Trap Catches to August 27, 2021.

As evening temperatures decrease and plant hosts start to senesce throughout the region, aphid numbers are dropping rapidly.  Overall catch across the trapping network is down 75% from last week and the average catch per trap is lower still.  There were very few aphids captured over all and the rise in the PVY Vector Risk Index is only 20% of what it was just last week.

Next week will likely be the last week of trapping, many trap sites have already stopped for the season as vine kill and/or harvest has already occurred.  Overall, the PVY risk looks considerably lower than this time in 2020; 2021 saw earlier flights but overall numbers of vectors were still lower.

Keep scouting, we'll keep counting...

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Cumulative PVY Vector Risk Index to Sept 10, 2021

Cumulative PVY Vector Risk Index to Sept 09, 2020 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending Sept 10, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to Sept 10, 2021 

 

Trap Catches to August 27, 2021.

Trap capture numbers remained very similar to last week's.  The numbers of both vectoring and non-vectoring aphids were almost the same.  While trap captures per trap were marginally higher than last week, overall numbers are low.  This meant only a small increase in the PVY Vector Risk Index.  As mentioned last week, the peak aphid flight obviously occurred early this year and so the risk from PVY vectors is lower than at this time last year (our current regional PVY Vector Risk Index is only ~41% of what it was last year).

The species composition is  little changed from last week, Cotton/Melon aphids are down, Soybean aphid numbers are up.  Buckthorn and cereal aphids remain relatively the same.  Overall, these numbers are promising as the season winds down.

Keep scouting, we'll keep counting...

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Cumulative PVY Vector Risk Index to Sept 03, 2021

Cumulative PVY Vector Risk Index to Aug 28, 2020 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending Sept 03, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to Sept 03, 2021 

 

Trap Catches to August 27, 2021.

The numbers of aphid captures per trap continues to decrease this week, but vector numbers overall remained similar to last week.  There was only a slight increase in the PVY Vector Risk Index, putting us well behind last year at this time.  In 2020, we were recovering large numbers of late-season aphids that vector PVY and Vector Risk Index numbers at Aug 28 last year were roughly twice what they are now.  The high temperatures early in the summer likely accelerated the development, and subsequent decrease in host quality of other aphid plant hosts.  This stimulated an earlier dispersal of aphids, including those that vector PVY.  However, those earlier moving populations means there are fewer vectors flying now, we already seem to be past peak vector numbers.

There were still numbers of certain aphid species moving.  Soybean aphids were recovered from several trap locations and there are still Corn Leaf aphids being recovered in many locations.  Non-vectoring species of aphids ticked up a small amount this week.

The high temperatures and lack of precipitation have meant that in some locations tuber set and size are less than desired.  As noted, while numbers are decreasing, there are still aphids present that can vector PVY.  If delaying vine kill to allow more time for bulking, keep aware of aphid numbers.  

 Keep scouting, we'll keep counting...

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Cumulative PVY Vector Risk Index to Aug 27, 2027

Cumulative PVY Vector Risk Index to Aug 28, 2020 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 27, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 27, 2021 

 

Trap Catches to August 20, 2021.

The numbers of aphid vector species decreased significantly this week.  The number of trap locations reporting decreased by 25%, but the number of vectors recovered decreased by 75%.    

The numbers of all vector species but Buckthorn aphids decreased this week, as did the number of non-vector  species.  The lower number of vectors resulted in only a small increase in the PVY Vector Risk Index.  

Our aphid population dynamics are very different from last year.  In 2020, a late season increase in vector numbers drove the PVY Risk higher.  It seems this year we are seeing an early decrease in vector numbers.  Compare the graphs below.  The first is the 12 regional year average weekly vector capture.  The second is the regional weekly vector capture to this point in 2021.  It remains to be seen if the pattern continues, but the high temperatures and drought this season may have driven both plant host and aphid populations along faster than in previous years.  Just a guess at this point...

Harvest is coming but the later varieties in areas that caught some moisture may still have a lot of green out there.  And that's just the color being sought by any vector still flying out there.

If It's Green, Then By Aphids It Can Be Seen!  

Yes, I know, that one's coming back to haunt me....  

 Keep scouting, we'll keep counting...

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Cumulative PVY Vector Risk Index to Aug 20, 2021

Cumulative PVY Vector Risk Index to Aug 21, 2020 (please note different scale) 

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 20, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 20, 2021 

 

Trap Catches to August 13, 2021.

Aphid vector numbers decreased again this week, although we did see the first Green Peach aphid of the year (but only 1 so far!).  Most species numbers were down over all.

Soybean and Corn Leaf aphids remained roughly the same while English Grain aphids were only half of last week's numbers.  A single Green Peach aphid was recovered from the Ada, MN site.  Numbers of other vector species were also down over all.  Non-vector aphid species decreased by 20% but there are still numerous aphids flying.  

