The Toxicity of Five Native Thai Plants to Aquatic Organisms

Abstract

Five species or native Thai plants were bioassayed as toxicants against the cladoceran Moina sp., the fishes Oreochromis niloticus and Anabas testudineus, the shrimp Penaeus merguiensis, and the snail Cerithidea cingulata. The 24-h LC50 of each plant to each test species was determined. Diospyros diepenhorstii is the least effective plant extract against all five test organisms, while Maesa ramentacea and Sapindus emarginatus are the most effective plant extracts against Moina sp., 0. niloticus and A. testudineus. The lethal concentrations of all plant extracts to test fish are greater than that to shrimp. Moreover, all plant extracts are more effective against 0. niloticus than A. testudineus. Pittosporum ferrugineum and S. emarginatus have potential against snail pests. Among the five plants, M. ramentacea showed the highest toxicity to 0. niloticus. Toxicity to 0. niloticus or M. ramentacea (15-30 mg,J-1) was about half that of tea seed cake (6-15 mg,J·1). However, improvement of M. ramentacea toxicity is feasible. These results are useful for developing botanical pesticides for selective killing of undesired aquatic organisms.