How Different Techniques Hold Up to Diseases

Josh McGill Citrus Expo, Diseases, IPCs

How well reflective mulch, kaolin clay and individual protective covers (IPCs) hold up to HLB, canker and greasy spot diseases was researcher Megan Dewdney’s topic at the 2022 Citrus & Specialty Crop Expo. Dewdney is a University of Florida Institute of Food and Agricultural Sciences associate professor of plant pathology at the Citrus Research and Education Center. 

Individual protective covers do not protect trees from greasy spot.

The research project Dewdney cited involved Valencia orange trees on Kuharske rootstock. Treatments were representative of current industry practices, including monthly insecticide treatments and microsprinkler irrigation.

The conclusions Dewdney presented include:

  • By the time HLB symptoms are apparent, 10% to 20% of trees are infected.
  • No trees under IPCs have had detections of Candidatus Liberibacter asiaticus, the causal bacterium of HLB.
  • Kaolin clay may not be a good tool for newly planted trees.
  • Canker will affect most young healthy trees if they are in an area with previously infected trees. Applications of Blockade were helpful with copper for canker management. IPCs slow wind speeds enough to reduce canker infection. Lower presence and severity of canker in IPCs means only some trees have canker and there are fewer lesions.
  • Reflective mulch allows trees to flush well. More flush means more canker-susceptible tissue.
  • Greasy spot is everywhere; most trees are infected the first year. Greasy spot tends not to get to damaging levels on Valencia. Oil could keep the disease in check.

Dewdney concluded with these take-home points:

  • Young trees can be kept HLB-free for more than 2.5 years with IPCs. Trees in all other treatments were 80% to 100% infected.
  • Citrus canker was greatly reduced in IPCs.
  • Greasy spot got worse over time in IPCs but was equivalent in other treatments.
  • IPCs can safeguard young trees from HLB better than reflective mulch or kaolin clay, but other diseases will need to be managed.

See Dewdney’s full Expo presentation here.

About the Author

Ernie Neff

Senior Correspondent at Large

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