Aphid Alert 2001, No. 2, June 29

Aphid Flight Activity during week ending 29 June

Aphid numbers were low at all locations reported. Potato aphid were captured at several locations. Potato aphid overwinters in the Northern Great Plains and generally is the most common potato colonizing aphid and virus vector found in potato during the early growing season. Some cereal aphids, e.g., bird cherry-oat aphid and corn leaf aphid were found. No green peach aphid were captured.

Trap locations for which data were not available when this page was created will be updated as results are received.

Aphid Captures, week ending 29 June. One suction trap and two pan traps are operated at each location, except Crookston , Rosemount and Thief River Falls. Data are reported as total aphid captures per three traps.

table showing Minnesota aphid capture data for the week ending June 29, 2001, cities A-J

table showing Minnesota aphid capture data for the week ending June 29, 2001, cities K-Z

table showing North Dakota aphid capture data for the week ending June 29, 2001

table showing Wisconsin, South Dakota, and Nebraska aphid capture data for the week ending June 29, 2001

2001 Late Blight Advisories for the Northern Great Plains

North Dakota, Minnesota, Wisconsin

Status of soybean aphid

by David Ragsdale, Professor of Entomology, University of Minnesota

An exotic aphid, the Asian soybean aphid, Aphis glycines Matsumura, has been found in six counties in Minnesota this spring (Houston, Ohlmsted, Wabasha, Goodhue, Winona, and Dakota). This aphid was first reported in North America last summer. However, the aphid appears to have been here for a few years as it was found in 10 North Central states last year. In 2001 the aphid has been found in Minnesota, Wisconsin, Iowa, Michigan, and Illinois. In Minnesota, the counties listed above defines the eastern edge of the aphid infestation and represents areas of the state where the soybean aphid likely overwintered.

As with most aphids, the overwintering host is a shrub or tree species. The soybean aphid has been confirmed overwintering on buckthorn, Rhamnus cathartica, in Illinois. Although we searched buckthorn in Minnesota, we were unable to find this aphid on buckthorn, but the pattern of aphids colonizing soybean this spring suggests local movement rather than long distance movement. For example, field edges near woodlots containing buckthorn is where soybean aphids could be found, while open fields without wooded edges were lacking aphids.

Soybean aphid is colonizing very young plants in the two leaf stage. We did observe field where heavy thunderstorms occurred when soybeans were in the two leaf stage and where aphids were found on 20% of the plants, have aphids almost wiped out following a 1.5" rain storm. Soybean aphids colonize the growing point of the plant and are somewhat exposed to the elements.

We are continuing to survey for soybean aphids and in collaboration with the MDA pest survey crew we will be sampling soybean fields in counties west of the Mississippi river this next week. We hope to devine the western edge of the soybean aphid distribution.

I think within a week or so aphids on some of the most heavily infested fields may begin to form winged individuals which may migrate out from these early colonized fields. Winged aphids (summer migrants) have been observed in Michigan this week with one field reported to have 22% of aphids developing wing pads.

Three entomologists (Dr. David Ragsdale, Dr. George Heimpel and Dr. Zhishan Wu) will be traveling to China, the native home of the soybean aphid, to search for parasites of the soybean aphid. Their goal is to release parasites of the soybean aphid that can control this exotic aphid alleviating the need for soybean producers to control aphids on soybean.

Visit the following web sites to view up to date distribution maps.

Photograph: False chinch bug, Nysius raphanus, the surprise potato pest of 2001

photo of a false chinch bug

During this past week we received calls about potato vines damaged by an unfamiliar pest. In some fields, very high densities of adult false chinch bugs were present on the crop, with many adults crawling over the plants, and some "swarming" activity observed. Adults and nymphs have piercing-sucking mouthparts, and do not appear to leave any distinguishing marks on the foliage. However, leaves on infested plants, and especially on young plants, were turning brown and stems of potato have wilted because of the large amount of sap being withdrawn. As of June 25, over 700 ac of potato had been treated in Minnesota. In potato, the only products we recommend at this time is Thiodan (endosulfan) or Monitor (methamidophos), applied with ground equipment using high volumes (40 gal/acre). Initial attempts at using dimethoate and one pyrethroid (Baythroid) in potato did not provide adequate control.

For more information on false chinch bug visit the June 29 issue of the Minnesota Vegetable IPM Newsletter.