Genista broom moth (Uresiphita reversalis), is a native North American moth that feeds primarily on plants in the pea family (Fabaceae), including Baptisia, lupine, false indigo bush, and other related plants.
Damage
The caterpillars are the damaging stage of the insect. Young larvae feed together and may produce webbing among the leaves. As they grow, they consume large amounts of foliage and can quickly strip leaves from a plant. Heavy infestations may leave Baptisia nearly defoliated. Despite their dramatic appearance and feeding habits, established plants usually recover and are rarely killed by the damage. However, repeated severe defoliation could stress young or recently established plants.
Mature caterpillars are about 1 inch long and are easily recognized by their tan to greenish-brown bodies, black spots, yellow markings, and scattered white hairs.
Life Cycle
Although genista broom moths can produce four or more generations annually in southern states, Iowa's shorter growing season likely limits them to one or two generations per year. Adult moths emerge in late spring and summer, mate, and lay clusters of eggs on host plants. The caterpillars hatch and begin feeding in groups, often within silken webbing. After completing several larval stages, they pupate in loose cocoons on or near the host plant. The species generally overwinters in the pupal stage and resumes development the following season.
Management
Management is often unnecessary because the damage is primarily aesthetic, and established Baptisia plants usually recover. When caterpillars are nearly full-grown, most feeding has already occurred, and insecticide applications provide limited benefit. At that stage, hand-picking caterpillars and dropping them into soapy water is often the most practical option. Branches can also be shaken to dislodge caterpillars.
If control is desired, the best time to act is when caterpillars are small. Products containing Bacillus thuringiensis (Bt) are effective against young caterpillars and have minimal impact on most beneficial insects. Spinosad and other labeled caterpillar insecticides may also provide control when larvae are still actively feeding.
Because the genista broom moth is a native species and infestations are often sporadic, many gardeners choose to tolerate the temporary defoliation and allow the plants to recover naturally. By the time large caterpillars are discovered in midsummer, the damage is typically already done, and control measures provide little additional benefit.
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