How to Manage Pests

Pests in Gardens and Landscapes

Mineral deficiencies and toxicities

Evidence of lack or excess of certain minerals usually appears first in leaves but eventually affects fruit size, quality, or yield. Leaves may be pale to white or yellow, having chlorotic blotches along the veins or midribs. Leaves may also be mottled.

Solutions

Maintain a good fertilization and irrigation program. Make sure you apply the appropriate fertilizer at the right time. For oranges and grapefruit, apply nitrogen to the soil or foliage in late winter or early spring; lemons may receive nitrogen at any time of the year. Foliar applications of potassium and especially magnesium are most effective when the spring growth flush is two-thirds to three-fourths expanded. A leaf analysis may reveal toxic levels of certain minerals such as sodium, boron, or sulfur. An excess of these may be present in the soil naturally. Provide good soil drainage, and allow for extra irrigation to wash the salts below the root zone. Deficiencies can be corrected with chelated foliar sprays.

Mottling of leaf due to manganese deficiency
Mottling of leaf due to manganese deficiency

Yellowing
Yellowing due to magnesium deficiency
Chlorotic areas of zinc deficiency
Chlorotic areas of zinc deficiency

 


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