Essex soybean seedling colonization by Fusarium oxysporum and F. solani and disease severity studies were conducted using soil collected from areas in a field (P. Minor field, King and Queen County), which exhibited poor stands and growth of Essex soybean in 1986. Tests were conducted also with soil collected from a field (Holland field, Suffolk), which had no history of poor soybean emergence or growth. Population densities of F. oxysporum and F. solani in the P. Minor soil were significantly higher (P≤0.05) than that in the Holland soil. In P. Minor soil maintained at -0.01 MPa water potential, no significant differences were found in disease severity for 15, 20 and 25 C after 6 days. However, disease severity was significantly (P≤0.05) higher at 20 C than at 15 C or 25 C, 13 days after planting. F. oxysporum and F. so/ani were isolated from lesions on Essex cotyledons and hypocotyls at all three temperatures. Rhizoctonia so/ani was isolated with highest frequency from hypocotyl lesions at 25 C. Colonization of soybean plant parts by F. oxysporum and F. solani in P. Minor soil was studied by plating asymptomatic, sequential, 2-mm long tissue segments on Komada's selective medium. Tissue segments from cotyledons, yielded significantly (P≤0.05) more F. oxysporum than F. solani, 3 and 4 days after planting. Both fungi were recovered at high frequencies from hypocotyl segments although F. solani recovery was significantly (P≤0.05) higher than F. oxysporum after 4 days of planting. From root segments, F. solani isolation frequency was significantly higher (P≤0.05) than F. oxysporum after 4 days. In Holland soil, the colonization patterns of F. oxysporum and F. solani were similar but the frequencies were lower than for P. Minor soil. Of 102 representative F. oxysporum, F. solani and R. solani isolates tested, 40% gave disease severity ratings on Essex soybean that were significantly (P≤0.05) higher than for the control, using artificially infested, pasteurized P. Minor field soil. In greenhouse soil- temperature tanks, all Fusarium and Rhizoctonia isolates tested caused significant (P≤0.05) reductions in stem length and plant fresh weight after 13 days at 20 C in soil maintained at -0.01 MPa water potential. Disease severity ratings for all F. oxysporum and F. solani isolates were significantly (P≤0.05) higher than that for the control. All F. oxysporum, F. solani and R. solani isolates delayed emergence of seedlings, compared to the control, but final stands were affected only slightly. / M.S.

Virginia is a net deficit state in corn and soybeans. The purpose of this study is to determine when during the crop year this deficit occurs, the relationship among production, consumption, and storage to determine if storage is a limiting factor, and why Virginia does not increase its production of these grains to meet the needs of its livestock poultry industries. Three sectors are considered in the study. These are the livestock and poultry industries which are the consumers of corn and soybeans, the corn and soybean production sector, and the storage sector. Trends in livestock and poultry show that from the 1965-1969 period to the 1975-1979 period there have been increases in the number of animals consuming feed and, in most cases, decreases in per head consumption of feed. Changes in production show increases in both acreage harvested as well as yields per acre over the same period. The result of these changes is a decrease in the corn deficit and relatively little change in the soybean deficit. Storage capacity has also been increased. On a state-wide basis, storage is adequate to meet the needs of the producers; whereas, in some regions it proves restrictive. A study of the movement of corn and soybeans indicates the costs of shipping these grains within the state are, for the most part, more expensive than importing the needed quantities from the Mid-West. / Master of Science