|Miller Butler, Melinda
Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2016
Publication Date: 11/1/2017
Citation: Smith, B.J., Miller Butler, M.A. 2017. Effect of cultural practices and fungicide treatments on the severity of Phytophthora root rot of blueberries grown in Mississippi. Acta Horticulturae. 10.17660/ActaHortic.2017.1180.8.
Interpretive Summary: Phytophthora root rot is an important disease of blueberries, especially those grown in the southeastern United State on poorly drained soils. Management of this disease is based primarily of cultural practices. These trials compared the effectiveness of several cultural practices and fungicides for controlling root rot of two blueberry cultivars. Growing blueberries on raised beds, drenching the soil around plants, and treating plants with a foliar-applied fungicide resulted in more vigorous plants and less plant mortality compared to plants grown on flat beds or those that did not receive any fungicide treatment. These results will help blueberry growers manage this disease and should lead to higher production of better quality blueberries for the American consumer.
Technical Abstract: Phytophthora root rot is an important disease of blueberries, especially those grown in areas with poor drainage. Reliable cultural and chemical management strategies are needed for control of this disease. Two studies were conducted to evaluate the effects of cultural practices and fungicide treatments on plant vigor and mortality of blueberries planted in a Phytophthora cinnamomi infested soil. One-year-old ‘Star’ and two-year-old ‘Legacy’ plants were transplanted to flat or raised beds (whole plots) fertilized with 0.5x, 1x, or 2x levels of nitrogen as urea (subplots). Within subplot treatments were soil amendments (pine bark, peat, none), fungicide treatments (phosphorous acid foliar, fosetyl-Al foliar and drench, and mefenoxam drench), or a combination of fungicide (mefenoxam) and soil amendment (peat). Plant vigor was rated twice a year. ‘Star’ plants were grown for five years and ‘Legacy’ plants were grown for two years. At the conclusion of each study plants were harvested and their top and root dry weights were recorded. At each bi-yearly evaluation, ‘Star’ plants grown on raised beds were more vigorous than those grown on flat beds; however there were no significant differences in overall plant vigor or mortality due to nitrogen level. ‘Star’ plants in the phosphorous acid treatment consistently received high plant vigor ratings. After two years, ‘Legacy’ plants fertilized with the 2x nitrogen level had the highest vigor score, the greatest percentage of living plants, and the greatest top dry weight; plants in the fosetyl-Al foliar, phosphorous acid, and mefenoxam treatments received higher vigor scores and had greater top weights than plants in the control treatment. There were no significant differences in vigor scores, percentage living plants, or top and root weights of plants from the bark or peat soil amendment treatments and those from the control treatment.