Insect pests and associated root pathogens of sainfoin in western USA

Abstract

Sainfoin, Onobrychis viciifolia, Scop., is a perennial forage legume that was introduced into North America as an alternative to alfalfa, Medicago sativa L. Sainfoin does not cause bloating in livestock, is comparatively drought-resistant, and is not attacked by several economically important alfalfa insect pests. Plant survival in long-term sainfoin fields is reduced by root pathogens that invade through scars caused by root-feeding insects. Sitona scissifrons Say (Coleoptera: Curculionidae) weevils feed in sainfoin foliage and their larvae attack roots. Weevil populations were suppressed by application of carbofuran for two years in a newly established field. During the third year, there were fewer feeding scars and a lower incidence of tap-root disease in treated plots, indicating larval activity was associated with incidence of disease. In a seven-year trial near Bozeman, MT, alfalfa weevils. Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), and pea aphids, Acrythosiphon pisum (Harris) (Homoptera: Aphididae) attacked alfalfa but not sainfoin. Both crops were attacked by S. scissifrons, however, as well as by a complex group of plant bugs, including Lygus elisus VanDuzee, L. hesperus Knight, and Adelphocoris lineolatus (Geoze) (Hemiptera: Miridae). A seed-infesting insect, Bruchophagous spp. (Coleoptera: Curculionidae), was found in only sainfoin.