Zinc deficiency

Reduction in leaf size and leaf yellowing on Zn-deficient crop (J. O'Sullivan).

Loss of green pigment between leaf veins on a mature leaf (J. O'Sullivan).

- reduced size and narrow shape of young leaves.

- lateral lobes may be especially reduced, and point more acutely towards leaf tip.

- young leaves may be pale

older leaves may show interveinal chlorosis (a mottled pattern of paler areas in between the leaf veins).

May be caused by soil alkalinity (high pH) such as on coral or limestone soils, or after application of lime.

Cassava and citrus show symptoms more readily than sweetpotato - they are good indicators if they are grown nearby.

Confirm diagnosis by painting the surface of half a leaf with zinc sulfate solution, and symptoms should be reduced in a few days, compared with the other half.