What do longhorn beetles eat? The feeding habits of larvae and adults differ greatly.

Longhorn beetles are the collective name for insects of the family Cerambycidae in the order Coleoptera. They are extremely diverse, and the vast majority feed on plants. Their life cycle goes through four stages: egg, larva, pupa, and adult. The food sources of the larval and adult stages differ markedly, and the larval stage is the period of heaviest feeding and damage.

Longhorn beetle larvae mostly hide inside trunks, branches, or roots, mainly gnawing on the xylem and phloem and boring curved tunnels through the tree body. Because the larvae feed deep within the wood, often only the expelled wood dust and frass can be seen on the outside. By the time they are discovered, part of the tree body has often already been hollowed out, the tree's vigor declines accordingly, and branches are prone to drying up and breaking.

The feeding habits of adults differ from those of larvae. Most species are active during the day, gnawing on the epidermis of tender branches, leaves, bark, or flowers and fruits to supplement nutrition, while some adults feed very little and mainly mate and lay eggs after emergence. When laying eggs, adults usually bite through the bark and deposit eggs under the bark or in crevices, and the newly hatched larvae immediately bore into the tree to continue feeding.

Longhorn beetles have a very broad host range. Mulberry, poplar, willow, elm, pagoda tree, as well as many fruit and forest trees such as apple, peach, fig, and citrus, are all subject to damage. Common species include the mulberry longhorn beetle, the citrus longhorn beetle, the peach red-necked longhorn beetle, and the pine sawyer beetle, and different species each have preferred tree species.

Because the larvae hide inside the trunk to feed, longhorn beetle control should target the adult stage and the period when larvae have just hatched. Methods can include hand-collecting adults, looking for egg-laying marks, hooking out or sealing bore holes, and whitewashing tree trunks. During routine inspections, if wood dust is found being expelled from branches or trunks, it should be dealt with promptly to avoid the tree body becoming hollowed out and difficult to recover.