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Journal of Entomology

Year: 2015 | Volume: 12 | Issue: 2 | Page No.: 55-66
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Authors

H. Asimah

L. Albert

A.B. Idris

Keywords

Research Article

Application of Ethyl Formate as a Postharvest Fumigant for Dry Cocoa Beans under a Semi Commercial Trial

H. Asimah, L. Albert and A.B. Idris
Fumigant toxicity of Ethyl Formate (EF) against four major cocoa storage pests was carried out on a semi commercial trial of two metric ton of cocoa beans under sheet without forced air circulation. The EF with concentration from 76-380 g L–1 were studied against pupae, larvae and adult of Cocyra cephalonica and Ephestia cautella (moth) and Tribolium castaneum and Lasioderma serricone (beetles). These stored pests were inserted into a wire mesh tubes 6×1.5 centimeters (cm) and then arranged in a 25×2.5 cm polyethylene tubes and then inserted inside gunny sacks and exposed to the EF gas for 40 h with surrounding temperature and relative humidity (R.H.) recorded throughout the trial of 26±0.3-34±0.4°C and 65±0.4-91±0.2%, respectively. While, the temperature inside the tarpaulin was between 24±0.3-30±0.2°C and the R.H. as minimum of 42±0.4% and maximum of 63±0.3%. The result indicated that complete mortality for all stages of insects was detected at minimum concentration of EF (190 g L–1). Different stages and insect species gave difference response to the toxicity level of EF. However, the LC99 value for larvae and pupae of all stages of four insects tested showed no significant different among species except for adults of T. castaneum and L. serricorne. For LC50 value for larvae of L. serricorne, E. cautella and L. serricorne pupae are relatively more susceptible to EF than other two species. The estimated probit regressions were well fitted to the response as the chi-square values for larvae, pupae of four pest and two adults pests tested were not significant at 5% level of confident. The residue of EF was not found in whole beans, nibs and cocoa beans. As such the EF was successfully developed as a fumigant for treatment of pests control for dry cocoa beans.
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