FIRST REPORT OF THE ALFALFA BLOTCH LEAFMINER (DIPTERA, AGROMYZIDAE), AND SELECTED PARASITES (HYMENOPTERA, EULOPHIDAE) IN MINNESOTA AND WISCONSIN, USA

Alfalfa blotch leafminer, Agromyza frontella, has been a serious pest of alfalfa, Medicago sativa, in the northeastern U.S. and in eastern O ntario, Canada. Until recently, the western edge of the A. frontella d istribution in the U.S. was limited to eastern Ohio. We document for t he first time, the occurrence of A. frontella in Minnesota and Wiscons in. Alfalfa stems damaged by A. frontella, based on adult feeding punc tures, obvious blotched leafmining or the presence of larvae were firs t found in 3 northern Minnesota counties during October, 1994. Investe d counties included Lake of the Woods, Cook and Lake, all bordering we stern Ontario, Canada. In 1995, A. frontella was again found in Cook a nd Lake counties, where 99-100% of the stems, and 18-35% of the trifol iates/stem, contained larvae or exhibited obvious feeding damage. In 1 996, following a more expanded survey, a total of 11 and 5 counties, i n Minnesota and Wisconsin, respectively, showed some level of A. front ella feeding damage (stem samples ranged from <5 to 100% infested). Ba sed on additional counties surveyed 11 October, 1996, where A. frontel la was not found, we now have a reasonable estimate of the southern ed ge of the distribution in Minnesota and Wisconsin. A total of 2 and 6 A. frontella adults were identified from sweep-net samples taken from fields with obvious feeding damage during 1995 (Lake Co.) and 1996 (Co ok Co.), respectively. Three eulophid (Hymenoptera) parasites were rea red from A. frontella-infested alfalfa stems collected during October, 1994 in Cook Co., Minn., including: Diglyphus begini, D. pulchripes, and Diglyphus sp., prob. isaea, all of which are new records. Our hypo thesis is that A. frontella moved into Minnesota from Ontario Canada, via alfalfa hay purchased by northern Minnesota growers.