Aphid Alert 1999, No. 7, July 27

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. Data for missing locations will be incorporated into this week's issue of the newsletter as the data becomes available.

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).

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

Summary of observations for week ending 27 July

The number of green peach aphids captured in our traps has been consistently higher in 1999 than on comparable dates in 1998. To date, none of the green peach aphid captured tested positive for PVY or PLRV, but their high numbers are reason for concern. PVY vectors are presently at densities very similar to that experienced in 1999. However, aphid numbers are still far below the peak densities observed in 1998.

Will aphid populations follow the same trends in 1999 that they did in 1998? It is possible they may not. Previous observation, suggests that the aphid pressure we experienced in 1998 was exceptional, if not unprecedented. But, it may also be that the cropping systems and production practices now in place tend to favor aphids. In any event, given the large amount of inoculum present in the potato seed planted this year growers should monitor their fields closely.

Aphid populations are greatly influenced by weather and pesticide use patterns. Cool wet weather tends to favor green peach aphid (and probably most aphid species?). So the weather patterns we experience over the next month could be the telling factor. Unfortunately, the presence of tremendous numbers of leafhoppers necessitating repeated applications of insecticide and the routine application of late blight fungicides have worked against biological control. Still it is possible if we get a spell of hot dry weather, that green peach numbers could level out or even decline.

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 26 July

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 1 1.3
  potato aphid 4 3.8
       
PVY vectors bird cherry-oat aphid 4 5
  corn leaf aphid 27 33.8
  English grain aphid    
  greenbug    
  sunflower aphid 2 2.5
  thistle aphid 4 5
  turnip aphid 26 32.5
       
Identified non-vector species   3 3.8
       
Unidentified   10 12.5
       
  Total 80  

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Climax, MN, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 2 2.7
  potato aphid    
       
PVY vectors bird cherry-oat aphid 3 4
  corn leaf aphid 5 6.7
  English grain aphid 3 4
  greenbug    
  sunflower aphid 27 36
  thistle aphid 9 12
  turnip aphid 17 22.7
       
Identified non-vector species   3 4
       
Unidentified   6 8
       
  Total 75  

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Gully, MN, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 1 1.8
  potato aphid    
       
PVY vectors bird cherry-oat aphid 4 7.3
  corn leaf aphid 19 34.6
  English grain aphid 1 1.8
  greenbug    
  sunflower aphid 11 20
  thistle aphid 1 1.8
  turnip aphid 3 5.5
       
Identified non-vector species   8 14.6
       
Unidentified   7 12.7
       
  Total 55  

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Hollandale, MN, week ending

  Aphid species # captured * % of total capture
PLRV/PVY vectors green peach aphid    
  potato aphid 1 (2) 1.5
       
PVY vectors bird cherry-oat aphid 1 (2) 1.5
  corn leaf aphid 51 (89) 78.5
  English grain aphid    
  greenbug    
  sunflower aphid    
  thistle aphid 1 (2) 1.5
  turnip aphid 1 (2) 1.5
       
Identified non-vector species   1 (2) 1.5
       
Unidentified   9 (16) 13.8
       
  Sorted / Total * 65 / 114  

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

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Karlstad, MN, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 9 7.8
  potato aphid 3 2.6
       
PVY vectors bird cherry-oat aphid 3 2.6
  corn leaf aphid 2 1.7
  English grain aphid    
  greenbug    
  sunflower aphid 8 6.9
  thistle aphid 16 13.8
  turnip aphid 53 45.7
       
Identified non-vector species   2 1.7
       
Unidentified   20 17.2
       
  Total 48  

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Little Falls, MN, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid    
  potato aphid 3 4.8
       
PVY vectors bird cherry-oat aphid    
  corn leaf aphid 13 20.6
  English grain aphid 18 28.6
  greenbug    
  sunflower aphid 3 4.8
  thistle aphid 6 9.5
  turnip aphid    
       
