Chronic toxicity of three insecticides (carbaryl,fenthion and lindane) in the freshwater snail Lymnaea stagnalis

A chronic intoxication with carbaryl, fenthion and lindane was induced in young snails. The parameter k of the von Bertalanffy's equation showed clearly the growth changes induced by these insecticides. In all cases the fecundity of intoxicated snails was reduced. Among these three insecticides, lindane was the most toxic, carbaryl the least.     

Relative toxicity of different combinations of temephos and fenthion with Solanum xanthocarpum extract against anopheline larvae

The relative toxicity of different concentrations of temephos and fenthion with petroleum ether root extract of Solanum xanthocarpum (Schrader) at 1 : 1, 1 : 2 and 1 : 4 ratios was evaluated against Anopheles stephensi (Liston) larvae. All combinations exhibited antagonism at concentrations lower than LC₅₀ values and synergism at concentrations higher than their LC₉₀ values. A 1 : 1 product ratio was the most effective.     

The effects of five organophosphorus insecticides on thermal stress in tadpoles of the Pacific tree frog, Hyla regilla

Three week old tadpoles of Hyla regilla were exposed to the insecticides temephos, fenthion, methyl parathion, chlorpyrifos, and malathion for 24 h at concentrations less than and at field applied rates as recommended for mosquito control in California. The thermal tolerance was significantly lowered by all chemicals and concentrations tested. Chlorpyrifos and methyl parathion were the most active compounds tested whereas malathion was the least toxic to H regilla tadpoles. Activity was depressed, in comparison to control tadpoles, by the chemicals methyl parathion (100 ppb) and malathion (500 ppb).     

Action de pesticides chez des insectes en fonction de leur etat physiologique: Etude de 2 insecticides et d'un melange d'herbicides chez les larves aquatiques de cloeon. (Ephemeropteres).

For the larvae of the ephemeron Cloeon, our studies of acute toxicity show that the degradation products of fenthion are more toxic than the insecticide itself.Doses of fenthion and lindane, responsible of a hight mortality, lead to a decrease in the moulting frequency of these larvae. A mixture of herbicides and degradation products of fenthion gave different results.

     

Effects of ''closed'' houses on the Aedes aegypti eradication programme in Trinidad

The effects of closed (i.e. locked) houses on the efficiency of control measures against Aedes aegypti (L.) were monitored weekly for 1 year (March 1981 to February 1982) using ovitraps in the towns of Felicity and Trincity, Trinidad. Regular anti-aegypti activities comprised source reduction, focal treatment with larvicidal 1% temephos sand granules and perifocal treatment with 40% wp fenthion. In Felicity, only 6% of houses were closed and after each treatment cycle ovitrap indices showed 100% control. In Trincity, 32% of houses were closed and after each treatment cycle reductions in ovitrap indices were less than 50%. Ae.aegypti eggs sampled in ovitraps totalled 493 (1-70 per positive paddle) in Felicity and 2310 (1-75 per positive paddle) in Trincity; twenty-three ovitraps were found to be positive in Felicity and 247 in Trincity. Ae.aegypti was successfully eliminated from Felicity during weeks 40-52 using focal/perifocal treatment monitored by ovitraps. Control failure in Trincity was attributed to the survival of untreated Ae.aegypti populations in closed houses. Recommendations to improve gaining access for inspection and treatment of closed houses include having control/surveillance workers commence activities at 06.00 hours on weekdays, to work at weekends or during school holidays, or as a last resort to invoke court orders against householders harbouring Ae.aegypti.     

Toxicite a long terme d'un insecticide organophosphore (fenthion) chez le mollusque Lymnaea stagnalis L.

A chronic intoxication with fenthion was induced in adult and young snails. The fecundity was only reduced by the concentratration of 4 ppm in adults. In the snails intoxicated by fenthion from hatching the shell growth and the fecundity were both reduced from a concentration of 2 ppm. Above 2.15 ppm the rearing of young snails was not possible.

     

Distribution and insecticide resistance of the plague flea Xenopsylla cheopis in Maharashtra State, India

Distributions are reported for commensal rat fleas, predominantly Xenopsylla cheopis (Rothschild), in the State of Maharashtra, India, including the city of Bombay, during 1965-80. The X.cheopis flea index was high in most parts of Maharashtra, but low in Bombay. Rattus rattus Linnaeus is the principal host of X.cheopis, but the host range includes Bandicota bengalensis Gray, Golunda ellioti Gray, Mus musculus Linnaeus, Rattus blandfordi Thomas, R. norvegicus Berkenhout, Suncus caerulaeus Lerr, S. murinus Linnaeus and Tatera indica Hardwicke. X.cheopis was found to have high degrees of resistance to DDT, malathion and fenthion, tolerance to gamma HCH (= gamma BCH) but susceptibility to dieldrin. This insecticide resistance situation may contribute to the high flea indices prevailing in the state, with consequent risks of plague outbreaks. Two other species of rat flea, X.astia Rothschild and X.brasiliensis (Baker) were found to be less common than previously recorded. Their apparent replacement by X.cheopis is tentatively attributed, at least partly, to the selective advantage of insecticide resistance in the latter species.     

Effect of fenthion treatment on larval densities of insecticide-resistant Culex quinquefasciatus in an urban area of Sri Lanka

Abstract. In Sri Lanka the national Anti-Filaria Campaign (AFC) has routinely employed fenthion since 1974 for larvicidal control of Culex quinquefasciatus , the vector of Bancroftian filariasis in urban areas, where this mosquito breeds prolifically in polluted waters. During 1994 the efficacy of AFC fenthion treatment against organophosphate-resistant Cx quinquefasciatus was investigated at Dehiwela, near Colombo.
The AFC target rate of fenthion application was 1 mg a.i./l, but the actual concentrations of fenthion in freshly treated pits ranged from 0.64 to 63.2 mg a.i./l. There was significant suppression of larval densities in treated soakage pits, the predominant breeding site of Cx quinquefasciatus , although the mosquito population was 6-fold resistant to fenthion at the LC_W level. Production of pupae was almost completely prevented in soakage pits which were sprayed weekly with fenthion, indicating that adult mosquito emergence from this source was minimal. The rapid decline in concentration of fenthion detected in the water of soakage pits indicated that a weekly treatment schedule is essential for effective control. With the rapid recolonization of treated sites, the weekly schedule must be strictly implemented in order to achieve control of resistant larvae. Fenthion activity levels detected in treated pits suggest that a 7–10 day schedule of retreatment would completely suppress susceptible Cx quinquefasciatus.     

DETRIMENTAL EFFECTS OF FENTHION (QUELETOX® UL), USED TO CONTROL RED-BILLED QUELEA (QUELEA QUELEA), ON RHEOPHILIC BENTHIC MACROINVERTEBRATES IN THE ORANGE RIVER

Summary

The relative abundance of rheophilic macroinvertebrates in the Orange River was assessed before and 15 hrs after two aerial applications of fenthion (QUELETOX® UL) above roosting sites of the red-billed quelea (Quelea quelea). The first treatment had no detectable effect on benthic macroinvertebrate abundance, whereas the second treatment caused mortality among at least 17 taxa (over half the taxa present). The most sensitive species were nymphs of the mayflies Baetis glaucus and Tricorythus discolor, followed by larvae of the midge Rheotanytarsus fuscus. Fenthion had no detrimental effect on the population densities of the mayfly Afroptilum excisum.

The results of this study warn of the dangers of fenthion in water supplies. It is suggested that alternative methods of quelea control along the Orange River should be sought.