The effects of herbicides on axenic growth of Cylindrocladium crotalariae and on the development of CBR in the greenhouse and in the field was studied. In laboratory tests, dinitramine at 1, 5, and 10 ug/ml increased axenic growth of two isolates of C. Crotalariae in herbicide-amended potato-dextrose broth (PDB). Dinoseb and dinoseb + naptalam at the same rates also increased growth, whereas alachlor, benefin, diphenamid, vernolate and 2,4-DB were found to have no consistent effect. Treatment of infested soil with dinitramine at 1, 5, 10, 50, and 100 ug/g soil had no significant effects on populations of C. crotalariae microsclerotia (ms) in a Ruston or a Woodstown loamy fine sand. Dinoseb reduced ms populations significantly (P=0.5) in Woodstown soil at 5, 10, 50, and 100 ug/g soil and in Ruston soil at rates of 50 and 100 ug/g soil. In greenhouse tests, soil treatment with dinitramine at 0.56 kg/ha but not at 0.84 kg/ha increased significantly (P=0.05) the severity of CBR in Ruston and in Woodstown soil. In Ruston soil, dinitramine increased the severity of CBR only at an inoculum density of 5 ms/g soil, but in CBR only at an inoculum density of 5 ms/g soil, but in Woodstown soil, the herbicide resulted in disease increase only at 50 ms/g soil. Additional tests showed that disease severity was increased when peanut seedlings were pretreated with dinitramine and transplanted to herbicide-free infested soil. Dinitramine treatment was postulated to alter growth and development processes in ‘Florigiant’ peanut in a way to result in increased susceptibility to CBR. Dinitramine treatment of soil did not increase disease severity in ‘NC3033’ peanut, a CBR-resistant cultivar. Dinoseb at 1.68 kg/ha increased significantly (P=0.05) the severity of CBR in Woodstown soil, but did not in Ruston soil. Higher rates of dinoseb (3.36 and 6.72 kg/ha) were found to have no effect. Field tests were conducted in microplots (77-cm diameter) to determine the effects of herbicides on CBR. The severity of pod rot caused C. crotalariae was increased significantly (P = 0.05) by pre-plant soil treatment with dinitramine at 0.56 kg/ha, but not at 0.84 kg/ha in 1979. Although not significant (P=0.05), substantial increases in root rot and top symptom severity occurred in 1979 in response to this treatment. Pre-plant soil treatments with dinoseb at 1.68, 3.36, and 6.72 kg/ha did not affect disease development in microplots in 1979. In 1980, dinitramine (0.56 kg/ha) increased the severity of both root and pod rot significantly (P=0.05) in two separate microplot tests. Dinoseb at 1.68, but not at 3.36 or 6.72 kg/ha also increased significantly the severity of CBR in these tests.. Soil assay results indicated that herbicide treatments had no consistent effect on populations of C. crotalariae ms, .Macroposthonia ornatum or Meloidogyne hapla in microplots. These results provide evidence that certain herbicides can affect the development and severity of CBR in peanut. Furthermore, the present study emphasizes that knowledge of the non-target effects of pesticides on the biosphere can be significant and must be considered in tbs development of effective disease control programs. / Ph. D.