Citrus Leafminer

Unsightly leaves at the tips of new citrus branches are often caused by citrus leafminers. They originate from a tiny moth that lays eggs only on new citrus tree growth. Its larva then tunnels around inside the leaf, eating between the top and bottom surfaces of the leaf. This insect's activities cause the leaf to curl as well. While it makes a mess of new growth on citrus, it does not do significant damage to larger trees, and even very young citrus trees are unlikely to be permanently damaged. The UC Citrus Leafminer Pest Note has more detail about the life cycle and how to manage it. Along with other details, the Pest Note says:

"On mature backyard citrus trees, citrus leafminer rarely causes serious damage and management is normally limited to practices that limit succulent growth and protect natural enemies. Very young trees are more vulnerable to injury and insecticide treatment may occasionally be justified. However, available insecticides for backyard trees are not very effective and many products leave residues that kill natural enemies, compounding problems."