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Plant & Soil Sciences
Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
In the Northeast, powdery mildew (PM), caused by Uncinula necator (Schewein.) Burrill is one of the most important grape diseases in terms of economic loss. It has been established that cultural practices, including proper sanitation, are the first step in preventing disease, and fungicide sprays are regularly applied to manage the disease. Currently, fungicides that successfully control PM have a strong potential to develop pathogen resistance, and alternatives with low risk of initiating resistance are not as effective in disease control. Our approach to this emerging resistance dilemma is to combine a systemic acquired resistance inducer (salicylic acid and potassium phosphate) with a topical fungicide, potassium bicarbonate. To determine each treatment’s level of efficacy, multiple aspects of infection and defense were quantified and qualified, including germination rate, lethality, lignin formation, callose formation, and vine and leaf growth. The first trial showed potassium bicarbonate and the standard fungicide (Pristine) inhibited the most germination and was most lethal against PM conidia. Potassium phosphate had little effect on germination and conidia death, and when combined with bicarbonate there was no different than the water control. In the second trial, the biorational mixture was able to reduce the level of powdery mildew infection significantly more than the other compounds, including the commercial standard. The salicylic acid and potassium bicarbonate mix may be successful enough to use in the vineyard to determine if the compound can tolerate field conditions with the same level of efficacy.
Daniel R. Cooley