NC State Extension Publications

Description and Biology

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Baptisia Seed Pod weevils, Apion Rostrum, are also called baptisia weevils, wild indigo weevils, or Say’s weevils. They are tiny, black beetles with mouthparts located at the tip of a long beak or snout. Including the snout, females are about 1/4 inch long and males about 1/8 inch. These weevils typically oviposit eggs singly into seed pods as the pods begin to swell, but multiple eggs can be laid. Female weevils may have the ability to decide how many eggs to lay in a pod to maximize offspring fitness. (Too many grubs in a pod may cause some to starve.) In addition, females may deter other females from laying additional eggs in a pod by depositing a pheromone deterrent. Adults eat leaves and flowers in very early summer, moving from one Baptisia species to the next as they bloom. When the green pods form, the females bore into them, preferring the larger pods. According to one source, after she excavates the hole in the pod and lays her egg, she uses her snout to push the egg into the pod. Baptisia Seed Pod weevils grubs are typical weevil grubs with white or yellowish, legless bodies and pale brown heads. They feed on developing seeds causing the plant to abort the pods. The grubs pupate inside the pods. New adults must either bore a tiny escape hole in its side or wait for the pod to dry and split to escape. Some adults overwinter in the pods or in soil.

Baptisia seed pod weevil

Baptisia seed pod weevils are small, dark, and handsome.

Baptisia seed pod weevil adults chew

Baptisia seed pod weevil adults chew their ways out of the infested pod or wait for the pod to split.

Baptisia seed pod weevil eggs

Baptisia seed pod weevil eggs are extremely small and only found inside pods.

Baptisia seed pod weevil grubs

Baptisia seed pod weevil grubs are typical weevil grubs.

Host Plants

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Baptisia seed pod weevils attack the pods of several wild indigos and false indigos. It seems that the denser flower stalks that make some species of Baptisia more attractive to bumblebees (an important pollinator) also make them more attractive to the weevil. Populations of baptisia seed pod weevils wax and wane, but when abundant they may destroy most of the summer’s seed crop.

Residential Recommendations

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In one study, "Tanglefoot" applied to the stems of wild indigo reduced the amount of seed predation by trapping the adult beetles crawling up the stems. Insecticides have also been shown to reduce damage when applied in the spring and early summer. Baptisia seed pod weevils feed on the foliage, flower buds, and blossoms. One of the pyrethroids labeled for landscape us applied before the flowers open or after flowering should help protect the plants and pods. This weevil will probably continue lay eggs during the summer so it is a good idea to spray the plants after blooming as well as before. A problem with spraying while the plants are in bloom is that you may kill pollinators, which is un-American.

Other Resources

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For assistance with a specific problem, contact your local Cooperative Extension center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology & Plant Pathology

Publication date: May 14, 2019
Revised: Oct. 9, 2019

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