Redhumped caterpillars are pests of ornamental and fruit trees.
Redhumped caterpillars (Schizura concinna) most often attack sweet gum (liquid amber), plum, and walnut trees, but they can also be found on pear, apricot, cherry, almond, apple, birch, prune, and willow.
Redhumped caterpillar lifecycle & identification
Redhumped caterpillars are 1 to 1-1/2 inches long and yellowish, with an orange or brick red head. The fourth segment is also red, with a distinct hump and two black spines (tubercles). Other segments have their own tubercles, but they are less visible. You may be able to see longitudinal stripes of white, brown, brick, or black along the body. In autumn, these caterpillars fall to the ground and spin themselves into a cocoon. The pupa is often found when working the soil. It is 1/2 inch long and reddish brown. In April and May, the moths emerge. Adult moths have a wingspan of 1 to 1-3/8 inches. The forewings are gray to reddish brown and the hind wings are pale white, grey or brown. A dark line may be visible along the back of the forewings. After mating, female moths lay clusters of 25 to 100 spherical, white eggs on the underside of young leaves. There can be 4 or 5 generations each year.
Redhumped caterpillar damage
Like most caterpillars, they are voracious feeders. Feeding in groups, they can quickly skeletonize leaves, making trees susceptible to sunburn damage. Heavy infestations can completely defoliate a tree, but the trees will normally recover, assuming they are otherwise healthy.
[Did you know that caterpillars rest with their rear ends up in the air?]
Redhumped caterpillar control
These pests have many natural predators, including spiders, damsel bugs, lacewings, and several parasitic wasps, so avoid using broad spectrum pesticides. If natural predators are not able to do the job, you can cut off twigs that contain caterpillars and either burn them or squash the bugs. If insecticides must be used, Bt (Bacillus thuringiensis) is effective against redhumped caterpillars. Just be sure to read the directions and follow them exactly. Timing is critical.
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