SUITABILITY OF THE NORTH-AMERICAN WEEDS SESBANIA-EXALTATA AND S-DRUMMONDII (LEGUMINOSAE) AS HOSTS FOR NEODIPLOGRAMMUS-QUADRIVITTATUS AND TRICHAPION-LATIVENTRE (COLEOPTERA, CURCULIONIDAE) IN ARGENTINA

Neodiplogrammus quadrivittatus (Oliver) and Trichapion lativentre (beg uin-Billecocq) are 2 South American weevils successfully used for the biological control of Sesbania punicea (Cavanille) Benth. in South Afr ica. The potential of these insects as control agents for the weeds Se sbania exaltata (Raf.) Rydb. and S. drummondii (Rydb.) Cory in the Uni ted States was studied in Argentina. Estimation of adult consumption, the food preference of adult insects on 5 species of Sesbania (3 nativ e hosts and the 2 weeds mentioned above), the capacity of the insects to complete their life cycle on the weeds, and the weed infestation by wild populations in the laboratory garden were studied. The consumpti on of N. quadrivittatus on both north American weeds did not differ fr om that on native hosts. Similar consumption was observed for T. lativ entre feeding on S. drummondii. S. exaltata showed the lowest consumpt ion. The feeding preference of N. quadrivittatus was similar to that o f its natural host plants. In the case of T. lativentre, results on on ly S. drummondii were comparable to that of its natural hosts. Both in sects were able to complete their life cycles on the weeds. In the gar den, there was a marked preference by the weevils for S. drummondii. S . exaltata was not attacked by T. lativentre and no test was carried o ut with N. quadrivittatus. We concluded that both insects are good bio control candidates for S. drummondii, whereas only N. quadrivittatus i s a promising control agent for S. exaltata.