| Lasioderma serricome (Fabricius) is one of the most serious stored-tobacco pests during tobacco storage. As one of botanical pesticides, plant essential oil has the strong activity of fumigation,antifeedant,contact toxicity and repellent, and it is used as fumigants or fumigation agents has become one of the directions of stored-tobacco pest control.On the basis of preliminary work in the laboratory, bioactivity of natural product LC against L. serricome was further studied. UF-resin was used to encapsulate essential oil of natural product LC and a formulation of 25% natural product LC capsule suspension (CS) has been successfully formulated on the basis of screening the biological activity. Some theoretical value and application of the results are achieved.1. The results of bioassay show that natural product LC had good bioactivity against L. serricome. After the treatment of 24 h, the emendation death rate of adults and larvae of L. serricome are 95.65% and 88.33% under 30°C and at the dose of 160 ul/ml and 320 ul/ml. After the treatment of 24 h, 48 h, and 72 h and at the dose of 8 ul/ml and 4 ul/ml, the average repellent rate of natural product LC against adults and larvae of L. serricome are more than 80%. The inhibition rate of natural product LC to L. serricome was 100% at the dose of 8ul/g.2. Distribution of capsule was also investigated, and the results indicate that the optimal conditions are as follows: the active ingredient content of 25%, the rotating speed of 3000r/min, and pH of 3 at last.3. By screening agents of the type and quantity, wetting agent was identified at the dose of 5% of OX-713 and 5% of ABS-Ca, thickener at the dose of 2% of PVA, cryoprotectant at the dose of 5% of Glycerin.4. The parameters of the CS including the active ingredient content, the rate of capsule, density, suspension rate, dumping, dispersion and thermal storage stability were measured. The results show that the appearance was pale yellow viscous suspension, the active ingredients was above 25%, the capsule rate of active ingredients was above 80%, the density was about 1.1-1.2g/ml, the suspension rate was above 50%, the remnants of dumping and washing was less than 7% and 2%, the dispersion and thermal storage stability were good.5. Determination of release rate through residual method show the CS had slow-release function. After 1, 3, 5, 10, 15, 25 days, cumulative percentage of the release of CS was 27.12%, 36.08%, 43.83%, 62.95%, 75.06%, and 83.54% respectively. Those results were below cumulative percentage of the release of LC essential oil. The results of bioassays show that after 11 and 16 days, the CS had insecticidal effect of 85.17% and 68.85%, respectively, which can show its slow-release with biological effects.6. The result of CS against L. serricome in the actual warehouse of the simulation experiments indicated that it has strong treatment action. After 7 days the controlling effect reached respectively 58.9% at the concentration of diluting 200multiples of CS, which can be lower than the controlling effect of DDV. |
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