Red-humped caterpillars develop into a type of prominent moth (Family: Notodontidae) and are sometimes defoliators of ornamental trees and shrubs in their larval stage. Host plants of S. concinna include apple and crabapple, but many woody plant hosts have been reported, comprising of but not limited to: pear, cherry, plum, sweetgum, walnut, redbud, and willow. The caterpillars of this species are commonly encountered and widespread throughout North America. The adult moth is grayish brown, has a wingspan of approximately 1 inch, and is rarely seen or captured. One generation is produced per year in northern locations, with a partial second generation possible in the Northeast, although multiple generations per year (up to 5) have been reported in warmer areas of the red-humped caterpillar range. Eggs are white and spherical in shape and can be laid in groups of 25-100 on the undersides of leaves. Young caterpillars will feed in groups, but disperse and feed separately as they grow and mature in size. The mature caterpillars of the species are spectacular in their color and ornamentation. They have red or black head capsules, are yellow in color with white longitudinal stripes bordered in red down the sides of the body, and possess black projections (tubercles) on each body segment. The fourth body segment counting from the head capsule (not counting the head but just behind it) has a red, pronounced hump with prominent black tubercles that are larger (and longer) than the others present on the body. At rest, these caterpillars may have their rear-end elevated. Caterpillars mature by August or September and drop to the ground. The prepupal larva overwinters (Wagner, 2005). Pupae are shiny and reddish-brown in color and may be enclosed within a silken cocoon and are found in the soil or leaf litter nearby susceptible host plants. Adult moths are comparatively drab and dull when considered next to the caterpillars of this species; moths are light gray to brown in color with some white markings. Some other species of native caterpillars in this same genus (Schizura) may also be active on similar hosts in the eastern United States. Not mentioned in this Guide, species include but are not limited to: the unicorn caterpillar (S. unicornis), the checkered-fringe prominent (S. ipomoeae), and the chestnut schizura (S. badia) (Johnson and Lyon, 1991; Wagner, 2005).
Caterpillars will feed in groups when first hatched from their egg, often skeletonizing the underside of leaves initially. As the caterpillars grow in size, they are capable of consuming entire leaves. They often feed on the same limb/branch together in a group, stripping everything except leaf veins. These larvae are typically more problematic on smaller trees, whereas larger trees may not be extensively impacted. However, periodically, outbreak populations of this species may occur over a widespread geographic area and defoliation of entire trees may occur. Problematic populations of the red-humped caterpillar on fruit trees can result in sparse foliage and thus sunburned fruit (Johnson and Lyon, 1991).
The adult moths of this species rarely come to lights or light traps and are rarely seen or captured. Visually monitor for the caterpillars of this species on susceptible host plants from May to November (Wagner, 2005).
If caterpillars are found in aggregations or groups feeding on an ornamental host plant, they can be removed with a gloved hand and destroyed or dropped into a can of soapy water. This will reduce the population on a single host plant, and may help prevent further defoliation of an ornamental planting. Note that caterpillars will collectively participate in warning displays. When disturbed, caterpillars will lift their hind end in the air. If further harassed, caterpillars will thrash violently from side to side and even regurgitate a drop of liquid.
Many parasitic wasps and tachinid fly species have been reported as natural enemies of this caterpillar. Predatory insects have also been reported. Species include, but are not limited to: Cotesia schizurae, Hyposoter fugitivus, Trichogramma spp., and others. Typically, these natural enemies can keep the red-humped caterpillar population below outbreak levels.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Azadirachtin (NL)
Bacillus thuringiensis subsp. kurstaki (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Bifenthrin+imidacloprid (L)
Chlorantraniliprole (NL)
Chlorpyrifos (larvae) (N)
Chromobacterium subtsugae (NL)
Cyantraniliprole (NL)
Cyfluthrin (NL)
Flonicamid+cyclaniliprole (N)
Tau-fluvalinate (NL)
Gamma-cyhalothrin (L)
Horticultural oil (L)
Indoxacarb (L)
Insecticidal soap (NL)
Isaria (paecilomyces) fumosoroseus (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Neem oil (NL)
Pyrethrin+sulfur (NL)
Spinetoram+sulfoxaflor (N)
Spinosad (NL)
Tebufenozide (NL)
Select reduced risk active ingredient options, if considering chemical management of this insect, to preserve natural enemies. Typically, management of this native species is not necessary.
Active ingredients that may be applied systemically include: acephate (injection), abamectin (injection), acetamiprid (injection), azadirachtin (injection, soil drench), chlorantraniliprole (soil drench), cyantraniliprole (soil drench, soil injection), and neem oil (soil drench).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
