Symptoms include the yellowing of leaves with an inverted v of green tissue at the base of the leaf. Manganese deficiency occurs in all citrus growing areas of New Zealand. Symptoms include the development of an interveinal yellowing with a band of darker green along the midrib and veins. Zinc deficiency produces symptoms which are similar to Mn deficiency but the interveinal yellowing is less blotchy and more clearly defined. In extreme cases leaves can be small, narrow, pointed and rosetted in the classical little leaf symptom.
Zinc deficiency can also affect fruit shape.
Manganese and Zn deficiency often occur together and can be corrected together or singly. The most effective means of correcting both disorders is by foliar sprays. The urea is helpful for increasing the uptake of Mn and Zn. Foliar sprays should be applied on their own without the addition of insecticides or fungicides. They should be applied at a time when there is plenty of young foliage, as older leaves are less efficient at absorbing nutrients.