The Fumigation Of Ethyl Formate To The Important Insects And The Effect On Two Enzymes

This paper studied:(1) the effect of the treatment time,temperature,relation humidity and concentration of pharmacy to ethyl formate (EF) against Tribolium castaneun(Herbst),Rhyzopertha dominica (Fabricius) and Sitophilus zeamais(Motschulsky) with absence of grain;(2) the effects of temperature,concentration of pharmacy,relative humidity and grain m.c. to the application of EF against the three insects in the sealed desiccators with wheat,rice and corn,the penetrability of EF in grain,and the adsorbability of grain to EF;(3)the effects of EF and formic acid to esterase,AChE and esterase zymogram of the three insects.It could achieve the perfect efficacy of fumigation with certain doses of EF exposed 24h in a sealed system with absence of grain,fumigation time was extended to 72h fumigation effects were not significantly different.The efficacy of fumigation in a relatively low temperature(16℃) was better than in a relatively high temperature. The mortalities of the three insects at 16℃had significant difference from that at 24℃and 32℃(p<0.05). There were no significant impacts to the effect of the relative humidity on EF with absence of grain, the mortalities of the three insects in 35%r.h.,60%r.h. and 85%r.h. were no significant different.The LC50 values of T. castaneun,R. dominica and S. zeamais were 25.97μl/L,12.50μl/L and 7.45μl/L, respectively,after EF applied for 24h at 24℃.The results showed that the penetrability of EF in corn was the best,wheat was the second,and rice was the worst. The higher temperature can increase the penetration of EF in the grain,the mortalities of S. zeamais and R. dominica under the rice were above 92% after 80mgL-1 EF applied for 72h at 24℃and 32℃,significant higher than the 29.72% and 5.62% at 16℃.The higher r.h.could increased the efficacy of EF,the mortalities of S.zeamais and R.dominica on the top of corn were above 90% after 80mgL-1 EF applied at 24℃,r.h.35%,60% and 85%,the mortalities of S.zeamais and R.dominica under the corn were 96.80% and 86.33% at r.h.85%,which that significant higher than at r.h.35%,60%.The higher m.c.of grain will increase the adsorption of grain to the EF,with more than 12% of grain m.c.,mortalities of S.zeamais and R.dominica under the corn were found below 20% even higher r.h.60% and 85% were used.The results of the acitivity of enzyme showed that it was no inhibition under the ethyl formate to S.zeamais'esterase and AChE in vitro,there had inhibition under the formic acid which that EF decomposed in the insect body to the AchE of R.dominica and S.Zeamais,and the esterase of the three insects.But the I50 of formic acid to esterase and AchE were much higher than the LC50 of the ethyl formate to the three insects.The results of non-denaturing PAGE showed that there had inhibition under the higher concentration of formic acid to the three insects,it showed that the inhibition formic acid to the AChE and esterase of the three insects was weak.