Fumigation Toxicity Of Essential Oils From Zanthoxylum Schinifolium Sieb. Et Zucc And Zanthoxylum Bungeanum Maxim And Ethyl Formate Against Callosobruchus Chinensis (L.) And Callosobruchus Maculatus (F.)

Cowpea weevil(C.maculatus F.) and southern cowpea weevil(C.chinensis L.) are two kinds of important stored product insect pests.Both pests can cause great lose of stored bean,the female lay eggs on the surface of the beans,after a very short period(just a few days),the larvae hatched into the beans.Most of their life-time,the pest stayed inside and grow into pupae while take the bean as their food.When adults emerge from the beans,females lay eggs on the surface and begin another cycle of damage to the beans.The life cycle of the two kinds of weevil is relatively short(within 30 days),and the damage caused by weevils is great.In this thesis,ethyl formate(EF) and essential oils from Z.schinifolium and Z.bungeanum are used to test their fumigation toxicity against these two pests.Data shows that the three fumigants individually can control eggs,larvae,pupae and adults of these two bruchidaes.Combination of EF and Z. schinifolium essential oil also can control adults of C.chinensis as well.1.Fumigation toxicity of essential oils against C.chinensis and C. maculatus.The two essential oils can control the three different developmental stages(egg stage,inside stage and adult stage) of the bruchidae.Under the same concentration of 130μL/L of Z. schinifolium essential oil,12hour fumigation can cause adult corrected mortality of 62%while 60hour fumigation can cause adult corrected mortality of 92%,similar results were observed when fumigated with Z.bungeanum essential oil.This indicates that fumigation time can affect the toxicity of essential oils significantly;lengthen the time,more pests will be killed.Different treatment temperature also affects the fumigation toxicity significantly.At 19℃, fumigation result in the lowest corrected mortality while at 34℃,corrected mortality are the highest with both essential oil.These results indicate that higher fumigation temperature with essential oils may kill more pests.2.Fumigation toxicity of EF against C.chinensis and C.maculatus.EF can kill the two bruchidaes in all three stages with low concentrations.EF shows its fumigation toxicity so rapidly and 3hour exposure and 60hour exposure of adults of C.chinensis result in no significantly difference.This indicates that EF can show the fumigation toxicity in a very short period.Temperatures also affect the toxicity significantly.Corrected mortality changes while fumigation temperature change.19℃,22℃and 25℃result in higher mortality while high temperature as 29℃and 34℃result in lower mortality,which Indicate that EF will be more toxic when temperature is low.3.Fumigation toxicity of combination of essential oil and EFCo-toxicity coefficient of essential oil with EF is tested.Mixtures are as follows:Essential oil:EF(Volume:Volume) =19:1,9:1,5:1,2:1,1:1.CTC values are 344,303,275,210 and 206, respectively.All mixture of fumigants showed synergetic effects indicates that essential oils with EF have potential to be more toxic when mixed together.4.Risk assessment of C.chinensis resistance to EFThe resistant risk of C.chinensis to EF is assessed using the realized heritability(h~2) in quantitative genetics.The realized heritability of resistance of C.chinensis to EF is 0.0765 under the selection pressure of the average mortality of 62%.Under the condition of this pressure,the selection of 75 generations should be conducted if the resistance of C.chinensis to EF amounted to 10 fold.