As we wrap up 2024, there is one more report that will be of some value as you think through disease management activities for 2025. As most of you are aware, the active ingredient in Ridomil, mefenoxam, is utilized to control Phytophthora crown and root rot of strawberry. Based on field observations, we have had concerns for some time that the Phytophthora pathogen is gaining resistance to mefenoxam. Though we only had four samples submitted for a limited survey (Berrien, Meriwether, Floyd, and Rabun Counties), none of the Phytophthora isolated from diseased plants were resistant to mefenoxam. That is good news, but it does not imply that resistance is not occurring somewhere in Georgia. If you suspect a control failure, work with your county agent to review the Phytophthora from your planting. Resistance may be observed due to carryover inoculum in a field or from transplants.

Though mefenoxam resistance was not observed in any isolated Phytophthora specimen, the Molecular Diagnostic Clinic in Tifton did observe resistance in Phytopythium isolates from Bulloch County. This is the first report of Phytopythium in Georgia, but this pathogen is also known to cause root rot in strawberry. It was also confirmed in South Carolina as well, so we need to be on the lookout for this pathogen in the future. Again, if you are having issues with root and crown rots in 2025, contact your local county agent for assistance.

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