Aphid Alert

No. 7, posted
29 July, 1999

Published cooperatively by
departments of Entomology & Plant Pathology,
College of Agricultural, Food and Environmental Sciences,
University of Minnesota,
the University of Minnesota Extension Service,
and the State Seed Potato Programs of
Minnesota and North Dakota

Funding provided by:
1998 Minnesota State Legislature
& United States Department of Agriculture,
Cooperative State Research, Education and Extension Service,
Integrated Pest Management Program,
North Central Region

WWW address: <http://ipmworld.umn.edu/alert.htm>

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.

Baker, MN 26 Jul	Climax, MN 26 July	Gully, MN 26 July	Hollandale, MN 28 July
Karlstad, MN 27 July	Little Falls, MN 27 Jul	Morris, MN 26 July	Williams, MN 27 July
Cando, MN 23 July	Hoople, ND 23 July	Linton, ND 25 July	Mandan, ND 25 July
Rolette, ND 23 July	Walhalla, ND 22 July

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 27 Jul.

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 are establishing 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

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	5.0
	corn leaf aphid	27	33.8
	English grain aphid
	greenbug
	sunflower aphid	2	2.5
	thistle aphid	4	5.0
	turnip aphid	26	32.5

Identified non-vector species		3	3.8

Unidentified		10	12.5

	Total	80

Climax, MN, week ending 26 July
	Aphid species	# captured	% of total capture
PLRV/PVY vectors	green peach aphid	2	2.7
	potato aphid

PVY vectors	bird cherry-oat aphid	3	4.0
	corn leaf aphid	5	6.7
	English grain aphid	3	4.0
	greenbug
	sunflower aphid	27	36.0
	thistle aphid	9	12.0
	turnip aphid	17	22.7

Identified non-vector species		3	4.0

Unidentified		6	8.0

	Total	75

Gully, MN, week ending 26 July
	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	20.0
	thistle aphid	1	1.8
	turnip aphid	3	5.5

Identified non-vector species		8	14.6

Unidentified		7	12.7

	Total	55

Hollandale, MN, week ending 27 July
	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)

Karlstad, MN, week ending 27 July
	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

Little Falls, MN, week ending 26 July
	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

Morris, week ending 26 Jul
	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

Williams, MN, week ending 27 July
	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	38.0
	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

Cando, week ending 23 July
	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

Hoople, week ending 23 July
	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	13.0

Unidentified		17	22.1

	Total	77

Linton, ND, week ending 25 July
	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)	14.0

	Sorted/Total*	207/421
*Actual numbers in sorted subsample (projected numbers in total collection)

Mandan, ND, week ending 25 July
	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)

Rolette, week ending 23 July
	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

Walhalla, ND, week ending 22 July
	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	15.0
	turnip aphid	7	17.5

Identified non-vector species		4	10.0

Unidentified		4	10.0

	Total	40

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