This Is AuburnElectronic Theses and Dissertations

Studies on Wheat Scab in Alabama




Subedi, Arjun

Type of Degree



Entomology and Plant Pathology


Wheat scab is one of the more destructive diseases of wheat in the US. In Alabama, scab was not considered a problem in the past; however, during recent years it has been reported in north Alabama. The overall goal of this study was to address the prevailing status and management of wheat scab in Alabama. The specific objectives were: 1) to evaluate the efficacy of fungicides in control of wheat scab and foliar diseases of wheat in Alabama; 2) to evaluate perithecial development by Gibberella zeae on wheat straw; and 3) to determine the distribution of wheat scab incidence across Alabama and collect and characterize Fusarium species associated with the disease. For the first objective, fungicide trials were conducted for two years at each of three locations. Fungicides were evaluated for controlling scab as well as foliar diseases of wheat, which were effective in reducing foliar diseases in the areas with relatively high disease pressure, and had a consistently positive effect in improving yield components. Concentration of the mycotoxin, deoxynivalenol (DON), was assayed for wheat samples in 2012, where only a few samples had detectable levels of DON. To address the second objective, wheat straw were incubated in different soils with varying levels of moisture and temperature. Incubated straw were later inoculated with G. zeae and observed for perithecial development. Results showed greater perithecial development on straw incubated in finer textured soils from Tennessee Valley (Decatur silt loam) or Plant Breeding Unit (Independence loamy fine sand) compared to a coarse soil from Headland (Dothan sandy loam). Fewer perithecia developed on straw incubated for longer durations and at higher soil moistures or at higher temperatures. Results infer that crop residues in soil under warmer conditions with more rainfall, as in south Alabama provide less support for scab inoculum than residues in cooler and drier conditions more common in north Alabama. For the third objective, random wheat fields across the state were inspected for the presence of scab. Greater scab incidence was frequently noted in north Alabama, while a low incidence of scab was noted in central and southwestern Alabama and no disease was found in southeastern AL. Morphological characterization of the isolates showed that the fungal species associated with wheat scab in Alabama is F. graminearum.