Date of Award

12-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Advisor

Keinath, Anthony

Committee Member

Agudelo, Paula

Committee Member

Zehnder, Geoffrey

Abstract

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum , was first described in 1894 in South Carolina and Georgia and has become a limiting factor in watermelon production worldwide. In recent years, restriction on use of the soil fumigant methyl bromide and the recent development of more virulent races of Fusarium oxysporum f. sp. niveum has created a critical need for alternative management techniques. In 2011-2013 field experiments were designed to evaluate the efficacy of incorporating a cover crop of hairy vetch into the soil to manage Fusarium wilt. Colony-forming units (CFU) of Fusarium oxysporum were sampled to evaluate differences among treatments as well as changes within a treatment over time. The incorporation of hairy vetch significantly increased CFUs of F. oxysporum from the baseline January sampling to the April sampling, post-incorporation of cover crops. The fumigants dimethyl disulfide + chloropicrin and methyl bromide + chloropicrin significantly reduced CFUs from the baseline sampling. Weekly disease ratings, percentage area covered by vines, and harvest data were collected and analyzed to see if the incorporation of hairy vetch reduced Fusarium wilt. In both 2012 and 2013, neither hairy vetch nor dimethyl disulfide + chloropicrin reduced disease incidence or increased yield when compared to the rye control. Separate field experiments were designed to compare the efficacy of grafting, soil fumigation, and a race 1-resistant cultivar on Fusarium wilt management. 'Tri-X 313', a susceptible cultivar, was grafted onto Emphasis ( Lagenaria siceraria ) and Strong Tosa (C. maxima X C. moschata ) rootstocks. 'Fascination' was used as the race 1-resistant cultivar, and dimethyl disulfide + chloropicrin was chosen as the fumigant. Disease incidence was assessed as in the cover crop study. The fumigant significantly lowered CFUs when compared to the rye control. In 2013, both rootstocks as well as the fumigant significantly reduced disease incidence when compared to the non-and self-grafted controls. 'Fascination' had a consistent disease rating of 15-20% in both years and had statistically lower disease than the non-grafted control in 2013. There were no differences in yield in any year among any treatments. It can be concluded from this two-year study that grafting was the best technique for Fusarium wilt management.

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