Aphid Alert 1999, No. 12, September 2

Summer 1999: Aphid trapping data.

Results reported in this issue of Aphid Alert are total captures of winged aphids and species identifications for the following locations and sampling interval end-dates. At some locations the potato crop has been harvested. If additional data is received for locations not reported on this page (no data) that data be incorporated into this week's issue of the newsletter once the samples have been received and sorted.

In addition to our summary of this weeks results we report results from our Aphid Alert subscriber survey and present an guest report by Debbie McLaren, Crop Production Pathologist with Agriculture and Agri-Food Canada, on aphid monitoring in Manitoba.

Figure 1 (below). Mean number of winged green peach aphid captured per trap across all locations reported, 1998 data (blue line) and 1999 data (maroon line). These data are also available in table format (Table 1).

graph showing captures of winged green peach aphids per trap from 1992-1994, 1998, and 1999 year to date

Figure 2 (below). Mean number of winged aphids of species known to be capable of transmitting PVY (exclusive of green peach aphid) captured per trap across all locations reported, 1998 data (blue line) and 1999 data (maroon line). These data are also available in table format (Table 1).

graph showing captures of PVY vectors other than green peach aphids per trap from 1992-1994, 1998, and 1999 year to date

Summary of Observations for Week Ending 2 September

Green peach aphids per trap declined from 3.19 per trap last week to 2.44 per trap this week. This is the first time this summer that green peach aphid captures per trap were less than in the corresponding week of 1998. Captures of other potential PVY vectors increased slightly, from 8.50 per trap last week to 11.73 this week. Turnip aphid has consistently been the most abundant of the potential PVY vectors. Turnip aphid is not as efficient a vector of PVY as is the green peach aphid, but it is a capable PVY vector and, therefore, cause for some concern. Like green peach aphid, we have found turnip aphid to be abundant this year on canola.

All winged green peach aphids captured in traps of the Aphid Alert network to this year (18 June through 25 August) have tested negative for potato leafroll virus and potato virus Y. Last week, 272 green peach aphids were tested and all were negative (Table 2).

Table 2

Location End date
for collection
Number of green
peach aphids tested
Baker 23-Aug 14
Cando 20-Aug 2
Climax 25-Aug 13
Gully 23-Aug 5
Hoople 20-Aug 65
Hollandale 11-Aug 1
Hollandale 18-Aug 1
Karlstad 25-Aug 22
Little Falls 17-Aug 2
Little Falls 23-Aug 3
Linton 15-Aug 10
Linton 23-Aug 6
Mandan 23-Aug 18
Morris 23-Aug 9
Rolette 20-Aug 7
Walhalla 20-Aug 43
Walhalla 12-Aug 51
Total   272

These results have surprised us, but are encouraging. These results suggest that, at most, a very small percentage of the winged green peach aphids migrating to potato prior to 25 August were infected with PVY or PLRV. Last summer, the first PLRV-positive green peach aphids were collected 14 July. In August of 1998, 59% of the winged green peach aphids captured in our traps tested positive for PLRV and in September, 86%. Results of the PCR testing of green peach aphids captured this past week will be reported next week.

The absence of any positives for either PLRV or PVY in the aphids collected this year is consistent with our interpretation that these are migrants moving into the potato crop from hosts other than potato.

As noted last week, winged aphids are now being produced in potato fields (i.e., the immature stages on potato are developing winged pads and will be able to fly as adults). Aphids developing on potatoes are much more likely to acquire and transmit potato viruses. Much current season transmission has already occurred. We believe that to date this has mostly been secondary transmission, i.e., within field transmission from plants grown from infected tubers.

Aphid Alert Subscriber Survey

Last week we mailed a survey to Aphid Alert subscribers. The survey was mailed to 123 who receive Aphid Alert by U.S. mail and to 78 who receive the Aphid Alert by e-mail. There is some overlap of these two lists and some recipients are not directly involved in the potato industry. To date, we have received 48 responses (we consider that a very impressive return), 19 by e-mail, 29 by U.S. Mail. Responses were received from 28 growers and 6 consultants. Here is what you had to say. Thirty seven said that you find Aphid Alert "very useful", 34 said that you read it "cover to cover", and 29 said that you use the information presented to "aid in management decisions." We are somewhat awed by the credibility (and responsibility) we appear to have, but we sincerely thank you for the huge vote of confidence and for having taken the time to complete this survey.

Detection of Potato Viruses in Manitoba

by D. L. McLaren
Crop Production Pathologist
Agriculture and Agri-Food Canada
Brandon Research Centre
P.O. Box 1000A
Brandon, MB R7A 5Y3 

The potato virology project was initiated in 1998 as a collaborative study involving Agriculture and Agri-Food Canada, Manitoba Agriculture, Manitoba Crop Diversification Centre, a number of industry partners and a number of commercial and seed potato growers. In 1998, 34 seed potato fields were surveyed for potato leaf roll virus and potato virus Y. This preliminary survey included a visual assessment of the field and evaluation of leaf and tuber samples. Virus levels in the leaf tissue were low but levels in the tubers were higher as was expected due to the influx of aphids occurring in August. In 1999, the study was expanded to include both commercial and seed potato fields to determine the presence and prevalence of these viruses, to evaluate the spread of viruses from different sources and to monitor aphid movement and detect the presence of aphids carrying virus.

