Aphid Alert 1999, No. 9, August 11

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.

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 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). Summary of observations for week ending 8 August.

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

Captures of winged green peach aphids per trap increased sharply during the week ending 8 August. Indeed, captures of green peach per trap this past week were considerably higher than during any week of 1998. Captures of other aphid species known to be potential vectors of PVY appear to have declined somewhat from levels recorded during the week ending 3 August and are well belows population levels on the same date last year.

During this past week, we have observed winged green peach aphids to be much more abundant on plants near the margins of potato fields than in the interior. This suggests that these aphids originated from outside the potato field. It is known that green peach aphid uses the visual contrast between foliage and bare soil to orient to potential host plants when terminating a "long distance" flight. The biological benefit to aphids of producing winged individuals is that this permits them to deposit their progeny in a new habitat where they may be more likely prosper. Aphids are more physiologically attuned to develop winged forms when their present host plant declines or otherwise becomes less suitable. The winged aphids we observed in the potato canopy this past week were giving birth to young. This suggests that they were recent arrivals rather than aphids about to disperse. That is further evidence that they are indeed recent invaders rather than aphids produced in the potato crop. The final evidence that these winged aphids are invaders is that few if the immature aphids in the potato field are developing wing pads (i.e., these are not destined to become winged adults).

This evidence all suggests that our traps are indeed capturing winged aphids as they move into the field rather than locally produced aphids. This is what we want to happen because it means that the results would be of greater predicitive value in forecasting risk of virus spread. Unfortunately, the aphid news is not good. We believe that the risk of virus spread is presently very high and probably will continue to be very high for the next couple of weeks.

The results of PCR tests to determine if the green peach aphids captured this week were carrying PLRV or PVY will not be reported on this web page until Friday of next week, our webmaster is traveling. However, state seed inspectors in both Minnesota and North Dakota are reporting "top infection", i.e., current season spread, so clearly potato viruses are being spread.

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 8 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 13 (15) 11.9
  potato aphid
   
PVY vectors bird cherry-oat aphid 4 (5) 3.7
  corn leaf aphid 1 (1) 0.9
  English grain aphid 1 (1) 0.9
  greenbug
  sunflower aphid 9 (10) 8.3
  thistle aphid 3 (3) 2.8
  turnip aphid 51 (59) 46.8
   
Identified non-vector species   10 (12) 9.2
   
Unidentified   17 (20) 15.6
   
  Total 109/127*

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Climax, MN, week ending 8 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 14 13
  potato aphid
   
PVY vectors bird cherry-oat aphid 5 4.6
  corn leaf aphid 1 0.9
  English grain aphid 1 0.9
  greenbug
  sunflower aphid 3 2.8
  thistle aphid 9 8.3
  turnip aphid 59 54.6
   
Identified non-vector species   3 2.8
   
Unidentified   13 12
   
  Total 108

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Gully, MN, week ending 8 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 5 17.2
  potato aphid
   
PVY vectors bird cherry-oat aphid 1 3.4
  corn leaf aphid 1 3.4
  English grain aphid
  greenbug
  sunflower aphid 6 20.7
  thistle aphid 1 3.4
  turnip aphid 4 13.8
   
Identified non-vector species   7 24.1
   
Unidentified   4 13.8
   
  Total 29

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Hollandale, MN, week ending 11 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 1 1.4
  potato aphid 1 1.4
   
PVY vectors bird cherry-oat aphid 1 1.4
  corn leaf aphid 48 68.6
  English grain aphid
  greenbug
  sunflower aphid   
  thistle aphid 1 1.4
  turnip aphid 4 5.7
   
Identified non-vector species   9 12.8
   
Unidentified   5 7.1
   
  Total 70

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Karlstad, MN, week ending 9 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 31 29.8
  potato aphid 1 1
   
PVY vectors bird cherry-oat aphid 5 4.8
  corn leaf aphid 4 3.8
  English grain aphid 1 1
  greenbug
  sunflower aphid 20 19.2
  thistle aphid 14 13.5
  turnip aphid 18 17.3
   
