Trichomes and Field Resistance of Medicago Species to the Alfalfa Seed Chalcid (Hymenoptera: Eurytomidae) 1

We evaluated perennial Medicago species in the field to determine the effect of seed pod trichomes on resistance to the alfalfa seed chalcid, Bruchophagus roddi (Gussakovsky). Simple hairs were evaluated on M. sativa L., and glandular hairs on M. sativa L. subsp. praefalcata (Sinskaya) C.R. Gunn and M. glandulosa David. Simple hairs did not affect seed chalcid infestations. Density and length of erect glandular hairs on the seed pods were negatively correlated with seed chalcid infestations. No infested seeds were found on an M. glandulosa clone that contained long glandular hairs densely distributed on the seed pods.