While the season appears to be slowing, remember our peak aphid flights in Minnesota and North Dakota occur through August, explaining why most of our PVY is transmitted later in the season.  There's still a lot of time for aphids to find green plants, so continue appropriate disease management tactics.

Keep scouting, we'll keep counting...

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to Aug 13, 2021

Cumulative PVY Vector Risk Index to Aug 13, 2020 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 13, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 13, 2021 

 

Trap Catches to August 06, 2021.

Aphid numbers were down for the second week in a row.  Traps last week recovered approximately 120 fewer aphids across the region as compared to the previous week.  The majority of this decline was in non-vector and small grain aphid species.   

Only about 1/3 the number of English Grain aphids were recovered in traps in the past week, which is reflective of the amount of grain harvested over the past week or two.  Conversely, Corn Leaf aphids became the most numerous vector species captured this trapping period.  Again, perhaps reflective of the maturing corn in the region.  

The changing status of crop hosts is starting to be reflected in different aphid species being recovered in the suction traps.  Sunflower and Thistle aphids were present in several locations last week.  And both Soybean and Buckthorn aphid numbers ticked up last week as well.

Soybeans in many locations are becoming increasingly drought stressed but we have yet to encounter the low night temperatures which are linked to Soybean aphids returning to buckthorn.  Their increase last week may be more influenced by the typical late July / early August dispersal event we usually see.  

Aptly coined the SDE (Sturgis Dispersal Event) by Bruce Potter, our IPM Specialist at the Southwest Research & Outreach Center in Lamberton, this dispersal event seems to historically co-occur with the Sturgis Motorcycle Rally (which starts Aug 06 this year). Bruce first developed this hypothesis in response to some surprising photomicrographs he was able to obtain and share a few years back.  The orange and black coloring, strangely emblematic, on that particular Soybean aphid's thorax is certainly atypical for the species...  😉

As mentioned last week, much of the peak aphid flight in Minnesota and North Dakota seem to occur in August.  So we may yet have a lot of aphids moving between fields.  As long as there's green plant material, aphids will probe and PVY can be transmitted.  Most of our PVY is transmitted later in the season, so continue appropriate disease management tactics.

Keep scouting, we'll keep counting...

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to Aug 06, 2021

Cumulative PVY Vector Risk Index to Aug 09, 2020 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for the week ending Aug 06, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 06, 2021 

 

Trap Catches to July 30, 2021.

The aphid numbers decreased quite a bit this week - perhaps aphids don't like wood smoke!  The weather definitely had some effects on certain locations - apparently the Perham trap was blown over by powerful in-line winds - but our cooperators there got it set back up again.  

Unfortunately, the decrease in aphids was all in non PVY vectoring species (darn it!); the number of aphids that can vector PVY remain basically the same as last week.  There were, however, some small changes in what species were recovered.

English Grain aphids made up the vast majority of the vectors captured in suction traps.  Their continued presence probably reflects different planting dates for small grains this year.  There were slightly fewer Soybean aphids but they were recovered at several locations. Damson-hop and Cannabis aphids were both found in a couple of locations and Corn Leaf aphids are continuing to move as well.

The days are getting shorter but this is also the time of year when we typically have the greatest movement of aphid vectors and the greatest increase in risk of PVY transmission.  The graph below was calculated from our 12 years of Aphid Alert Trap data - it shows the average number of vectors recovered per trap by ISO-8601 week (a way of standardizing week numbers across all years).. 

Continued scouting is recommended, and use of crop oils and insecticides which stop feeding/probing may also prove necessary.  Remember, as long as there's green plant material, aphids will land and probe plants.  This means PVY can be vectored.  With the drought conditions and temperatures in several seed growing locations, care should be taken with oils to monitor for phytotoxicity.  

We will keep counting.  As always, keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 30, 2021

Cumulative PVY Vector Risk Index to July 31, 2020 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for the week ending July 30, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 30, 2021 

 

Trap Catches to July 23, 2021.

Aphid vector catch numbers jumped for the third week in a row.  Total trap catches totaled just over 800 aphids, about 25% of which (195 aphids) were species that can vector PVY.  These high capture numbers drove the PVY Vector Risk Index up again this week (by about 65%).  Most of the vectors captured (148 aphids) were English Grain aphids - more than twice the number of last week's catch of this species.  So the movement of grain aphids to potatoes continues to increase.  As small grains continue to mature and harvest begins, the number of grain aphids should decrease, but other vector species may rise.  Soybean aphid captures doubled over last week, Corn Leaf and Black Bean aphids increased, and we recorded our first Damson-Hop aphid of the summer.  

