Eighty-one Trifolium ambiguum accessions, representing the germ plasm collection for that br omide t soil wa and wit species, and selected accessions of T. alpestre, T. hybridum, T. medium, T. pratense, and T. repens methyl bromide at 76.4 kg/ha and kept were evaluated in the field from 1981 through 1983 for overall vigor, persistence, yield, and covered with plastic for 48 hr. Threedays susceptibility to virus infections. Infections by bean yellow mosaic virus, clover yellow vein virus, before planting, disulfoton, fensulfothion, white clover mosaic virus, and red clover vein mosaic virus were common in many accessions. and benomyl were incorporated into the Accessions of T. ambiguum and T. medium were the least affected by virus infections and persisted soil at 1.1, 8.4, and 48.9 kg/ha, better than other species. Symptoms of virus infection appeared early and spread rapidly in respectively. Foliar sprays of triadimefon, accessions of T. hybridum, T. pratense, and T. repens and were associated with loss of vigor and applied monthly, and methoxychlor, death of most of the plants by 1983. T. alpestre accessions were only moderately affected by viruses malathion, and benomyl applied biweekly, but showed neither the rapid growth of T. hybridum, T. pratense, or T repens nor the persistence of were used throughout each growing T. ambiguum or T. medium. Several accessions of T. ambiguum compared favorably with season at 0.14, 3.4, and 0.51 kg/ha, developed cultivars of T. pratense after 2 yr of field exposure.respectively. Disulfoton was broadcast
