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.   

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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.

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

 

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.

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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...

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

 

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.

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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...

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

 

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)

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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...

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

 

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.        

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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...

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

 

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.  

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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...

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

 

Trap Catches to July 29, 2022.

Aphid vector captures are up again this week, but the regional PVY Vector Risk is less than half that of last year.  While some sites this week are close to last year's numbers, far more sites had high numbers at this point last year than this year.  However, at this time last year, the vector population peaked and captures began to decline through August. This year's population seems to still be growing and our PVY Risk may continue to increase.  The graph below on the right shows the average number of PVY vector aphids caught across the region at this time last year, the graph on the left shows where those populations are this week.  Note the Y-axis range is very different, the 2021 populations were 2-3 times those of this year.  But in 2021, because of the hot, dry year, most aphid movement from small grains had already occurred by this time.  This year, many crops are behind where they were last year, there has been significantly greater moisture and conditions for continued aphid population growth through August are much better than in 2021.

The data below shows that for the first time this year, the number of vector species captured outnumbered the non-vectors. While many of these were cereal aphids (Bird Cherry Oat, Corn Leaf and English Grain aphids were recovered at several trapping locations) moving in response to maturing grain crops, a number of other vector species increased this week.  Potato aphids and Cotton/Melon aphids were numerous at several locations,  as were Buckthorn and Thistle aphids.  Soybean aphids, likewise, are starting to appear in low numbers at almost all trapping locations.

So, the more favorable weather for aphids we're experiencing may result in an associated increase in aphid numbers but so far, we're trending lower than last year.  Our typical peak aphid season is the next 2-3 weeks, lets hope our numbers stay low.

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

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 22, 2022

Cumulative PVY Vector Risk Index to July 23, 2021 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending July 29, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 29, 2022

 

Trap Catches to July 22, 2022.

Aphid vector captures are up this week over last week, but still behind last year's numbers.  This may be due to the wetter spring, which probably gave a boost to the fungal pathogens that often control aphid populations early in the year.  Last year, the dry conditions likely precluded the establishment of these natural controls in many areas.  This week, with most traps reporting, 74 vector aphids were recovered.  Still no Green Peach Aphids, but cereal aphids are getting more numerous and other aphid species are showing up as well.  With the increasing numbers, there was an increase in our regional PVY Vector Risk Index as well.

Most numerous were non-vector aphid species, indicating that the late July movement of aphids that we encounter in this region is underway.  Soybean aphid numbers are slightly increasing, with 9 sites reporting low numbers.  Cotton/Melon and Buckthorn aphids are both well-distributed across the region, Potato aphids were recovered at 6 locations as were Buckthorn aphids.    

The PVY Vector Risk Index, which reflects the risk of PVY transmission within fields based on the relative effectiveness or the aphid species' ability to transmit the virus, also increased this week.  Overall, our numbers are below where they were this time last year, but higher than 2020 or 2019.

It appears that our aphid numbers are following the standard pattern for our region, with populations starting to grow in mid-late July and peaking through August (see graph below).  If this is the case, we'll see increasing aphid populations over the next few weeks.

So... Keep scouting, we'll keep counting...

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 22, 2022

Cumulative PVY Vector Risk Index to July 23, 2021 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending July 22, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 22, 2022

 

Trap Catches to July 15, 2022.

Aphid vector captures remain behind those of last year, although trap captures are slightly increasing.  We started to see our first grain aphids and some other species, like thistle aphids, are starting to show up as well.  

Both Corn Leaf and English Grain aphids were recovered this week, indicating aphid movement from grains is starting.  Thistle aphids and Buckthorn aphids were recovered from a couple of traps.  Potato aphids and Cotton/Melon aphids are still present, and soybean aphids seem to be more widely distributed, although numbers are still low.    

Overall, the seasonal aphid abundance remains relatively low.  Early rains and wetter conditions than last year may be keeping populations down.  So a good thing to this point. 

Keep scouting, we'll keep counting...

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 15, 2022

Cumulative PVY Vector Risk Index to July 16, 2021 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending July 15, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 15, 2022

 

Trap Catches to July 08, 2022.

Aphid vector captures increased this week with more traps reporting and numbers at active sites slightly increasing.  We are still well behind last year with fewer aphids being recovered in traps than in 2021 (see the maps below for a comparison of this year and July 09 last year).  This is understandable given last year's drought played havoc with the fungal diseases that control aphid populations.  The spring rains and cooler temperatures this year hopefully allowed those fungi to rebuild and cause some mortality.  

Cereal aphids remain low as do soybean aphids.  Mostly we have recovered species that are associated with several other crop hosts; cotton melon and buckthorn aphids have been recovered in different locations.  The late planting in all cropping systems has probably contributed to the low aphid counts so far.  As always, as other crops start to mature, especially small grains, we can probably expect to see some more aphids finding their way into potato fields.     

Keep scouting, we'll keep counting...

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 08, 2022

Cumulative PVY Vector Risk Index to July 09, 2021 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending July 08, 2022

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 08, 2022