Explore all of the current knowledge on combating preharvest fruit drop that is related to citrus greening.

Preharvest fruit drop that is connected to citrus greening can claim up to 60 percent of a crop, depending upon “the disease severity, cultivar and environmental factors,” according to a Citrus Industry article authored by UF/IFAS CREC assistant professors. Unfortunately, researchers do not yet know why citrus greening causes fruit drop, but the article did share all of the current knowledge to date. See highlights below.

Preharvest Fruit Drop Related to Citrus Greening

The article summarizes that “HLB-associated fruit drop is related to tree canopy density and limited water availability to the fruit.”

Options for reducing preharvest fruit drop include:

  • “One strategy is to maintain a constant water supply through irrigation. Applying large volumes of water at once is not beneficial for HLB-affected trees as significant portions of water leach out of the root system before the tree can take up the water. Instead, trees should be provided with small amounts of frequent irrigation. The goal is to give trees enough water, so fruit growth and drop is not influenced.”
  • “A second strategy is to reduce transpiration. In HLB-free trees in Italy, reflective materials like kaolin and calcium carbonate improved water relations and photosynthesis. This resulted in at least 80 pounds per tree more fruit and reduction in preharvest fruit drop compared to untreated trees.”
  • “Plant growth regulators are a third strategy. Foliar applications of gibberellic acid (20 grams active ingredient per acre) on Valencia from September to January have shown promising results in HLB-affected sweet oranges.”

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