“What should I do to help prevent Pythium and Phytophthora in my pepper and tomato crops early in the season?” is a question most often asked this time of year. In the past, the answer was simple. Apply mefenoxam (Ridomil Gold SL, Ultra Flourish, 4) or metalaxyl (MetaStar, 4). Problem solved, right?
Not exactly, with resistance development in Phytophthora (P. capsici) to both mefenoxam and metalaxyl, the correct answer isn’t as simple anymore. It’s important to remember that both chemistries will work very well as long as resistance hasn’t been detected on your farm. How do you know if you have resistance? The easiest way is to follow efficacy.
If the chemistries no longer provide the control they once did, then there is a good chance you have mefenoxam-insensitive Phytophthora populations present on your farm. Remember, once resistance develops it can linger around for a very long time. On the flip side, if you haven’t used either of these chemistries in the past 4 or 5 years, the P. capsici population may have reverted back to being sensitive to mefenoxam or metalaxyl and these chemistries might be highly effective once again. Importantly, proper crop rotation and resistance management is critical before resistance has had the chance to develop. Current options for pre-transplant applications include a Ranman (cyazofamid, 21) drench up to one week before transplanting or as a seedling tray drench at transplanting for Pythium and Phytophthora in tomato, pepper, and eggplant. Previcur Flex (propamocarb HCL, 28) has a label for the suppression of Pythium and Phytopthora in tomatoes and peppers. Phosphite fungicides such as ProPhyt, Rampart, and K-Phite (FRAC code 33) can also be applied as a pre-transplant drench in the greenhouse. Additionally, there are a number of biologicals such as Trichoderma, Streptomyces, and Bacillus products which can also be used in the greenhouse as drenches or incorporated in to the soilless mix to help suppress soil-borne pathogens. Remember, biologicals need to be applied without conventional fungicides and on a regular basis. At transplanting applications now include Ranman (cyazofamid, 21) in the transplant water or through drip irrigation for Pythium control. There is a section 2ee for the use of Previcur Flex (propamocarb HCL, 28) + Admire Pro (imidacloprid) in transplanting water for Pythium and insect control. Presidio (fluopicolide, 43) has a label for drip application for Phytophthora control when conditions are favorable for disease development. Additionally, phosphite fungicides, Pro-Phyt, Rampart, and K-Phite (FRAC code 33) can also be applied through drip irrigation at transplanting to help suppress Phytophthora blight. Unlike in past, there are a number of good options for early-season control of these diseases. It just takes a bit more planning ahead of time. For further details on use and crop labeled please refer to the specific fungicide label. Remember the label is the law.