Florida citrus growers should start phytophthora management efforts soon to combat the pathogen and protect citrus trees.
“The spring 2026 root flush will be very important to sustain for long-term tree health and future flush, flowering, and fruit,” advised a UF/IFAS Tips of the Week article. It explained that Florida citrus trees had a tough winter with the very dry weather and the late January freeze, and that the trees “will be flushing as much as they can to replace the damaged canopy lost over the winter.” The spring root flush will quickly follow the leaf flush, and this means phytophthora pathogen will be active as well. The article advised Florida citrus growers to begin phytophthora management efforts soon. See the tips the article shared below.
Phytophthora Management Tips
The article shared these following tips for Florida citrus growers starting their phytophthora management programs:
- “Sample roots if there have been phytophthora problems historically or if there is a suspicion thereof.”
- “Refer to the phytophthora root rot chapter in the Florida Citrus Production Guide” for information on “how to sample for the most accurate propagule estimate,” and “stay away from the worst trees.”
- “Regardless of what product you choose for the first treatment of the year, mode of action rotation is essential. The Fungicide Resistance Action Committee (FRAC) codes help guide choices so that you do not need to be an expert in this area. If products have the same FRAC code, they are the same mode of action.”
- “The choices for phytophthora root rot management include mefenoxam (FRAC 4), fluopicolide (FRAC 43), phosphite salts (FRAC P 07) or oxathiapiprolin (FRAC 49). The order of use will depend on what your last treatment the previous season was and if you are concerned about brown rot.”
- Pay attention to “how many applications are allowed per season as several products are limited to one application.”
- “Phosphite salts during the summer do triple duty for phytophthora root rot, brown rot and algal spot if used in June or July.”
- “For root rot applications, it is best to start right after the spring flush. These are followed with late-spring and mid-summer applications to protect the summer root flushes. The final application is in the autumn to protect the roots that are the carbohydrate reserve for the winter.”
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