How to Manage Pests

Pests in Gardens and Landscapes

Fertilizing

Citrus occasionally suffers from micronutrient deficiencies such as zinc or iron. These deficiencies can be corrected by applying a foliar application of a liquid chelated micronutrient solution as the new growth emerges in the spring. You can also apply micronutrients in the sulfated form, such as zinc sulfate or iron sulfate, to the soil.

Most mature citrus require regular fertilization with nitrogen. Typically, most other nutrients are available in sufficient amounts in the soil. Nitrogen should be applied in January or February just prior to bloom. The second application then can be applied in May and perhaps a third in June. Avoid late-season fertilization as it may affect fruit quality, delay fruit coloring, and make the rind rough. Dwarf plants or trees in containers with restricted root space may require less fertilizer.

Maintaining a good fertilizing program can help preserve a tree's natural resistance to fungal diseases such as oak root fungus. Be careful not to overfertilize as this will cause excessive new growth, which makes trees susceptible to other disorders such as bacterial blast.

Suggested application rates of nitrogen

(Divide into 2 or 3 applications)

  • 1st year: 1 tablespoon nitrogen fertilizer 3 times per year, per tree.
  • 2nd year: 0.25 lb actual nitrogen per tree
  • 3rd year: 0.5lb actual nitrogen per tree
  • 4th year: 0.75lb actual nitrogen per tree
  • 5th year:1 lb actual nitrogen each year
Zinc deficiency
Zinc deficiency

1 pound of actual nitrogen equals about 5 lb of ammonium sulfate per year, or 100 lb of composted cow manure each year. Organic fertilizers such as manure, bloodmeal, etc. could be applied in the fall under the tree canopy.


Statewide IPM Program, Agriculture and Natural Resources, University of California
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