Identified non-vector species   10 15.9
       
Unidentified   10 15.9
       
  Total 63  

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Morris, MN, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid    
  potato aphid 1 2.6
       
PVY vectors bird cherry-oat aphid    
  corn leaf aphid 11 28.2
  English grain aphid    
  greenbug    
  sunflower aphid    
  thistle aphid 14 35.9
  turnip aphid    
       
Identified non-vector species   2 5.1
       
Unidentified   11 28.2
       
  Total 39  

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Williams, MN, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 4 5.1
  potato aphid    
       
PVY vectors bird cherry-oat aphid 6 7.6
  corn leaf aphid 30 38
  English grain aphid 5 6.3
  greenbug    
  sunflower aphid 7 8.9
  thistle aphid 9 11.4
  turnip aphid 6 7.6
       
Identified non-vector species   3 3.8
       
Unidentified   9 11.4
       
  Total 79  

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Cando, ND, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 1 1.8
  potato aphid 3 5.5
       
PVY vectors bird cherry-oat aphid 12 21.8
  corn leaf aphid    
  English grain aphid 1 1.8
  greenbug    
  sunflower aphid    
  thistle aphid 5 9.1
  turnip aphid 25 45.5
       
Identified non-vector species   3 5.5
       
Unidentified   5 9.1
       
  Total 55  

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Hoople, ND, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 5 6.5
  potato aphid 5 6.5
       
PVY vectors bird cherry-oat aphid 4 5.2
  corn leaf aphid 3 3.9
  English grain aphid    
  greenbug 3 3.9
  sunflower aphid 1 1.3
  thistle aphid 4 5.2
  turnip aphid 25 32.5
       
Identified non-vector species   10 13
       
Unidentified   17 22.1
       
  Total 77  

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Linton, ND, week ending

  Aphid species # captured * % of total capture
PLRV/PVY vectors green peach aphid 4 (8) 1.9
  potato aphid 1 (2) 0.5
       
PVY vectors bird cherry-oat aphid 3 (6) 1.5
  corn leaf aphid 19 (39) 9.2
  English grain aphid    
  greenbug    
  sunflower aphid 3 (6) 1.5
  thistle aphid 6 (12) 2.9
  turnip aphid 128 (260) 61.8
       
Identified non-vector species   14 (28) 6.8
       
Unidentified   29 (60) 14
       
  Sorted / Total * 207 / 421  

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

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Mandan, ND, week ending

  Aphid species # captured * % of total capture
PLRV/PVY vectors green peach aphid 10 (20) 5.4
  potato aphid 6 (12) 3.2
       
PVY vectors bird cherry-oat aphid 5 (10) 2.7
  corn leaf aphid 3 (6) 1.5
  English grain aphid 17 (34) 9.1
  greenbug    
  sunflower aphid    
  thistle aphid 4 (8) 2.2
  turnip aphid 126 (252) 67.7
       
Identified non-vector species   8 (16) 4.3
       
Unidentified   7 (14) 3.8
       
  Sorted / Total * 186 / 370  

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

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Rolette, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 7 6.5
  potato aphid 3 2.8
       
PVY vectors bird cherry-oat aphid 6 5.6
  corn leaf aphid       
  English grain aphid 1 0.9
  greenbug    
  sunflower aphid    
  thistle aphid 4 3.7
  turnip aphid 79 73.2
         
Identified non-vector species   4 3.7
       
Unidentified   4 3.7
       
  Total 108  

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Walhalla, ND, week ending

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 3 7.5
  potato aphid 7 17.5
       
PVY vectors bird cherry-oat aphid 5 12.5
  corn leaf aphid    
  English grain aphid 1 2.5
  greenbug        
  sunflower aphid 3 7.5
  thistle aphid 6 15
  turnip aphid 7 17.5
        
Identified non-vector species   4 10
       
Unidentified   4 10
       
  Total 40  

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