Study On Insecticidal Activity Of Cantharidin And Its Analogues

Cantharidin is a natural sesquiterpene toxin from Meloidae and it have Iinsecticidal activity. In order to ascertain the insecticidal spectra and mode of action of the cantharidin, and find the cantharidin analogues which have insecticidal activity. The insecticidal activity of cantharidin and 1.0% cantharidin EC on thirteen species of insect pests was tested by different laboratory bioassay methods in this study. Our laboratory had synthesized eight kinds of cantharidin analogues, which insecticidal activity was tested by bioassay methods in this experiment. One kind of fly-luring toxicant bait, which was composed of muscalure, cantharidin and sugar-containing vector was prepared, and the effect to trap and kill houseflies was determined in the different times. The results were as followed.1. Cantharidin has wide insecticidal spectrum and various action mode. Its LC50 values of stomach toxicity to housefly adults were 781.90 (48h) and 397.22 (72h) mg/L. Its LC50 values of stomach toxicity against third-instar larvae of armyworm were 278.64 (24h) and 116.09 mg/L (48h), and the LD50 values of contact toxicity were 0.47 (24h) and 0.37μg/insect (48h), and the AFC50 value of selective anti-feed activity was 190.77 mg/L (24h), and the AFC50 values of non-selective antifeedant activity were 37.53 (24h) and 47.94 mg/L (48h). Cantharidin has certain ovicidal activity to the eggs of armyworm, when the concentrations of cantharidin were 500 and 1000 mg/L, the average hatching rates of the eggs of armyworm were 51.81% and 64.49%, respectively. Its LC50 value of stomach toxicity against fourth-instar larvae of Pryeria sinica was 182.41 (48h) mg/L, and the LD50 values of contact toxicity were 0.084 (24h) and 0.049 (48h)μg/insect. Its LC50 values of contact toxicity against third-instar larvae of Culex pipiens were 100.23 (24h), 54.9 (48h), 35.54 (72h) and 32.01 mg/L (96h), respectively. Cantharidin had obvious stomach toxicity and contact toxicity to adult corn weevils, also showed certain repellent activity and population restriction.2. 1.0% cantharidin EC showed high aphis-killing activity and acaricidal activity. The LC50 values for contact toxicity of 1.0% cantharidin EC to Myzus persicae, Macrosiphoniella sanborni, Hyaloptera amygdali, Lipaphis erysimi and Macrosiphum roswomm after 12h were 19.52, 15.84, 16.63, 25.94 and 26.20 mg/L, respectively, and cantharidin had certain systemic activity to vegetable aphid. The LC50 values for contact toxicity of 1.0% cantharidin EC to Tetranychus cinnabarinus, Penthaleus major and Tetranychus viennensis after 12h were 8.26, 13.38 and 8.46 mg/L, respectively.3. Cantharidin poison bait had excellent effect to trap and kill housefly adults of 3 to 5 day old. When cantharidin content reached 0.1%, the killing-fly rate of poison bait, after 48h and 60h, reached 81.04 % and 95.78%, respectively.4. This experiment tested the insecticidal activity of eight cantharidin analogues, which were synthesized by our project team. The results showed that norcantharidin had not only stomach toxicity but also contact activity to third-instar larvae of Plutella xylostella, when the highest concentration of stomach poison was 4000 mg/L, the average death rate of Plutella xylostella was 86.67%, when the maximum dose of contact poison was 4μg/insect, the average death rate of treated Plutella xylostella were 73.33% and 83.33% respectively after 24h and 48h. Norcantharidin also had weak contact activity to adult corn weevils. Cantharidin-acid had obvious contact activity against third-instar lavae of Plutella xylostella.