Friday, September 9, 2022

 


Trap Catches to Sept 09, 2022.

Aphid numbers continue to decline as does the accumulation of PVY Vector Risk numbers.  Many locations have already vine killed or are getting ready to do so.  The season is rolling up to it's end, but the growth of aphid vector populations late in the season, especially the appearance of relatively numerous and well-distributed Green Peach Aphid, means this year ended with high PVY Vector Risk Index values.  The number of total vectors captured across the region was a little more than half that of last week, as was the total capture/trap.   

(Click on image for larger version)


Green Peach Aphid numbers were lower again this week, while there was a slight increase in Soybean Aphid and in Buckthorn Aphid captures over last week.  All of the cereal aphid numbers have dropped to the point they are only occasional captures and the only species with remaining relatively numerous numbers was Cotton/Melon Aphid.      

Have a great Weekend!  Keep scouting, and we'll keep counting...  The seasonal wrap-up will be out soon.

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 Sep 09, 2022

Cumulative PVY Vector Risk Index to Sept 10, 2021 (please note different scale)

Aphid Species Capture and PVY Vector Risk Index for the week ending Sep 09, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to Sep 09, 2022









Friday, September 2, 2022

 

Trap Catches to Sept 02, 2022.

Aphid numbers seemed to have peaked.  We recovered far fewer aphids per trap and overall regional numbers are way down this week, resulting in a decrease in the regional PVY Vector Risk Index.  It should be noted that this season's cumulative PVY Vector Risk Index remains significantly higher than that of 2021.

(Click on image for larger version)


Green Peach Aphid capture numbers were lower this week, approximately only 60% of last week's numbers.  But the species did increase their regional distribution this week, showing up at an additional two locations (Perham and one of the Staples trap locations).  

Soybean aphids are also down this week, dropping to almost half of last week, but are also well distributed across the region.  As the nights get colder, we should soon see temperatures that will trigger a movement from soybeans to Buckthorn.  

There was a drop off in the number of most cereal aphids, with only one English Grain aphid being recovered all week.  This is not surprising as cereal crops have matured in most locations and aphid dispersal from those crops will have ended.  The only exception was Bird-Cherry Oat aphid, the only species to have an increase in capture numbers this week (although it was only 4 more than last week...)  Other than that, all other species were captured at lower numbers.

The season is quickly winding down and many locations are vine killing and harvesting.  Hopefully, the aphid numbers will continue to rapidly drop, the weather will stay fine for harvest and the remaining few weeks will go smoothly.

Have a great Labor Day Weekend!  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.

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 Sep 02, 2022

Cumulative PVY Vector Risk Index to Sept 03, 2021 (please note different scale)

Aphid Species Capture and PVY Vector Risk Index for the week ending Sep 02, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to Sep 02, 2022

Friday, August 26, 2022

 

Trap Catches to Aug 26, 2022.

Another big week for aphid captures.  A total of 418 aphids were captured across all locations this week (350 of which were vectors of PVY), compared to only 316 last week (of which only 290 were vectors).  So our aphid numbers rose again this week.  Typically, our aphid numbers start to decrease by the last week in August.  It will be interesting to see what happens next week.

(Click on image for larger version)


A large number of Green Peach Aphids were recovered again this week resulting in a big rise in the Regional PVY Vector Risk Index.  Soybean Aphids continue to be active and were recovered at multiple locations.  Both Corn Leaf and English Grain Aphids continue to be numerous as do Thistle Aphids and Cotton/Melon Aphids.  Cannabis aphid captures have also increased this week.  

For the first time this year, the number of vector species aphids have surpassed that of 2021 and our PVY Vector Risk Index is more than twice that of this time last year.  The late season increase of aphids capable of vectoring PVY has made this a high risk year.  

Several locations in MN and ND have already been able to start vine kill.  But if there's still green material in the field, PVY can still be vectored by aphids.  So, given the number of vector populations present, appropriate management should be considered.   

So... 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.

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).

Click on any image below for full-scale version.


Cumulative PVY Vector Risk Index to Aug. 26, 2022

Cumulative PVY Vector Risk Index to Aug 27, 2021 (please note different scale)

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 26, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 26, 2022

Friday, August 19, 2022

 

Trap Catches to Aug 19, 2022.

What a difference a week makes.  The increasing presence and distribution of Green Peach Aphid in the region has driven the PVY Vector Risk higher than last year's at this time.    

Potato Virus Y is a non-persistent virus, aphid vectors acquire the virus when probing & feeding on an infected plant.  The aphid then transmits the virus to the next uninfected plant upon which it feeds.  Most of this transmission is by winged aphids, as they move through a field, testing plants to assess their value as a potential food host.  

