Larva

Pests

The immature, often worm-like feeding stage of an insect that undergoes complete metamorphosis, typically the stage that causes the most damage to trees.

A larva is the juvenile form of an insect that undergoes complete metamorphosis, progressing through egg, larva, pupa, and adult stages. In tree care, the larval stage is usually the most damaging because it is the primary feeding stage. Caterpillars (moth and butterfly larvae), grubs (beetle larvae), and maggots (fly larvae) all represent different types of larvae affecting trees.

The damage caused by larvae varies with the species and feeding habit. Defoliating larvae like tent caterpillars and spongy moth caterpillars consume leaves. Wood-boring larvae like those of longhorned beetles and clearwing moths tunnel through cambium, sapwood, or heartwood. Leaf-mining larvae feed within the leaf tissue itself, creating characteristic serpentine trails or blotch mines.

Identifying the specific larval pest is essential for effective management. Key identification features include body shape, color, number of prolegs (fleshy false legs), presence of hairs or spines, and feeding location. Many larvae can be managed effectively with targeted biological insecticides like Bacillus thuringiensis (Bt), which specifically affects caterpillars without harming beneficial insects. Timing applications to coincide with early larval stages maximizes effectiveness.