Evaluation of seven green manure crops as antagonists against larvae of Scepticus griseus (Coleoptera: Curculionidae), an insect pest of vegetables and field crops

We compared the survival of larvae of Scepticus griseus (Roelofs) (Coleoptera: Curculionidae) fed on roots of carrot Daucus carota L. subsp. sativus (Hoffm.) Arcang. (Apiaceae), peanut Arachis hypogaea L. (Fabaceae), and seven species of green manure crops in a conical tube experiment to find crops that can be grown in the habitat of this weevil without increasing its numbers. Many weevils survived or emerged when raised on carrot, peanut, African marigold Tagetes erecta L. (Asteraceae), and rye Secale cereale L. (Poaceae), some on mustard Brassica juncea (L.) Czern. (Brassicaceae) and Avena strigosa Schreb. (Poaceae), few on showy crotalaria Crotalaria spectabilis Roth (Fabaceae) and Sudan grass Sorghum × drummondii (Nees ex Steud.) Millsp. et Chase (Poaceae), and none on sorghum Sorghum bicolor (L.) Moench (Poaceae). Thus, showy crotalaria, sorghum, and Sudan grass are not suitable and mustard and A. strigosa are less suitable as hosts for S. griseus , and therefore could be grown as green manure crops in areas where the weevils are found. However, investigation of the effects of the plants on oviposition by weevils is needed to prevent immigration of adults to new habitats.