Index values at each location reflect that decrease.  Our average regional numbers are close to the 2012-2023 average (see chart below).  

Most locations have already vine killed and movement from other cropping systems is also declining significantly.  Even soybean aphids were low.  Good news after late season flights.

For those few locations that have not yet vine killed, remember, virus transmission remains a concern as long as plant material is green and circulating. 

Bottom line - this will likely be the last week of trap contents coming in.  Our regional populations this season closely matched the 2013-2023 average for both aphid vector numbers and PVY Vector Risk Index values in pattern and magnitude.

The top chart shows the average regional aphid vector captures/trap and PVY Vector Risk Index to Sept 13, 2024.  The lower graph shows 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).    

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 9/13/2024

Cumulative PVY Vector Risk Index to 9/08/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 9/13/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 9/13/24

 Trap Catches Aug 31 - Sept 06, 2024.

With 5 trap locations reporting, the average number of vector aphid species recovered per location has again significantly declined this week, as has the average PVY Vector Risk Index values at each location.  The early September drop in aphid numbers agrees closely with the 2012-2023 average of regional aphid population dynamics (see chart).  

While numbers are lower, important vector species remain in the trapping area.  Both Becker, MN and Crystal ND traps recorded green peach aphids this week.  Soybean aphids are lower but still widely distributed (both MN and ND sites reported this species). Other aphid species, including non-vectors, have decreased.  

Heavy aphid infestations in central MN commercial fields have continued, becoming wide spread in some fields.  Thee higher temperatures this week may continue to drive reproduction somewhat but the cool nights will ameliorate that increase.  Many fields have been vine killed and so this is not problematic.  For those that are continuing to grow and populations are difficult to control, several aphid-targeted insecticides may be effective; Transform (Cortev; sulfoxaflor), Sivanto Prime (Bayer Cropscience; flupyradifurone), or Sefina (BASF; afidopyropen) are all effective aphicides and have performed well in field trials.

For those locations that have not yet vine killed, virus transmission remains a concern as long as plant material is green and circulating. 

Bottom line - aphid populations and PVY Vector Risk significantly decreased again over the last week. Any field that is not yet vine killed remains susceptible to potential virus transmission...  

The top chart shows the average regional aphid vector captures/trap and PVY Vector Risk Index to Sept 06, 2024.  The lower graph shows 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).    

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 9/06/2024

Cumulative PVY Vector Risk Index to 9/08/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 9/06/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 9/06/24

Trap Catches Aug 23 - Aug 30, 2024.

With 6 trap locations reporting this week, the average number of vector aphid species recovered per location has significantly declined this week, as has the average PVY Vector Risk Index values at each location.  Our trap captures this week are about a week  earlier than the 2012-2023 average (see the chart below (see chart).  This has probably been the result of lower temperatures and increased rainfall. 

Soybean aphid captures, while still occurring at most reporting locations, are lower than the previous 2 weeks.  Likewise, small grain aphid numbers have dropped off as well.  Even non-vector species were less numerous.  

There have been reports, however, of heavy aphid infestations in central MN commercial fields.  These populations are experiencing high reproduction rates and attempts to manage their growth with synthetic pyrethroids have not been as successful as anticipated.  If synthetic pyrethroids are failing to control populations, it may be advisable to try aphid-targeted insecticides such as Transform (Cortev; sulfoxaflor), Sivanto Prime (Bayer Cropscience; flupyradifurone), or Sefina (BASF; afidopyropen). All three are effective aphicides and have performed well in field trials.

Some locations have already vine killed, but for those that have not, as long as plant material is green and circulating, the plant is still susceptible to feeding by aphids and potential virus transmission. 

Bottom line - aphid populations and PVY Vector Risk significantly decreased over the last week. Any field that is not yet vine killed remains susceptible to potential virus transmission...  

The top chart shows the average regional aphid vector captures/trap and PVY Vector Risk Index to Aug 30, 2024.  The lower graph shows 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).    

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/30/2024

Cumulative PVY Vector Risk Index to 9/02/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 8/30/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 8/30/24

   Trap Catches Aug 16 - Aug 23, 2024.

With 9 trap locations reporting this week, the average number of vector aphid species recovered per location is slightly down from last week, but the change in species resulted in a similar level of PVY Vector Risk Index.  Our numbers and PVY Vector Risk remain very close to the 2012-2023 average (see the chart below (see chart).  The 12 year average of aphid vector populations in MN & ND indicates decreasing numbers through the end of August, but presence persists into September. 

