Study On The Biological Activity Of 32 Plant Essential Oils Against Blattella Germanica

Blattella germanica has been listed as a worldwide household health pest due to its wide distribution,mixed diets and transmission of diseases,which seriously affects people’s life.Rapid breeding,strong adaptability and serious resistance to chemical pesticides increase the difficulty of controlling B.germanica.It is becoming a hot topic in many countries about how to effectively prevent and control B.germanica.Using plant essential oils to control public health insects is focus on mosquitoes,however,relatively few studies have been carried out using plant essential oils to control cockroaches.To obtain 1 or 2 kinds highly active plant essential oil,32 species of plant essential oils against 4th-instar male nymph of B.germanica were screened by using repellent,contact and attractant bioassay methods.The purpose of the research is to provide basic data for developing cockroach control agent with practical value and development prospects.The main results are as follows.1.Repellent biological activity of 19 plant essential oils against B.germanica was determined by the filter paper membrane method.The results showed that 19 plant essential oils had certain repellent activity against B.germanica.At the dosage of 1000 μg/cm²,the repellent rates of lavender essential oil,elsholtzia essential oil,wintergreen oil,photinia oil,Pinus massoniana leaf oil and houttuynia essential oil against B.germanica reached more than 60%in five minutes.Among them,the repellent rates of wintergreen essential oil and lavender essential oil on B.germanica 88.50%and 76.62%,respectively.The repellent toxicity(RD₅₀ values)of the above six plant essential oils against B.germanica were 154.590,218.634,223.989,233.325,472.859 and 492.179 μg/cm²,respectively,which were significantly lower than the control agent DEET(RD₅₀=650.404 μg/cm²).2.Contact biological activity of 20 plant essential oils against B.germanica was determined by the filter paper membrane method.The results showed that 10 plant essential oils had certain contact activity against B.germanica,such as wintergreen essential oil,elsholtzia essential oil and horseradish essential oil etc.At the dosage of 500 μg/cm²,horseradish essential oil and wintergreen essential oil had good contact toxicities against B.germanica,and the mortality rate of the tested insects within 72 hours were 95.83%and 79.17%,respectively.The contact toxicity(LD₅₀ values)of above two plant essential oils against B.germanica were 28.53 and 147.528 μg/cm²,respectively.Compared with the control agent cypermethrin(LD₅₀=7.845 μg/cm²),although the LD₅₀ values of horseradish essential oil and wintergreen oil were relatively high,horseradish essential oil is still deserved develop as cockroaches control agent due to its safety and control efficacy.3.Repellent synergistic effect of the combination of wintergreen oil and elsholtzia essential oil against B.germanica was studied.The results showed that the co-toxicity was 214.4 at the mass ratio of 1:1.41,and its value was greater than 200,showing a significant synergistic effect.At this ratio,the repellent effect of the combination of wintergreen oil and elsholtzia oil against B.germanica was the best,the RD₅₀ was 104.636 μg/cm².Therefore,the combination of wintergreen oil and elsholtzia essential oil has the potential to be developed as a repellent agent against cockroaches and deserves further study.4.Formulation of 22%horseradish oil emulsifiable concentrate against cockroachs was developed.The specific formula is as follows:22.5%horseradish essential oil,1.5%agricultural emulsifier 500,7.5%agricultural emulsifier 602,68.5%sec-butyl acetate.And the quality test results conform to the relevant national standards（GB）.5.Contact activity of the 22%horseradish oil emulsifiable concentrate against 4th-instar male nymph of B.germanica was determined.The results showed that at the dosage of 10μg/cm²,the corrected mortality rate were more than 50%within 72 hours.According to the results of above,22%horseradish oil emulsifiable concentrate can be used to control cockroaches,however,its on-site killing effect and application technology are worth studying.