Green Peach Aphid (GPA) is, by far, the most efficient vector of Potato Virus Y.  It can acquire the virus from an infected plant faster than other species of aphid and can transmit it more readily.  Consequently, it's presence increases the risk of PVY inoculum being moved in a seed potato field much more than does the presence of any other aphid species.  So, while the number of aphids being trapped this week that vector PVY are still below that of 2021, the importance of GPA as a PVY vector increases the Risk Index more than any other aphid that can vector PVY.  The weighting of increasing numbers of that species can be seen in the sharp rise of the seasonal increase in the accumulating average PVY Vector Risk Index of this season (right graph below) as compared to our 2013-2020 average (left graph below)

(Click on image for larger version)



Green Peach Aphids have been collected from a number of widely distanced locations and were numerous at several locations.  Overall, regional PVY vector captures increased again this week.  Trap numbers were almost 70% higher than last week, indicating we have not yet reached the population peak.  Other vector species are increasing in number and distribution as well.  Cereal aphids continue to rise and remain numerous at most locations, with all species increasing except Bird Cherry Oat Aphids.  Soybean Aphid capture numbers doubled this week and were recovered at all but 2 locations; Buckthorn Aphids were also numerous and recovered in most locations.  Both Damson Hop and Cannabis Aphids were recovered this week. Numbers of both Thistle and Cotton/Melon Aphids increased this week and were found at most locations.

With aphid vector numbers still increasing, and keeping in mind most of our PVY results from late season transmission, appropriate management tactics should be considered.  Monitoring aphid populations and keeping seed fields clean is increasingly important this time of year.

So... 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.

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).

Click on any image below for full-scale version.


Cumulative PVY Vector Risk Index to Aug. 19, 2022

Cumulative PVY Vector Risk Index to Aug 20, 2021 (please note different scale)

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 19, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 19, 2022





Friday, August 12, 2022

 

Trap Catches to Aug 12, 2022.

Another large jump in aphid numbers this week with an accompanying rise in the PVY Vector Risk.  The increase through August so far for this year's regional aphid population seems to mirror the average population growth from 2013 through 2020.  In other words, weekly captures are still increasing.  The total numbers of PVY vectors are still only half what they were at this point last year, but if the weekly increase in numbers continues, our total counts could be close to 2021.  The graphs below show the average regional weekly capture in 2021, the average regional weekly trap captures for this year, and the seasonal regional captures by week averaged from 2013 through 2020.  Note that in 2021 (upper left graph), by August, weekly captures had peaked and were decreasing, this year (upper right graph), half way through August and our weekly captures are still increasing.  The 8 year average pattern of weekly captures (bottom of the 3 graphs) indicates our typical peak occurs in August.        

(Click on image for larger version)
   

Soybean Aphid numbers continue to increase, as do our cereal aphid numbers with Corn Leaf and English Grain aphid numbers taking a bit of a jump.  Buckthorn Aphids were recovered from numerous trapping sites as were thistle aphids.  

Another single Green Peach Aphid was recovered from the trap in Becker, MN and there have been potential recoveries in Manitoba as well.  This indicates that there may have been at least a couple of immigration events this season.  Green Peach Aphids do not overwinter this far north, and their populations are re-established from the south only by very specific low-level jet wind events.  Looks like this has happened in at least two locations this year.  

In any case, numbers are rising, vector species are present.

So... 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.

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 Aug. 12, 2022

Cumulative PVY Vector Risk Index to Aug 13, 2021 (please note different scale)

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 12, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 12, 2022



Friday, August 5, 2022

 

Trap Catches to Aug 05, 2022.

Aphid vector numbers continued to rise this week, putting us into a later growing population than last year.  By this time in 2021, aphid captures had already peaked and were decreasing while this year's populations are still growing (see graphs below).  Last year's level of both aphid capture and PVY Vector Risk at this time of the season were much higher, mostly because of the number of English Grain Aphids which were numerous at all trapping locations in 2021.  The temperatures drought of 2021 drove aphid numbers high early in the summer.  This year, more moderate temperatures and more frequent rain have both moderated aphid population dynamics while providing better late season conditions for aphid populations in the area.  

(Click on image for larger version)

The species composition of the aphid captures are different this year, with no individual species dominating the catch to the extent that English Grain Aphid did last year.  That being said, Thistle Aphid was common this week and has become the most numerous vector captured this year and the only one to be recovered at all trapping locations.  Soybean Aphids are starting to increase and are being recovered from more trap locations.  This is not surprising for this time of year, Bruce Potter in Lamberton reported today that the southern migration has started this week.  We can probably expect more Soybean Aphids in our traps next week.  Cereal aphid numbers continue to rise, with the later maturing grain crop this year, these species also may well increase next week.  We also recovered our first Green Peach Aphid since 2020 this week.  Green Peach Aphid is, of course, the most effective vector of PVY.  Only a single Green Peach Aphid was recovered, lets hope she's lonely!
   

So... 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.

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 Aug. 05, 2022

Cumulative PVY Vector Risk Index to Aug 06, 2021 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 05, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 05, 2022