Identified non-vector species   2 2
   
Unidentified   8 7.7
   
  Total 104

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Little Falls, MN, week ending 9 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 8 11
  potato aphid
   
PVY vectors bird cherry-oat aphid 2 2.7
  corn leaf aphid 18 24.7
  English grain aphid 4 5.5
  greenbug
  sunflower aphid 12 16.4
  thistle aphid 1 1.4
  turnip aphid 12 16.4
   
Identified non-vector species   5 6.8
   
Unidentified   11 15.1
   
  Total 73

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Morris, MN, week ending 9 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 6 24
  potato aphid
   
PVY vectors bird cherry-oat aphid 1 4
  corn leaf aphid 2 8
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid 3 12
  turnip aphid 10 40
   
Identified non-vector species  
   
Unidentified   3 12
   
  Total 25

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Williams, MN, week ending 8 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 25 32.9
  potato aphid 3 3.9
   
PVY vectors bird cherry-oat aphid 4 5.3
  corn leaf aphid 1 1.3
  English grain aphid 1 1.3
  greenbug
  sunflower aphid 29 38.2
  thistle aphid 1 1.3
  turnip aphid 4 5.3
   
Identified non-vector species   2 2.6
   
Unidentified   6 7.9
   
  Total 76

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Cando, ND, week ending 5 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 1 3
  potato aphid
   
PVY vectors bird cherry-oat aphid 4 12.1
  corn leaf aphid 3 9.1
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid 3 9.1
  turnip aphid 18 54.5
   
Identified non-vector species  
   
Unidentified   4 12.1
   
  Total 33

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Hoople, ND, week ending 5 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 44 (48) 29.9
  potato aphid 5 (5) 3.4
   
PVY vectors bird cherry-oat aphid 11 (12) 7.5
  corn leaf aphid 1(1) 0.7
  English grain aphid
  greenbug 1 (1) 0.7
  sunflower aphid 1 (1) 0.7
  thistle aphid 8 (9) 5.4
  turnip aphid 55 (59) 37.4
   
Identified non-vector species   2 (2) 1.4
   
Unidentified   19 (21) 12.9
   
  Total 147/159

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Linton, ND, week ending 8 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 11 2.4
  potato aphid 1 0.2
   
PVY vectors bird cherry-oat aphid 1 0.2
  corn leaf aphid 29 6.3
  English grain aphid
  greenbug
  sunflower aphid 12 2.6
  thistle aphid 1 0.2
  turnip aphid 404 87.1
   
Identified non-vector species   1 0.2
   
Unidentified   4 0.9
   
  Total 464

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Mandan, ND, week ending 8 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 11 4.1
  potato aphid
   
PVY vectors bird cherry-oat aphid 1 0.4
  corn leaf aphid 10 3.7
  English grain aphid 1 0.4
  greenbug
  sunflower aphid 33 12.4
  thistle aphid 2 0.7
  turnip aphid 201 75.3
   
Identified non-vector species   2 0.8
   
Unidentified   6 2.2
   
  Total 267

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Rolette, week ending 5 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 2 9.1
  potato aphid 2 9.1
                
PVY vectors bird cherry-oat aphid 3 13.6
  corn leaf aphid         
  English grain aphid 1 4.5
  greenbug   
  sunflower aphid      
  thistle aphid 1 4.5
  turnip aphid 5 22.7
               
Identified non-vector species   3 13.6
         
Unidentified   5 22.7
         
  Total 22   

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Walhalla, ND, week ending 5 August

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 23 31.1
  potato aphid 3 4.1
             
PVY vectors bird cherry-oat aphid      
  corn leaf aphid         
  English grain aphid 1 1.1
  greenbug             
  sunflower aphid 1 1.4
  thistle aphid 5 6.8
  turnip aphid 26 35.1
         
Identified non-vector species   5 6.8
             
Unidentified   10 13.5
             
  Total 74

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