The only aphid species with a significant drop this week was soybean aphids.  Most other vector species numbers were down slightly from last week with the exception of buckthorn, black bean, and potato aphids.  The relative efficacies of soybean and the increasing species resulted in there being little change in the average PVY Vector Risk index from Aug 16 to Aug 23.  

Some locations have already vine killed, but for those that have not, remember the adage - If leaves are green, by aphids they're seen!  Yeah, corny, but true.  As long as plant material is green and circulating, the plant is still susceptible to feeding by aphids and potential virus transmission. 

Bottom line - aphid populations slightly decreased but the vector risk remained the same as last week. Meaning any field that is not yet vine killed remains susceptible to potential virus transmission...  

The top chart shows the average regional aphid vector captures/trap and PVY Vector Risk Index to Aug 23, 2024.  The lower graph shows 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).    

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/23/2024

Cumulative PVY Vector Risk Index to 8/25/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 8/23/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 8/23/24

  Trap Catches Aug 09-Aug 16, 2024.

With 11 traps reporting, the average number of aphid vectors captured per trap across the region remained similar to last week. There were, however, some important differences; the average captures of small grain aphids was slightly below last weeks, while the numbers of soybean aphids increased, especially at two trap locations. Our PVY Vector counts and PVY Vector Risk Index values remain behind those of 2023, and we continue to see very similar levels as the 12-year average for number of vectors per trap and PVY Vector Risk Index. The top graph below is the current regional average PVY Vector data to 08/16/2024, the bottom graph is the average PVY Vector data from 2013-2023.  The X-axis is the ISO week of the year, the graphs are arranged so the ISO weeks correspond. 

Soybean aphids continue to increase as their seasonal dispersal continues. This will likely continue until our nightly temperatures drop into the 40'sF.  Green peach aphid captures increased over last week, and were captured from 4 locations, with the trap at Becker, MN  returning 6 of the wee beasties. Small grain aphid numbers were lower than last week, which is not surprising given many locations are already harvesting wheat. As with last week, many of the aphid species recovered do not colonize potato. So, we'll keep counting for now.

Bottom line - The aphid populations were off to a slow start but we are now very close to the average 2012-2023 averages. The recent rains in some of our locations may slow aphid population growth but the 12-year average population declines don't occur until the end of the month.  

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/09/2024

Cumulative PVY Vector Risk Index to 8/11/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 8/16/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 8/16/24

 Trap Catches Aug 02- Aug 09, 2024.

With 13 traps reporting, we saw another jump in aphid numbers; with a total regional increase of about 70% more vectors captured this week than last.  The increased numbers were approximately even across all trap locations with the average increase in vector capture numbers being ~75%, with an average increase in PVY Vector Risk Index of ~43%.  While our PVY Vector counts and PVY Vector Risk Index values are well behind those of 2023, we're still on track compared our 12-year average for average number of vectors per trap and average PVY Vector Risk Index values. The top graph below is the current regional average PVY Vector data to 08/09/2024, the bottom graph is the average PVY Vector data from 2013-2023.  The X-axis is the ISO week of the year, the graphs are arranged so the ISO weeks correspond. 

Much of this week's capture was soybean aphids (5 times as many as last week).  As reported by Bruce Potter in his most recent IPM Stuff  newsletter (sorry to see that go, it was always informative and entertaining!  Thanks, Bruce for all you did!), soybean aphid populations have been rising in the south and the Sturgis Dispersal Event is underway (so called as it usually occurs right around the Sturgis rally time).  So a lot of the southerlies we've caught over the past week have likely been bringing our little soybean feeding friends (fiends?) up here.  

Green peach aphid captures were down this week, but many other species were up.  Small grain aphids continue to be numerous and even the number of non-vector species of aphids captured doubled over last week. Most of the aphid species vectoring PVY are non-colonizing species, they won't leave behind nymphs and there won't be colonies to let you know they've been in the field.  So, we'll keep counting for now.

Bottom line - it seems we're well into the typical August population increase for our area, and with the warming temperatures predicted for the next week, numbers will likely remain on the increase.  Remember, aphid vectors will continue to probe potato as long as it's green; consider the potential for PVY transmission to be present until vine kill...

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/09/2024

Cumulative PVY Vector Risk Index to 8/11/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/26/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/26/24

Trap Catches July 26 - Aug 02, 2024.

