The toxic effects of triorganotin(IV) compounds on the culicine mosquito, Aedes aegypti (L).

The structure-activity relationships of 25 triorganotin(IV) compounds were studied using the 4th instar A. aegypti larvae of the susceptible Liverpool Red-eye strain. The LC50 values of these compounds were compared with those of Malathion, DDT and Temephos. Maximal activities were obtained with tritolyltin chloride and its complexes with triphenyl-phosphine oxide and pyridine N-oxide, dimethyloctyltin- and diethyloctyltin acetates and tributyltin sucrose phthalate. A limited number of the triorganotin compounds was also tested with observed high activity against the 4th instar larvae of a local DDT-tolerant strain and against the 2nd instar larvae and adults of the susceptible strain. Delayed effect studies with both 2nd and 4th instar larvae showed high post-treatment mortality for the latter and, among the range of active compounds, the methyl- and aryltin compounds, in particular, were also found to exhibit high residual activities (100% kill) in laboratory tests conducted up to 10 weeks.

Toxicological studies of insecticides on Cullex quinquefasciatus Say and Aedes aegypti (L.).

Toxicity tests carried out on the larvae of A. aegypti and C. quinquefasciatus showed the former to be more tolerant of all insecticides tested, the order of toxicity being temephos greater than DDT greater than DDVP greater than malathion greater than lindane greater than carbaryl; also the second instar larvae of A. aegypti were more susceptible than fourth instar larvae. Enzyme kinetic studies on the total non-specific esterases and CarEs of adults and larvae of both species showed the Km values for total esterases of adult A. aegypti to be 0.333 mM vs 0.233 mM for C. quinquefasciatus; for adult CarEs it was 0.250 mM vs 0.220 mM. For total larval esterases of A. aegypti it was 0.112 mM vs 0.175 mM for C. quinquefasciatus: and for larval CarES it was 0.159 mM vs 0.213 mM respectively. Although some correlation between in vivo toxicity (LD50 values) and in vitro esterase inhibition (I50 values) between species could be discerned, overall correlation could not be established.

Toxicological studies of four insecticides against Musca domestica L.

Toxicological studies of four insecticides (malathion, carbaryl, bioresmethrin, and GH 74) against Musca domestica vicinia (Ampang strain) were undertaken with particular reference to age, sex and posttreatment temperature. It was found that bioresmethrin and GH 74, both with a negative temperature coefficient, have great potential for use against houseflies. In vitro inhibitory studies of head and body esterases showed that unlike malathion and carbaryl, bioresmethrin had only negligible effect on these enzymes. The possibilities of using bioresmethrin and GH 74 for controlling the housefly problem in the Cameron Highlands, West Malaysia are discussed.