Date of Award


Degree Name

MS in Agriculture - Crop Science


Horticulture and Crop Science


College of Agriculture, Food, and Environmental Sciences


Shashika Hewavitharana

Advisor Department

Horticulture and Crop Science

Advisor College

College of Agriculture, Food, and Environmental Sciences


Surveys of the four major soilborne pathogens of strawberry (Fusarium oxysporum f. sp. fragariae, Macrophomina phaseolina, Phytophthora spp., and Verticillium dahliae) to determine their relative prevalence were conducted in Watsonville-Salinas, CA in 2021 and in Santa Maria, CA in 2022. All four major pathogens were detected at relatively similar prevalence in Watsonville-Salinas, between 22% and 31% of sampled fields. In Santa Maria, M. phaseolina was far more prevalent at 52% of sampled fields, the other three falling between 14% and 17%. Additionally replicated greenhouse and field trials were conducted to evaluate the effects of wheat as a single season cover crop on Macrophomina root rot of strawberry and the soil microbiome. Greenhouse trials and the first year of the field trial are described here and demonstrate a lack of substantial disease mitigation or pathogen reduction in the soil following wheat growth compared to no-treatment control. Significant changes were seen in the soil microbiome following wheat growth, including the significant amplification of several bacterial species known to be antagonistic to plant-pathogenic fungi.