There were large captures of non-vectors this week, showing overall aphid activity was up.  What was interesting about the non-vector species is that the capture was comprised of less than 6 species, which included Spotted Alfalfa aphid (which has been reported from areas in southern MN and ND.     

With the increases in PVY vectors, continued scouting and use of crop oils is recommended, insecticides which stop feeding/probing may also prove necessary.  Although with the drought conditions and temperatures in several seed growing locations, care should be taken with oils to monitor for phytotoxicity.  

We will keep counting.  As always, keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 23, 2021

Cumulative PVY Vector Risk Index to July 24, 2020 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for the week ending July 23, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 23, 2021 

 

Trap Catches to July 16, 2021.

Aphid vector catch numbers took another jump this week.  Driven by greater numbers of Soybean aphid and large numbers of English Grain aphids being recovered from multiple reporting sites, the PVY Vector Risk increased again this week.  There are still no Green Peach aphids being captured at any site, in additional to increased numbers of Soybean and English Grain aphids, numbers of Buckthorn aphids were up this week as were several other vectors.  The first captures of Cannabis aphids occurred this past week and Potato aphids seem to be increasing slightly.  All in all, numbers are up driving the Vector Risk Index to a higher level than this time last year.

Continued scouting and use of crop oils is recommended.  Although with the drought conditions and temperatures in several seed growing locations, care should be taken with oils to monitor for phytotoxicity.  

We will keep counting.  As always, keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 16, 2021

Cumulative PVY Vector Risk Index to July 19, 2020 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for the week ending July 16, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 16, 2021 

 

Trap Catches to July 09, 2021.

Aphid vector catch numbers increased significantly this week with the PVY Vector Risk Index values doubling in the past 7 days.  Cereal aphids are dispersing from the senescing small grains; most trapping sites reporting in the past week captured English Grain Aphids, and many reported Corn Leaf or Bird-Cherry Oat aphids.  Soybean aphids have also started their summer dispersal flight with most sites recovering low numbers of this aphid.  Cotton/melon and Buckthorn aphids were also recovered at several sites this week.  

The weather conditions still favor aphid population development and we expect further cereal aphid flight over the next couple of weeks.  The most numerous species reported this week are non-colonizing species, they don't become established on potato but they do enter potato fields and probe plants to assess if they're suitable food sources.  This probing is sufficient to acquire virus particles on their mouthparts.  After they determine potatoes aren't a viable food host, these aphids will fly to another plant, relatively close by and probe that one.  Non-colonizing aphids will work their way across a field trying plants and moving on.  Consequently, they will spread any PVY inoculum in the field.  Unfortunately, because they don't form colonies on potato plants, they're unlikely to be spotted with standard scouting techniques.  But colonizing species are being recovered as well, so it's still important to keep up the field scouting.

Increasing flights of colonizing and non-colonizing aphid vectors in our traps are good indications that the risk of PVY spread is increasing in the region.  The use of refined crop oils may well be a good addition to management practices (see below).

We'll keep reporting numbers.  As always, keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 09, 2021

Cumulative PVY Vector Risk Index to July 10, 2020 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for the week ending July 09, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 09, 2021 

 

Trap Catches to July 02, 2021.

There have been high numbers of aphids in some traps this week, but the number of aphids that vector PVY remains relatively low (although a little ahead of last year but much lower than 2019).  The vast number of aphids recovered in traps up to July 02 have been non-vector species.  Consequently, the PVY Vector Risk Index values remain low to this point as well.

The weather conditions still favor aphid population development and small grains are starting to senesce early.  Several locations have reported late season aphids on wheat, as the grain dries, these populations will generate a winged generations that will disperse to the remaining green crops, like potatoes.  All of this means aphid populations will continue to rise.  

We'll keep reporting numbers.  As always, keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to July 02, 2021

Cumulative PVY Vector Risk Index to July 03, 2020 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for the week ending July 02, 2021

Cumulative Aphid Species Capture and PVY Vector Risk Index to July 02, 2021 

Trap Catches to June 25, 2021.

The season is off to a slow start.  This is a bit surprising given the warm, dry conditions would be expected to suppress some of the mortality factors that generally limit aphid populations.  We have recovered high numbers of non-vector aphid species in the past couple of weeks, but very few PVY vectors are flying.

Most sites have started their trapping and we are getting catch data from an increasing number of sites.  We should have most sites up and running by next week.   

I anticipate we might start to see cereal aphids dispersing from small grains earlier this year then normal.  The grain seems already to be drying and progressing quite rapidly.

We'll keep reporting numbers.  As always, keep on scouting!

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Cumulative PVY Vector Risk Index to June 25, 2021

Aphid Species Captured and PVY Risk Index for the week ending June 25, 2021