Aphid Alert 1999, No. 13, September 8

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.

3 September 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). 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 September

Green peach aphids per trap averaged just 0.55 per trap during the week ending 8 September. Other aphids species which can vector PVY averaged 8.00 per trap. Thus, aphid numbers are lower than last week, and especially so for green peach aphid which was down 73%. Today, trap capture data is reported for only 9 of the 14 stations in the network. Missing data will be added to this WWW report as it becomes available and associated files will be updated accordingly. PCR data for green peach aphids captured during the week ending 2 September is also not yet available.

Last week, heavy rains were widespread. Some locations where we have traps received 3 or more inches of rain. Not only was the weather unfavorable for aphid flight, but some of the traps filled with water probably resulting in some loss of aphids that had been captured. Given the prevalence of late blight and the dire consequences of the wet weather, aphids probably were not the most immediate concern of most potato growers. However, the aphid and virus situation may be better than we earlier expected.

In early summer 1999, green peach numbers were considerably higher than on the same dates last year, but for the past two weeks numbers have been lower than last year. Over all dates, green peach aphid captures per trap are 49.4% higher than in 1998. Captures of PVY vectors other than green peach aphid are down 75.5% from 1998.

This summer, we have yet to detect our first PLRV-positive green peach, whereas last year 59% of green peach aphids captured in August 1998 were positive for PLRV. Our PCR tests have also been negative for PVY. PVY. However, IC-PCR data for PVY may less useful because PVY is non-persistent in the aphid, so non-detection only means that that aphid was not infected when captured. The data for PLRV is greater biological significance, because an aphid once infected with PLRV remains so for life.

Table 2. IC-PCR test results for week ending 30 August

Location End date
for collection
Number of
green peach aphids tested
Baker 30-Aug 11
Cando 30-Aug 2
Climax 25-Aug 13
Gully 2-Sep 61
Karlstad 31-Aug 2
Rolette 27-Aug 2
Walhalla 27-Aug 14
Williams 31-Aug 5
Total 102

Our most abundant potential PVY vector in 1999 has been turnip aphid, which reproduces on canola. A search of the literature has not provided much information as to the importance of this aphid as a PVY vector. This species is known to transmit PVY, but it appears that its efficiency as a vector is not established.

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 7 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid
  potato aphid
   
PVY vectors bird cherry-oat aphid 4 40
  corn leaf aphid 5 50
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid 1 10
  turnip aphid
   
Identified non-vector species  
   
Unidentified  
   
  Total 10

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Climax, MN, week ending 7 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid
  potato aphid
   
PVY vectors bird cherry-oat aphid 2 33.3
  corn leaf aphid 2 33.3
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid 1 16.7
  turnip aphid
   
Identified non-vector species   1 16.7
   
Unidentified  
   
  Total 6

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Gully, MN, week ending 7 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid
  potato aphid
   
PVY vectors bird cherry-oat aphid 1 1.3
  corn leaf aphid 76 96.2
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid
  turnip aphid
   
Identified non-vector species  
   
Unidentified   2 2.5
   
  Total 79

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Hollandale, MN, week ending 8 September

Data not available

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Karlstad, MN, week ending 8 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 1 100
  potato aphid    
       
PVY vectors bird cherry-oat aphid    
  corn leaf aphid    
  English grain aphid    
  greenbug    
  sunflower aphid    
  thistle aphid    
  turnip aphid    
       
Identified non-vector species      
       
Unidentified      
       
  Total 1  

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Little Falls, MN, week ending 8 September

Data not available

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Morris, MN, week ending 8 September

Data not available

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Williams, MN, week ending 6 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid
  potato aphid
   
PVY vectors bird cherry-oat aphid 14 31.8
  corn leaf aphid 27 61.4
  English grain aphid
  greenbug
  sunflower aphid
  thistle aphid
  turnip aphid
   
Identified non-vector species   1 2.3
   
Unidentified   2 4.5
   
  Total 44

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Cando, ND, week ending 3 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid
  potato aphid
   
PVY vectors bird cherry-oat aphid 11 50
  corn leaf aphid 1 4.5
  English grain aphid 2 9.1
  greenbug
  sunflower aphid
  thistle aphid 1 4.5
  turnip aphid 2 9.1
   
Identified non-vector species   1 4.5
   
Unidentified   4 18.2
   
  Total 22

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Hoople, ND, week ending 3 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 16 21.1
  potato aphid 14 18.4
   
PVY vectors bird cherry-oat aphid 6 7.9
  corn leaf aphid 28 36.8
  English grain aphid 1 1.3
  greenbug
  sunflower aphid
  thistle aphid 4 5.3
  turnip aphid 1 1.3
   
Identified non-vector species  
   
Unidentified   6 7.9
   
  Total 76

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Linton, ND, week ending 8 September

Data not available

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Mandan, ND, week ending 8 September

Data not available

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Rolette, week ending 3 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid
  potato aphid   
                
PVY vectors bird cherry-oat aphid    7    43.8
  corn leaf aphid         
  English grain aphid    1    6.3
  greenbug   
  sunflower aphid
  thistle aphid    1    6.3
  turnip aphid    1    6.3
               
Identified non-vector species      4   25.2
         
Unidentified      2    12.5
         
  Total 16   

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Walhalla, ND, week ending 3 September

  Aphid species # captured % of total capture
PLRV/PVY vectors green peach aphid 8 4.4
  potato aphid 1 0.6
        
PVY vectors bird cherry-oat aphid 2 1.1
  corn leaf aphid 12 6.7
  English grain aphid 2 1.1
  greenbug             
  sunflower aphid 4 2.2
  thistle aphid 122 67.8
  turnip aphid 3 1.7
         
Identified non-vector species   6 3.3
             
Unidentified   20 11.1
             
  Total 180

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