Influence of posttreatment temperature on the toxicity of pyrethroid insecticides to susceptible and resistant larvae of the Egyptian cotton leafworm,Spodoptera littoralis (Boisd.)

Abstract

188blocking effect directly on the muscle. This effect is significantly inferior to the inhibitory effect observed when the muscle is stimulated via the nerve. These observations suggest that the target for these compounds is to be found in the nerve muscle junction. The effect of the analogues III and IV on the twitch tensions is of the same order of magnitude as demonstrated for I and II. It is therefore suggested that the mode of action of HI might correspond to that of I and II. The mode of action of IV seems to be more complex since this compound is the only one tested that shows an inhibitory effect on the action potential in the frog nerves. The effects of the open-chain analogues on the in vitro preparations lend no support to the hypothesis that the dithiolane moiety is the active principle and that active analogues are metabolized into dithiolanes 15. Experientia 40 (1984), Birkhguser Verlag, CH-4010 Basel/SwitzerlandThe effect level for charatoxin compares well to that of the structurally related nereistoxin on the sartorius nerve muscle preparation as it appears from figure 2. Since both compounds show insecticidal potency with similar symptoms of intoxication 6 it is indicated that further studies on the insecticidal properties of charatoxin analogues may prove fruitful.Many questions remain to be answered regarding the precise site of action of charatoxin and its analogues. The results presented here clearly point at the cholinergic transmission as the region of action. But nothing is known about the specificity of the observed inhibition. Further studies on e.g. binding affinity to acetylcholine receptors, and a more detailed electrophysiological investigation of the effect on the membrane potentials should therefore be carried out.Summary. The organophosphorus insecticides chlorpyrifos, leptophos, and phosfolan and the carbamate methomyl was found to be more toxic to larvae of a susceptible strain of Spodoptera littoralis (Boisd.) when the posttreatment temperature was increased from 20 to 35 ~ In contrast, the pyrethroids permethrin, fenvalerate, deltamethrin, cypermethrin, and flucythrinate were more toxic at 20 ~ than at 35 ~ This effect was more pronounced in the pyrethroid-resistant strains. Evidently, resistance levels were reduced at low temperature. However, the application of piperonyl butoxide or DEF in combinations with the tested pyrethroids on R-strains resulted in reducing the effect of temperature.Several factors influence insecticide toxicity, one being temperature. It has been shown that the toxicity of natural pyrethrins and DDT correlated negatively with increasing posttreatment temperature ~-3. On the other hand organophosphates have shown a positive temperature coefficienff '4'5. Carbamates were reported to have a slightly 67 negative temperature coefficient', although methomyl manifested greater toxicity at higher temperatures in some insect species 4'8'9. Recent developments in pyrethroid chemistry have resulted in synthesis of relatively stable compounds with high toxicity ...

Whole sediment toxicity identification evaluation tools for pyrethroid insecticides: III. Temperature manipulation

“…A similar mechanism was proposed for the observed inverse temperature effect on pyrethroid toxicity to a leafworm, Spodoptean littoralis [37], and a temperaturedependent change in pyrethroid metabolism has also been seen in rainbow trout [35]. Chironomus dilutus readily biotransformed permethrin at both temperatures, however, the biotransformation rate (k m ) at 13ЊC was half that at 23ЊC.…”

An evaluation of the effects of deltamethrin on two non-target lizard species in the Karoo, South Africa

“…Johnson (1990) has shown that deltamethrin is more effective at higher body temperatures in two species of grasshoppers, Camnula pellucida (Scudder) and Melanophus bivittatus (Say), but this relationship may be reversed in other species (e.g. Riskallah, 1984;Grafius, 1986). However, since the selected body temperatures of the two lizards species that we investigated differ by less than 13C (Huey et al, 1977), it is unlikely that temperature difference is the main cause of the difference in the decrease in abundance.…”

Synergism of insecticides provides evidence of metabolic mechanisms of resistance in the obliquebanded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae)

“…This implies that metabolic detoxification by monooxygenases, esterases and glutathione/glutathione S ‐transferases may all be involved in imparting chlorpyrifos resistance. Chlorpyrifos was synergized by both PBO and DEF in S littoralis 39 and DEF increased the toxicity of chlorpyrifos in H virescens , explaining its tolerance 40. Increased levels of monooxygenase activity as well as increased hydrolysis of chlorpyrifos oxon were mainly responsible for resistance to chlorpyrifos in B germanica 41.…”