With 14 traps reporting, regional aphid vector numbers are very similar to those of last week and lower this point in 2023.  Total number of vectors remained very much the same although there were differences in the species collected.  There was one significant difference, the number of trap locations reporting Green Peach Aphid (GPA) has risen and the species was reported from several locations in the region.  This may represent recent rain systems coming from the south.  Along with similar numbers of aphid vectors, the PVY Vector Risk Index increased by an amount similar to last week.  Still, this represents an increase in cumulative seasonal risk.

New locations reporting GPA this week included Becker, Crookston, Forest River and Perham.  Lisbon, which has reported GPA already this season, captured 1 again this week as well.  So, while the numbers of GPA are low at each location, it's regional distribution may be increasing.  It appears the species is now present across most of the trapping area. Soybean aphids were numerous again this week as their late summer dispersal continues.  Small grain aphids continue to be numerous as do cotton/melon aphids.  

Temperatures are supposed to cool over the next week, but our nighttime lows will remain high enough that we will still be seeing aphid reproduction.  While the rate of population development will slow, it will likely not cease.  Aphid vector numbers may drop over the next few weeks, but the season is probably far from over.  In addition, existing populations remain.

As stated last week, proactive measures, such as the use of crop oils, are recommended through to vine kill.  As long as plants are green, they remain attractive to aphids that can vector inoculum.  The use of the insecticides Fulfill (active ingredient = pymetrozine) and Beleaf (active ingredient = flonicamid) have been shown to decrease the spread of PVY and also to be beneficial when use in conjunction with crop oils such as Aphoil or JMS Stylet oil.  

Bottom line, aphid numbers may (we hope!) drop over the next week, but they're still out there.  So... Keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to 8/

Cumulative PVY Vector Risk Index to 7/28/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/26/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/26/24

 

Trap Catches July 19 - July 26, 2024.

With 16 traps reporting, regional aphid vector numbers are still very similar to those of last year.  Aphid vector numbers more than doubled again this week and the regional PVY Vector Risk Index value doubled as well for the second week in a row.  Numbers continue to be tracking up at this point and are fitting our annual average pattern.

No new reports of green peach occurred this week.  However, soybean aphids appear to be moving a significant increase in captures this week.  In addition, numbers of English grain, corn leaf, and cotton/melon aphids were all up, as well as a number of other species, including non-vector species.  Warmer summer conditions have resulted in the development of winged aphids, and the maturing crops are moving them to alternate food sources..  

Those warmer temperatures are also going to shorten developmental cycles of wingless aphid colonies already established on crops.  Increasing colony size puts additional stress on their host plants, which can lower the plants nutritional value to the aphids. This also is a cue for the development of generations of winged aphids.  Given our average seasonal patterns of increasing temperatures through July and into August, it is hardly surprising we see our largest growth of aphid populations during this period (see the graph of the average seasonal aphid vector captures below).   

We expect aphid vector numbers will continue to rise over the next few weeks. As stated last week, proactive measures, such as the use of crop oils, are recommended at this time if not already started.  The use of the insecticides Fulfill (active ingredient = pymetrozine) and Beleaf (active ingredient = flonicamid) have been shown to decrease the spread of PVY and also to be beneficial when use in conjunction with crop oils such as Aphoil or JMS Stylet oil.  

Bottom line, aphid numbers are still increasing rapidly and are expected to continue over the next few weeks.  So... Keep on scouting!

Average Regional Total Vector Capture and PVY Vector Risk Index by Week 2012-2022 

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.

The PVY Risk Index Index

Not all species of aphid are equally efficient at transmitting PVY, some are better than others (green peach being the most efficient vector of PVY).  So, the total number of aphids in a trap don't necessarily reflect just how much vector pressure there is at that location.  The PVY Vector Risk Index compares aphid numbers, incorporating their relative vector efficiency compared to the Queen of PVY vectors (green peach aphid!).  Using averaged reference comparisons from the literature, we multiply the number of each aphid species captured by its efficiency compared to Green Peach Aphid to more accurately depict risk posed by the species being trapped.  We then sum the totals.  The PVY-VRI values are presented on the tables below but also on maps comparing current cumulative risk to the total risk from the sample sites of last year (to compare with your local winter grow out results).

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 7/26/2024

Cumulative PVY Vector Risk Index to 7/28/2023 for Comparison

Aphid Species Capture and PVY Vector Risk Index for the week ending 7/26/2024

Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/26/24