ARS | Publication request: Evaluation of Fungicides for Control of Phytophthora Blight of Watermelon in North Carolina and South Carolina

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2008
Publication Date: July 26, 2008
Citation: Adams, M.L., Holmes, G.J., Kousik, C.S. 2008. Evaluation of Fungicides for Control of Phytophthora Blight of Watermelon in North Carolina and South Carolina. Phytopathology. 98:S10.

Technical Abstract: Phytophthora blight, caused by Phytophthora capsici, is an important disease of cucurbits in the eastern U.S. Fungicides, crop rotation, and water management are recommended to control the disease. Watermelon (Citrullus lanatus) poses a particularly difficult challenge to disease control because of the duration of fruit-soil contact. In each state, fungicides were used at labeled rates and applied at approx. 7-day intervals. Disease incidence was recorded (No. fruit rotted by P. capsici/ total number of fruit). Disease incidence in non-treated plots averaged 63% across 2 trials. In SC in 2006, Captan provided 68% disease control (calculated as % of non-treated) while mandipropamid (Revus) controlled disease at 66%. When Revus was combined with phosphonate (ProPhyt) and fixed copper (Kocide 2000) in SC, disease control was 74%. In 2007 in NC, captan, mandipropamid and folpet (Folpan) controlled disease at 69%, 66%, and 65%, respectively, but when captan was combined with Kocide, disease was controlled at 85%. In 2006 in SC, the same treatment of captan + Kocide provided only 45% disease control and in 2007 in NC, Revus + ProPhyt + Kocide controlled disease at only 48%. These results show that product performance varies by year and location and even the best treatment may not provide commercially acceptable levels of control in watermelon.