The Evaluation Studies On Insecticidal Effect Of Food-grade Inert Dust

In this paper, the influence of different factors on insecticidal effect of new food-gradeinert dust which called No.4to the main stored-grain insects Rhizopertha dominica(Fabricius), Cryptolestes ferrugineus (Stephens) and Oryzaephilus surinamensis (Linné),Tribolium castaneum (Herbst) was tested with surface treatment and grain mixture treatment.To provide technical support for the application and further reveal the Insecticidal Mechanism.The results were as follows:1. Bioassay test of No.4to four kind of stored-grain insect under different ambienttemperature by surface treatment shows that the influences of temperature were different todifferent species. To set the temperature level as20℃,25℃,30℃,35℃. The insecticidal effectto R.dominica O. surinamensis C.ferrugineus and T.castaneum adults was positive correlationwith temperature. For R.dominica, temperature has a positive correlation with insecticidaleffect,but at30℃the time which total insect were killed was fluctuating. For the adults ofT.castaneum, temperature has a synergistic effect on the insecticidal effect, but the30℃insecticidal effect of No.4is the worst. At low temperature such as20℃,25℃lethal effectwas better than30℃.2Bioassay test of No.4to four kinds of stored-grain insect under different ambientrelative humidity by surface treatment shows that increased relative humidity reducing theeffectiveness of inert dust. To set the relative humidity level as45%,65%,85%,100%.3Bioassay test of No.4to four kinds of stored-grain insect with different wheat moisturecontent by grain mixture treatment shows that increased moisture content reducing theeffectiveness of Food-grade inert dust. To set the moisture content level as10%,12%,14%,16%.4Bioassay test of No.4to adult of R.dominica and T.castaneum was by grain mixturetreatment. The result showed that when tempreture, relative humidity, dosage coexist, theoptimal combination to kill R.dominica was35℃,200mg/kg dosage, RH45%; forT.castaneum the optimal combination was200mg/kg dosage,25℃, RH45%. Whentempreture, moisture content, relative humidity, dosage coexist, the optimal combination tokill R.dominica was M.C.10%25℃,200mg/kg dosage, RH65%; for T.castaneum the optimal combination was200mg/kg dosage, M.C.10%,20℃, RH85%.Study the comprehensive effect of the various factors, i.e. ambient temperature,relative humidity (grain moisture content), dosage. The result also showed that: when multiplefactors exist, there is interaction between the factors. For R.dominica and T.castaneum, therewas a remarkable negative correlation between insecticidal effect and relative humidity andmoisture content, and a positive correlation between insecticidal effect and dosage.