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ISSUE 16   August 24, 2000

 

SOYBEAN APHID FOUND IN MIDWEST

    A new aphid pest feeding on soybeans has been found in the midwestern states of Michigan, Illinois, Wisconsin, and possibly Minnesota. Other states neighboring these are likely to have some aphids present as well. Entomologists from Michigan, Wisconsin and Illinois reported finding aphids in soybeans in late July and early August. Last week (August 15) it was confirmed that this aphid was the soybean aphid, Aphis glycines, an aphid native to Asia but never reported from the
United States. The closest unconfirmed detection of the aphid may be in St. Paul and Rosemont, MN which were found by Bill Hutchison, U of M entomologist, and Erik Burkness.

    The soybean aphid is yellow-green with black cornicles ("tail-pipes") and a pale colored cauda (tail projection). As with other aphids, the soybean aphid is small, about the size of a pinhead. Nymphs would be smaller.

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    Aphids suck fluid from plants. When infestations are great, infested leaves are wilted or curled. The aphids excrete honeydew, a sweet substance that accumulates on lower leaf surfaces and promotes the growth of sooty mold. Observations from Asia indicate that the aphid colonizes tender leaves and branches from seedling to blooming. Later, as the growing point slows, the aphids slow their reproduction rate and move down to the middle and lower part of the plant where they feed on the undersides of leaves. Entomologists from the states with infestations are reporting this same trend. In addition, the Asian reports indicate that towards the end of the season the colonies begin to rapidly increase in size, again. In Asia, these increases are followed by a migration to an overwintering, alternate host. Observations in the infested states will lead to a better understanding of what soybean aphid will do in the US.

    Though no detections have been made in North Dakota, yet, field inspections are encouraged to determine if they have moved this far west. A suggested protocol for scouting is to sample 15 plants per field with at least 40 paces between plants. Inspect the undersides of leaves in the top and middle of the plants, or the entire plant if you have time. Record the number of plants infested and the relative abundance of aphids:

    If you find aphids in soybeans, contact Phillip Glogoza at 701-231-7581 in North Dakota and Ken Ostlie, U of M extension entomologist, at 612-624-7436. Information needed is:

    It is reported that this aphid feeds specifically on soybean (plants in the Genus Glycine). It is not expected that this aphid would feed on dry bean varieties (Phaseolus spp.). There are other aphids that may be found on dry beans, specifically the Bean aphid, Aphis fabae. This aphid is blue-black in color. The bean aphid has not been a problem in North Dakota.

Useful Websites, for more updates and info, by state:

MICHIGAN: Article by Dr. Chris DiFonzo, MSU: "Aphids amuck: soybean aphids discovered in U.S." -
August 17, 2000.

http://www.msue.msu.edu/ipm/CAT00_field/FC08-17-00.htm

 

WISCONSIN: Article by Dr. John Wedberg, University of Wisconsin, August 17, 2000

http://ipcm.wisc.edu/wcm/00-22insect1.html

 

ILLINOIS: Article by Dr. Mike Gray at the University of Illinois, August 16, 2000

http://www.ag.uiuc.edu/cespubs/pest/articles/200020h.html

MINNESOTA: Article by Ken Ostlie and Bill Hutchison, U of M. New Soybean Pest Appears in the Midwest: Is It in Minnesota?? MN Vegetable IPM Newsletter Vol. 2, No. 15, August 18, 2000

http://www.vegedge.umn.edu/mnvegnew/vol2/818new.htm

FACT SHEET, Australia (Good photos and references)

http://www.agric.nsw.gov.au/Hort/ascu/insects/aglycin.htm

 

Phillip Glogoza
Extension Entomologist
pglogoza@ndsuext.nodak.edu


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