Zinc deficiency, sometimes called little-leaf disease, commonly occurs in fruit and nut trees. Zinc deficiency is rare in palms.
Zinc is usually present in soils in adequate amounts, except where development or grading removed topsoil. More commonly, plants cannot adequately absorb the zinc that is present because of an adverse soil environment or inappropriate cultural practices. Example causes of zinc deficiency include soil that is abnormally high in organic matter or sand or high in pH. Unhealthy roots (e.g., from crushing or other physical injury, soil-dwelling nematodes, or root decay pathogens) and poor irrigation practices (e.g., overwatering and waterlogging) can also cause plants to develop zinc deficiency symptoms.
In broadleaves mildly deficient in zinc, leaves are uniformly yellowish or pale between the veins and may develop dead spots. Symptoms are usually most apparent on new foliage in the spring. Severely deficient plants bloom and leaf out late, sometimes several weeks later than normal. When buds open, leaves are atypically pointed, narrow, undersized, and yellowish. Internodes are often shortened, resulting in tufts of leaves (rosettes, or witches’ brooms). Older leaves may drop prematurely. Symptoms of zinc deficiency commonly resemble those of iron deficiency, manganese deficiency, or herbicide phytotoxicity from exposure to glyphosate or preemergence herbicides.
Zinc-deficient conifers have undersized, yellowish needles that may drop prematurely. When plants are severely affected, branches are undersized and may die back.
Diagnose zinc deficiency based on characteristic foliar symptoms and assessment of conditions that affect zinc availability as described above. Laboratory analysis of soil can reveal high pH, excessive organic matter or sand, or high phosphorus concentration, which reduce zinc availability.
Remedy zinc deficiency by improving cultural practices and soil conditions to assist zinc uptake by roots as described in iron deficiency under "Solutions." If appropriate, zinc chelate can be applied according to the product instructions. Be aware that foliar application of zinc chelate can be phytotoxic and the proper timing of application is important. See "Soil and Fertilizer Management" in the California Master Gardener Handbook for more information.
Adapted from the publication above, Abiotic Disorders of Landscape Plants, UC Agriculture and Natural Resources, and Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).
Zinc deficiency in citrus leaves, severe to mild (left to right).
Small, yellowish almond leaves in tufts due to zinc deficiency.
Lateral buds developing slower than terminal buds and narrow, stiff leaves indicate zinc deficiency.
Citrus leaves deficient in manganese (top row), zinc (bottom row) and both elements (middle row).