A presentation during a virtual seminar by a UF/IFAS citrus pathologist maintained citrus greening has a negative impact on phytophthora management.

Phytophthora is a pathogen that has been in Florida citrus groves for a long time; a Citrus Industry article maintains the pathogen was responsible for a three- to six-percent reduction in yield every year prior to the arrival of citrus greening, also known as HLB. However, since the arrival of citrus greening in Florida groves in 2005, citrus greening has made phytophthora management less effective. The article shared information offered by citrus pathologist Ozgur Batuman during a virtual seminar in February 2022 about how citrus greening affects the efficacy of managing phytophthora. See the details below.

Phytophthora Management and Citrus Greening

Citrus greening affects a citrus tree’s roots, among other things, leaving them susceptible to the pathogens that cause phytophthora in Florida citrus, Phytophthora nicotianae and Phytophthora palmivora.

Information pertaining to phytophthora management in Batuman’s presentation included:

  • “Improved fungicide timing, number of applications and rates are needed to achieve better control.”
  • “Wet conditions favor root infection cycles.”
  • “The susceptibility of roots to phytophthora is highest during very wet to very dry cycles.”
  • “Foot rot can be controlled with proper rootstock selection and by avoiding wounding and soil exposure of the scion. The graft union should be more than 6 inches above the soil.”
  • “Control root rot with good drainage and irrigation, use of clean nursery material, and by monitoring disease pressure.”
  • “Brown rot control includes eliminating fruit under the tree to reduce inoculum, raising tree skirts to increase air movement and promote drying of foliage, and application of preventive sprays of phosphite or copper. Time phosphite sprays in July. Spray in October if the fall rainy season is prolonged.”

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