Alfalfa Blotch Leafminer Invasion Continues
W. D. Hutchison,
R. C. Venette, E. C. Burkness and D. B. Hogg*
Department of Entomology, University of Minnesota
1980 Folwell Ave., St. Paul, MN 55108
*Dept. of Entomology, University of Wisconsin-Madison
| The alfalfa blotch leafminer (ABL), Agromyza frontella (Rondani) (Diptera: Agromyzidae), was first introduced into North America in 1968, in Massachusetts. ABL was first detected in northern Minnesota in 1994, but may have arrived in 1991 when infested hay was imported from Thunder Bay Ontario. With the assistance of scientists, extension personnel and Department of Agriculture personnel in Minnesota and Wisconsin, we have now documented ABL in over 123 counties in N. Dakota, Minnesota, Wisconsin and Illinois (see map). In addition, ABL has also spread west throughout much of Manitoba. In most of North America, an introduced parasite, Dacnusa dryas (Nixon) (Hymenoptera: Braconidae), suppresses ABL populations well below economic levels. Unfortunately, D. dryas, to our knowledge was not established in the Thunder Bay area and we have not yet detected the parasite in Minnesota or Wisconsin. Since 1996, infestations have been most severe in central and northwest Minnesota and northwest Wisconsin. |  |
In 1997, a simple diffusion model was developed to forecast future ABL distribution patterns in the upper midwest. The model was developed based on two assumptions: a) ABL moves ca. 60 mi/year, and that the Thunder Bay Ontario site was the source of the infestation. Using this model, a forecast map was made available to Extension and Dept. of Agriculture personnel to assist their search for ABL in 1998. The map, as part of a color brochure providing diagnostic photographs and biology information, proved to be very useful throughout the year. With a only a few exceptions, the "leading edge" of the ABL distribution in ND, MN, WI and IL tracked well with model prediction. The only exception was the lack of ABL in northeastern IA, as predicted by the model. Research will continue in 1999 to document the movement of ABL, as well as conduct complementary work on biological control and other control options.
This page was constructed by Gail Kampmeier at gkamp[at]uiuc.edu
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