Resistance of Glandular-haired Medicago Species to Oviposition by Alfalfa Weevils ( Hypera postica ) 1

Abstract

We evaluated annual glandular-haired diploids ( Medicago blancheana Boiss., and M. disciformis DC.) and tetraploids ( M. rugosa Desr. and M. scutellata (L.) Mill.) for resistance to adult alfalfa weevils, Hypera postica (Gyllenhal) in growth chambers. In no-choice and free-choice tests, adult weevils reared on M. sativa L. laid fewer eggs in stems of M. blancheana, M. rugosa and M. scutellata than in stems of M. sativa . Similar results were obtained in no-choice tests when weevils were reared from eclosion on the test species ( M. blancheana, M. rugosa and M. sativa) . Stem size was not related to oviposition resistance in the annual species. Adults preferred M. sativa to the glandular-haired species for feeding; adults confined to the glandular-haired species preferred stems to leaves. In contrast, leaves were readily accepted when the adults were confined to M. sativa . In no-choice tests, total adult mortality at 45 days was 65, 20, and 5%, respectively, for M. rugosa, M. blancheana, and M. sativa .