The Effect Of Ethyl Formate On Tiny Pests

This paper studied fumigation lethal effect of ethyl formate on three common Laemophloeidae(Cryptolestes ferugineus,Cryptoleste spusilus Schnherrand Turkey turcicus)and two typical psocids(Liposcelis bostrychophila and Liposcelis entomophila)at different fumigation temperatures and durations.The fumigation toxicities ofethyl formateon different insects were compared.In the simulated warehouse,fumigations were tested to kill these insects with and without grains.Theconcentration change of ethyl formatein different positions of simulated warehouse were determined.Besides,the residues of ethyl formate in grain were detected.The results are shown as follows.Ethyl formate showed better fumigation lethal effect on the three Laemophloeidae.At fumigation temperature of 25oC,when fumigation time was 24 h and fumigation dose was 33 μL/L,corrected mortality of the three Cryptolestes were 74.7%,60.4% and 65.2%,respectively;at the same temperature,when the fumigation time was 48 h and fumigant concentration is 30 μL/L,mortality rates of the three Cryptolestes were 78.3%,56.4% and 70.5%,respectively.At fumigation temperature of 25 oC and fumigation time setting at 24 h,LC50 of ethyl formate to three insects were 28.44,30.68 and 29.70 μL/L,respectively;at the same temperature and fumigation duration setting at 48 h,LC50 were 25.06,28.30 and 25.65 μL/L,respectively.For 24 h of fumigation,when fumigation temperature was set at 20 oC,LC50 to the three tested insects were 26.13,27.27 and 26.50 μL/L,respectively;when temperature was setat 25 oC,LC50 data were 28.44,30.68 and 29.70 μL/L,respectively;at temperature of 30 oC,LC50 data were 33.53,36.60 and 35.72 μL/L,respectively.Ethyl formate had lethal effects on both the two psocids.When the fumigation time was 24 h,at the high dose of 33 μL/L fumigation,corrected mortality of the two psocids were 76.7% and 86.1%,respectively;when the fumigation time was 48 h and fumigant concentration was 30 μL/L,corrected mortalitiesof the two psocids were 89.3% and 97.5%,respectively.With the increase of fumigation temperature,the mortality rate of the two species of ticks decreased.For these two species ofpsocids,the LC50 values after 48 h of fumigation were lower than 24 h.For 24 h for fumigation,LC50 values to the former psocid were 21.91,26.90 and 30.03 μL/L at fumigation temperatures of 20 oC,25oC and 30oC,respectively;this parameterto the latter type were decreased to 21.71,25.72 and 27.72 μL/L,respectively.In the simulation experiment,fumigating effect was investigated in the silo without grain atethyl formate concentration of 70g/m3.Results showed that the death rates of five insects reached100% in silo without grains.The concentrations of ethyl formateat three layers were kept stable at 4-6h.When the concentration of each layer is stable,the ethyl formate concentration in different sitesof the warehouse is: the lower layer > middle > upper layer.The simulated warehouse was fed with different wheat to evaluate the fumigation effect at ethyl formate concentration of 70g/m3.For the low grain feeding height(0.5m),death rates of all tested insects in the middle and upper layers reached 100%.As the height of grain increased,the mortality of the upper layer remained at 100%,but the survival rate of insects gradually increased.In the silo,the ethyl formate concentration decreased as the position varied fromupper layer to lower layer.During the fumigation process,the concentration of ethyl formate in the upper layer was decreased rapidly at the beginning period,but then decreased gradually as fumigation extended.The concentration of ethyl formate was very low and remained stable at the lower layer of the warehouse.After fumigation,the residual ethyl formate content of the grainshowed a downward trend as the position varied fromupper layer to lower layer,and the difference between the center and the wall at the same height was minor.