Mike Roberts

Top Tips to Keep New Plantings Safe From Phytophthora

Many Florida citrus growers are undertaking new plantings, and there are many considerations to be taken for phytophthora, according to UF/IFAS assistant professor of plant pathology Megan Dewdney, during an OJ break. She shared it’s estimated that phytophthora, Phytophthora palmivora and Phytophthora nicotianae, causes losses to citrus yields anywhere from 3 percent to 6 percent every year; that’s a loss that equates to $20 million annually. Phytophthora is especially concerning for new citrus plantings. Dewdney shared recommendations for Florida citrus growers concerning phytophthora in new plantings.

New Plantings and Phytophthora Recommendations

In the meeting, Dewdney maintained that new citrus tree plantings require citrus growers to give special attention to root establishment in the era of citrus greening. This is because citrus greening negatively affects root growth. It means that a citrus tree infected with citrus greening cannot uptake nutrients and water as easily, and that the efficacy of phytophthora management is also reduced. Additionally, the infection of citrus greening makes the cost effectiveness of management uncertain, according to Dewdney. 

Dewdney gave recommendations for preventing phytophthora in new citrus tree plantings. Those recommendations include:

  • Avoid rootstocks that are deemed to be highly susceptible to phytophthora if you’re in a grove with a history of the disease.
  • Make sure the plant graft union is 6 to 9 inches above the soil during planting.
  • Ensure that there is adequate drainage and proper irrigation. Trees need optimal irrigation that is neither too wet nor too dry.
  • Use a weed management program to ensure there are no weeds around the tree competing with the tree for water and nutrients.
  • Try to avoid wounding the trees’ roots, trunks, and branches as it leaves the tree open to infection by phytophthora pathogens and other pathogens.
  • Take off trunk wraps early in the springtime and add in a fire ant treatment. Fire ants will get under the wraps to feed on bark, causing a great deal of damage.

In terms of treatment, Dewdney advised Florida citrus growers who suspect phytophthora to test their groves for the pathogen rather than just assume it is present to a dangerous degree. It is advised that sampling for the inoculum of either Phytophthora palmivora or Phytophthora nicotianae that results in 10 to 20 propagules/cmsoil or higher should be treated. Dewdney shared that treating for phytophthora during the fall and spring root flushes is a good course of action. Lastly, a good resource for phytophthora management is the UF/IFAS 2022–2023 Florida Citrus Production Guide.

BIO: Mike Roberts is the Vice President of the Frostproof, Fla.-based Griffin Fertilizer Co. Roberts joined the company in November 2011. He has spent the majority of his career in the fertilizer/agchem industry. Roberts earned a Bachelor of Science degree in citrus production from Florida Southern College in Lakeland. For more information, visit griffinfertilizer.com.

This column is sponsored by Griffin Fertilizer Co., and the opinions expressed herein may not reflect those of CFAN or of its advertisers.

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