Evaluation of experimental populations and glandular-haired varieties of alfalfa for alfalfa blotch leafminer (Diptera: Agromyzidae) feeding injury

Following the spread of the alfalfa blotch leafminer, Agromyza frontella (Rondani) (Diptera: Agromyzidae), into Minnesota and Wisconsin U.S.A. during 1994-1997, three field trials were conducted in Minnesota to assess the potential for leafminer resistance among several sources of alfalfa (Medicago sativa), germplasm. In 1998, 86 entries were evaluated, most of which were experimental populations. In addition, six commercial varieties of alfalfa were evaluated. Of the six varieties, four had been bred for various levels of glandular-hair expression, specifically for resistance to the potato leafhopper, Empoasca fabae (Harris)(Homoptera: Cicadellidae). In two of three trials, we found no significant differences in leafmining injury to trifoliolates among the 86 entries, or among glandular-haired and traditional commercial varieties. At one location, 'Arrest,' 'Ameriguard 301,' and 'DK 121 HG' incurred significantly less pinhole injury than the glandular-haired variety '5347 LH' or the commercial standard, '5454.' However, after accounting for both pinhole and leafmining injury, only 'Arrest' and 'Ameriguard 301' had less injury than '5347 LH,' 'DK 121 HG,' or the standard '5454.' The low levels of resistance to A. frontella injury, among glandular-haired commercial alfalfa varieties and numerous experimental populations M. sativa, confirm the need for alternative A. frontella management strategies such as biological control and possible manipulation of harvest schedules.