Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 2/14/2011
Publication Date: N/A
Technical Abstract: Fruit rot, caused by Phytophthora capsici is an emerging disease in most watermelon producing regions of Southeast US. The National Watermelon Association (NWA) has considered this disease as a top research priority because of losses incurred by the growers in NC, SC and GA. For the past several years we have been conducting trials to identify effective fungicides to manage fruit rot of watermelon. Based on three years of field testing (2006-2008) under severe disease pressure, we identified two relatively new fungicides Revus and Presidio that are labeled for use on cucurbits. In field trials conducted in 2010, the rotation of Presidio and Revus was the best treatment and significantly reduced fruit rot compared to non-treated check. Application of the systemic resistance activator (SAR), Actigard every week for five weeks also significantly reduced fruit rot. Forum, Zampro, Prophyt + Kocide, and Revus rotated with Prophyt + Kocide treatments also significantly reduced fruit rot compared to non-treated check in the field. Ridomil Gold, the standard treatment was not significantly different from the non-treated check as expected, because mefenoxam insensitive strains were present in the field. Symptomless fruit harvested four days after the last spray application were inoculated and maintained in a humid chamber that favored fruit rot development. The development of disease lesions and sporulation on fruit treated with fungicides Zampro, Forum, and rotation of Presidio with Revus in the humid chamber were significantly less compared to the non-treated check. Resistance in the pathogen population to fungicides such as Ridomil Gold and Ranman has been identified previously. Thus, there is always a possibility of P. capsici developing resistance to the above mentioned fungicides. Therefore these fungicides should be rotated or tank mixed with other available fungicides to prolong their usefulness in managing fruit rot.