ARS | Publication request: Managing Phytophthora Disease with Fungicides

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2008
Publication Date: July 26, 2008
Citation: Hausbeck, M.K., Keinath, A.P., Kousik, C.S., Matheron, M.E. 2008. Managing Phytophthora Disease with Fungicides. Phytopathology. APS Centennial celebration in Minneapolis, MN, July 26, 2008.

Technical Abstract: Phytophthora capsici ranks as a top threat to production of Cucurbitaceae, Solanaceae and most recently Fabaceae vegetables. Available and effective fungicides for disease management are limited and populations of P. capsici in many growing areas have become insensitive to mefenoxam. Efficacy of fungicidal and suppressive products was researched through monitoring sensitivities, identifying effective active ingredients and optimizing application and timing. Isolates insensitive to cyazofamid were recently identified in southeastern US. SC isolates were very sensitive to dimethomorph, sensitive to zoxamide and moderately sensitive to cymoxanil in 3 in vitro assays for mycelial growth and zoospore production and germination. Baseline isolates collected before commercial use of these fungicides were sensitive to all 3 fungicides. In similar mycelial growth assays, isolates from southeastern US (NC, SC, GA, FL) were very sensitive to fluopicolide and mandipropamid. In AZ, pepper plant survival was significantly higher when soil was treated with fenamidone + propamocarb, cyazofamid, fluazinam, fluopicolide, dimethomorph, and mandipropamid in all trials. In MI, fungicides applied using current technology to enhance coverage when cucumber fruits were 2.5, 7.6 and 12.7 cm in length significantly reduced fruit rot. A comprehensive management strategy for P. capsici integrates cultural practices and timely application of effective fungicides.