In 1999, five suctions traps as well as 30 pan traps were located throughout potato production areas of Manitoba. A number of traps have been set up in a "cluster" which involve both seed potato fields and commercial fields. Fields are being monitored using traps, or have been assessed visually in areas including Shilo, Portage, Winkler, Holland, Carberry, Carman and Minto. Leaf samples are being collected from all fields where traps are located. Tubers will be collected from all 35 fields and assessed for viral infection. 

Webmasters note: next summer we plan to coordinate our activities and reporting with those of our Canadian colleagues to make this a truly regional, and indeed international project.

We maintain a list of e-mail addresses to facilitate communication with those of you interested in receiving updates about this research or any resulting advisories sooner than this information can be delivered by mail or even before it is posted on the WWW. If you wish your name added to receive such messages please send us an e-mail at radcl001@umn.edu. In the message, write "Aphid Alert subscribe."

Errors: If you find errors, typographic or factual, we would appreciate having them called to our attention so they can be corrected. Phone: Robert Suranyi (218) 773-3346 or Ted Radcliffe (612) 624-773 or send an e-mail to radcl001@umn.edu.

 

Results

Minnesota: Baker, Climax, Gully, Hollandale, Karlstad, Little Falls, Morris, Williams
North Dakota: Cando, Hoople, Linton, Mandan, Rolette, Walhalla

Baker, MN, week ending 30 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 11 44
  potato aphid
   
PVY vectors bird cherry-oat aphid 3 12
  corn leaf aphid 3 12
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid
  turnip aphid 3 12
   
Identified non-vector species   1 4
   
Unidentified   4 16
   
  Total 25

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Climax, MN, week ending 30 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 2 10
  potato aphid
   
PVY vectors bird cherry-oat aphid
  corn leaf aphid 12 60
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid 1 5
  turnip aphid
   
Identified non-vector species  
   
Unidentified   5 25
   
  Total 20

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Gully, MN, week ending 2 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 2 6.7
  potato aphid 1 3.3
   
PVY vectors bird cherry-oat aphid 5 16.7
  corn leaf aphid 14 46.7
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid
  turnip aphid 1 3.3
   
Identified non-vector species  
   
Unidentified   7 23.3
   
  Total 30

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Hollandale, MN, week ending 1 September

Data not available

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Karlstad, MN, week ending 31 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 2 10.5
  potato aphid
   
PVY vectors bird cherry-oat aphid 3 15.8
  corn leaf aphid 7 36.8
  English grain aphid 2 10.5
  greenbug
  sunflower aphid 1 5.3
  thistle aphid 1 5.3
  turnip aphid 2 10.5
   
Identified non-vector species  
   
Unidentified   1 5.3
   
  Total 19

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Little Falls, MN, week ending 30 August

Data not available

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Morris, MN, week ending

Data not available

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Williams, MN, week ending 31 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 5 8.5
  potato aphid 1 1.7
   
PVY vectors bird cherry-oat aphid 6 10.2
  corn leaf aphid 26 44.1
  English grain aphid 2 3.4
  greenbug
  sunflower aphid
  thistle aphid 5 8.5
  turnip aphid 9 15.3
   
Identified non-vector species  
   
Unidentified   5 8.5
   
  Total 59

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Cando, ND, week ending 27 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 6 27.3
  potato aphid
   
PVY vectors bird cherry-oat aphid 2 9.1
  corn leaf aphid 1 4.5
  English grain aphid 5 22.7
  greenbug
  sunflower aphid
  thistle aphid 1 4.5
  turnip aphid 7 31.8
   
Identified non-vector species  
   
Unidentified  
   
  Total 22

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Hoople, ND, week ending 27 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 59 44
  potato aphid 9 6.7
   
PVY vectors bird cherry-oat aphid 2 1.5
  corn leaf aphid 23 17.2
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid 6 4.4
  turnip aphid 32 23.9
   
Identified non-vector species  
   
Unidentified   3 2.2
   
  Total 134

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Linton, ND, week ending 29 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid
  potato aphid
   
PVY vectors bird cherry-oat aphid
  corn leaf aphid 11 50
  English grain aphid
  greenbug
  sunflower aphid 3 13.6
  thistle aphid
  turnip aphid 2 9.1
   
Identified non-vector species  
   
Unidentified   6 27.3
   
  Total 22

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Mandan, ND, week ending 29 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 2 6.7
  potato aphid 1 3.3
   
PVY vectors bird cherry-oat aphid 3 10
  corn leaf aphid 8 26.7
  English grain aphid 3 10
  greenbug
  sunflower aphid 1 3.3
  thistle aphid 1 3.3
  turnip aphid 7 23.3
   
Identified non-vector species  
   
Unidentified   4 13.3
   
  Total 30

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Rolette, week ending 27 August

  Aphid species # captured * % of total capture
PLRV/PVY vectors green peach aphid 2 (9) 9.4
  potato aphid   
                
PVY vectors bird cherry-oat aphid      
  corn leaf aphid         
  English grain aphid
  greenbug   
  sunflower aphid
  thistle aphid
  turnip aphid 56 (252) 87.5
               
Identified non-vector species   6 (27) 9.4
         
Unidentified  
         
  Total 64/288   

*Actual numbers in sorted subsample (projected numbers in total collection)

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Walhalla, ND, week ending 27 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 14 14.7
  potato aphid
        
PVY vectors bird cherry-oat aphid 1 1.1
  corn leaf aphid 8 8.4
  English grain aphid 3 3.2
  greenbug             
  sunflower aphid
  thistle aphid 13 13.7
  turnip aphid 55 57.9
         
Identified non-vector species  
             
Unidentified   1 1.1
             
  Total 95

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