MOLLUSCICIDAL ACTIVITY OF TOBACCO DUST AGAINST BRACKISHWATER POND SNAILS (CERITHIDEA-CINGULATA GMELIN)

Toxicity tests on the effect of tobacco dust against brackishwater pon d snails (Cerithidea cingulata Gmelin) of various stages or size range s were conducted under controlled laboratory conditions. The 72-h LC50 for the juveniles, sub-adult and adult snails are 30, 87 and 166 kg h a(-1), respectively, while the 72-h LC99 are 290, 522 and 712 kg ha(-1 ), respectively. The nicotine content of the tobacco dust used was 2.8 %. Lethal concentration increased as the life stages or size of the sn ail increased. Molluscicidal activity also progressively increased wit h time of exposure. The nicotine content and toxicity of different typ es of tobacco [flue-cured (neutral), flue-cured (full-flavor), burley and batek (full-flavor)] were determined on adult snails. Lethal conce ntrations (LC50) and (LC99) decreased as nicotine content of the tobac co dust increased indicating a higher molluscicidal activity. The effe ctive application rate is affected by the nicotine content of the toba cco dust. An equivalent nicotine concentration of ca 24 kg ha(-1) corr esponded with the 72-h LC99 under laboratory conditions. Seven-day bio assay experiments on the effect of tobacco dust on two size groups of milkfish juveniles (0.5 and 2-3 g) showed no mortalities up to the con centration lethal to the pond snails. (C) 1998 Elsevier Science Ltd. A ll rights reserved.