See recommendations from a UF/IFAS plant pathologist on treating algal spot in Florida citrus groves.

Algal spot has not been a big problem in Florida citrus groves since the 1960s and 1970s, but it has been become an issue in the last five years or so. The issue prompted UF/IFAS plant pathologist Megan Dewdney to research the disease and run some trials to come up with recommendations for treating the disease. She presented her results during a virtual Florida Citrus Growers’ Institute presentation, according to a Citrus Industry article. See the details below.

Algal Spot Recommendations

Dewdney maintained that algal spot is most likely to continue to be seen in Florida citrus groves in the future as average temperatures increase due to climate change. Hard to spot at first, it presents as bark thickening around lesions that can lead to further cracking and loss of bark in small pieces, according to a 2012 Citrus Research and Education Center publication. Dewdney shared that wind is the “main means of spread,” but that rain and moving water, insects, and agitation of the tree canopy could spread the disease as well.

The historical recommendation for treating the disease was copper, but citrus growers shared with Dewdney that it wasn’t working. She ran trials on phosphite, copper, and oxathiapiprolin after hearing that blackberry growers were having success with phosphite. Her recommendations include:

  • The best disease reduction was from phosphite; it did not respond to copper.
  • The disease is associated with tree stress, so Dewdney recommended using cultural practices to reduce plant stress.
  • Using optimal nutrition and irrigation to reduce plant stress
  • Utilizing the thinning of canopies for increased air movement, though Dewdney said “Unfortunately, we already have quite thin canopies and plenty of air movement.”
  • Keeping other diseases and pests managed to reduce plant stress.

Griffin Fertilizer is committed to helping both growers and ranchers make sound agronomic and economic decisions in order to maximize the health of their grove and pasture. As a full-service custom dry & liquid fertilizer blender and crop protection product distributor, we will continue our mission to further advance Florida agriculture. For questions or concerns about your farm or pasture, contact us and one of our team will be in touch.