Aphid Alert 2000, No. 6, July 16

Update: Summary of virus vector situation through 18 July

Captures of winged aphids in the Aphid Alert network traps remained low during the week ending 18 July. Minnesota and North Dakota locations averaged less than 3 aphids of all species per trap and less than 0.1 green peach aphid per trap. Total aphids and green peach aphid were both about twice as abundant as they were in the previous week. Total aphid captures in the fifth week of 2000 are about 1/3 of that during the same week of 1998 and 1999 and green peach aphid captures are 1/2 that of 1998 and 1/7 that of 1999.

What are aphid populations going to do for the rest of the year? Yogi Berra observed that "Prediction is very hard, especially when it is about the future." Aphid populations are lower on cereals or canola than in 1998 and 1999. However, both crops are nearing maturity and this will cause the aphids that are there to fly. We expect an increase in aphid flight activity in the near future. There are also substantial populations of green peach aphids on wild mustard. The surface flooding that occurred in many areas drowned out much cropland permitting wild mustard and other weed hosts of green peach aphid, e.g., redroot pigweed to take over. Scouting for green peach aphid should be focused on the margins of potato fields since this is where initial colonization occurs.

Potato leafhoppers are again abundant in the Red River Valley. The adults are not abundant enough to cause direct injury, but potato fields should be scouted for the nymphs. We have shown that reduced rates (1/4X) of dimethoate or Asana will give excellent leafhopper control without flaring aphids. Aster leafhoppers are present at very high densities. Aster leafhopper does not colonize potato, but this species vectors aster yellows (the causal agent of "purple top") which has been associated with dark chips.

graph showing captures of winged green peach aphids per trap from 1992-1994 and 1998-2000

Captures of PVY vectors (other than green peach aphid) per trap, 1998-1999

 

Aphid captures reported by location for week ending 18 July

Minnesota

Minnesota Baker
17 July
Climax
18 July
Crookston
18 July
Gully
17 July
Hollandale
18 July
Karlstad
18 July
  Aphids per trap per week
Species PLRV/PVY vectors  
green peach aphid 1 (4.2) 1 (3.5)       1 (6.3)
potato aphid 1 (4.2)   1 (3.2) 1 (8.3) 1 (11.1) 3 (18.8)
  PVY vectors
bird cherry-oat aphid 4 (16.7) 4 (13.8) 2 (6.5) 3 (25.0) 2 (22.2) 2 (12.5)
corn leaf aphid            
English grain aphid 1 (4.2) 1 (3.5)     1 (11.1)  
greenbug   1 (3.5)        
sunflower aphid   1 (3.5)        
thistle aphid 7 (29.2) 4 (13.8) 10 (32.3) 1 (16.7)   2 (12.5)
turnip aphid 3 (12.5) 3 (10.3) 4 (12.9) 1 (8.3) 1 (11.1) 3 (18.8)
Other PVY vectors   3 (10.3) 1 (3.2)   1 (11.1)  
  Non-vectors and unidentified
non-vectors 5 (20.8) 9 (31.0) 8 (25.8) 5 (41.7) 2 (22.2) 2 (12.5)
unidentified 2 (8.3) 2 (6.9) 5 (16.1)   1 (11.1) 3 (18.8)
Totals 24 29 31 12 9 16

Minnesota

Minnesota Little Falls
18 July
Morris
18 July
Rice
No data
Rosemount
19 July
Thief River
18 July
Williams
18 July
  Aphids per trap per week
Aphid species PLRV/PVY vectors
green peach aphid            
potato aphid         2 (3.9) 1 (4.8)
  PVY vectors
bird cherry-oat aphid 4 (15.4)       7 (13.8) 1 (4.8)
corn leaf aphid            
English grain aphid 1 (3.9)       4 (7.8) 7 (33.3)
greenbug         1 (2.0)  
sunflower aphid            
thistle aphid         12 (23.5) 1 (4.8)
turnip aphid 4 (15.4)       16 (31.4) 1 (4.8)
Other PVY vectors 1 (3.9)         2 (9.5)
  Non-vectors and unidentified
non-vectors 4 (15.4)       6 (11.8) 5 (23.8)
unidentified 12 (46.2)       3 (5.9) 3 (14.3)
Totals 26   0 No data  51 21

North Dakota

North Dakota Cando
7 July
Hoople
7 July
Linton
18 July
Mandan
18 July
Minot
No data
Rolette
7 July
Walhalla
7 July
  Aphids per trap per week
Aphid species PLRV/PVY vectors
green peach aphid           4 (10.3)  
potato aphid 1 (20) 1 (5.3)         2 (10)
PVY vectors
bird cherry-oat aphid 1 (20) 6 (31.6)       1 (2.6)  
corn leaf aphid             1 (5)
English grain aphid              
greenbug              
sunflower aphid              
thistle aphid           1 (2.6) 1 (5)
turnip aphid   3 (15.8) 1 (100)        
other PVY vectors           3 (7.7) 4 (20)
Non-vectors and unidentified
non-vectors 1 (20) 5 (26.3)       28 (71.8) 9 (45)
unidentified 2 (40) 4 (21.1)       2 (5.1) 3 (15)
Totals 5 19 1 0 No data 39 20

Wisconsin

Wisconsin Antigo
19 June
Rhinelander
19 June
  Aphids per trap per week
Aphid species PLRV/PVY vectors
green peach aphid    
potato aphid    
  PVY vectors
bird cherry-oat aphid    
corn leaf aphid 2 (50)  
English grain aphid    
greenbug    
sunflower aphid    
thistle aphid    
turnip aphid    
other PVY vectors 2 (50)  
  Non-vectors and unidentified
non-vectors   1 (100)
unidentified    
Totals 4 1

South Dakota

South Dakota Watertown
10 July
  Aphids per trap per week
Aphid species PLRV/PVY vectors
green peach aphid  
potato aphid  
  PVY vectors
bird cherry-oat aphid 5 (100)
corn leaf aphid  
English grain aphid  
greenbug  
sunflower aphid  
thistle aphid  
turnip aphid  
other PVY vectors  
  Non-vectors and unidentified
non-vectors  
unidentified  
Totals 5

Nebraska

Nebraska Cody
  Aphids per trap per week
Aphid species PLRV/PVY vectors
green peach aphid  
potato aphid  
  PVY vectors
bird cherry-oat aphid  
corn leaf aphid 1 (100)
English grain aphid  
greenbug  
sunflower aphid  
thistle aphid  
turnip aphid  
other PVY vectors  
  Non-vectors and unidentified
non-vectors  
unidentified  
Totals 1