Research On Preparation Of Drosophila Melanogaster Repellent Microcapsules

Blueberry is a kind of perennial small berry fruit tree with health benefits such as liver protection,prevention of cardiovascular disease,anti-cancer,antioxidant and anti-ageing.Since the blueberry was introduced in Guizhou in 2000,its cultivation scale has made great progress so that Guizhou became the largest blueberry-product province in China.However,insect pests had been a serious impact on the blueberry diseases,and the Drosophila spp.is one of the most threatening pests.The present study showed that physical control is not necessarily effective enough,and chemical control affects rapidly and efficiently on Drosophila spp.,but it will threaten the natural environment and human health by long-term use.Plant essential oil compounds can affect the behaviour of insects and are safe repellent active ingredients.However,these compounds are extremely volatile and degradable under natural conditions.Thus,there is an effective and environmental friendly measure defined microcapsule technology that is embedded repellent into microcapsule for environmental protection and control of Drosophila spp..Drosophila melanogaster,one of the Drosophila spp.and also the main insect that harms blueberry orchards in Guizhou,was the research object to explore the repelling effects of plant essential oil single-component compounds,their different combinations and different proportions of mixtures on Drosophila melanogaster.Their optimal combination was chosen as the internal material and the gelatin and chitosan as the external material of the microcapsules by the complex coacervation method to study the repelling effect of the microcapsules on Drosophila melanogaster.The main conclusions were as follows:1.The Y-olfactometer assay showed that among the 10 kinds of plant essential oil singlecomponent compounds,Dipentene and citronellal had the best repelling effect on the female flies,and both two essential oil repellent effects were better in the concentration of 10%～50%and it was positively correlated with the concentration.30% Dipentene and 30% citronellal were mixed in a volume ratio of 5:5,which showed a significantly repelling effect on female flies,and the average repelling effect was 79.68%,so the mixed repellent of Dipentene and citronellal under this condition was selected as the internal material of repelling microcapsules.2.The mixed compounds were embedded by the complex coacervation method,and the results showed that the emulsifier HLB value was 13,and the volume ratio of the emulsifier and the mixed compounds was 1:2,which made a relatively stable emulsion as internal material.The mass ratio of gelatin and chitosan was 5:1 by turbidimetry to prepare external material.By the single factor test results,the encapsulation rate is used as the evaluation index.The response surface design test for optimizing the process,and this result was shown as follows:the internalexternal ratio is 1:1.934,the external material concentration is 0.963%,the stirring rate was611.236 r/min,the reaction time was 30 min,and the curing time was 2 h.Under this condition,the microcapsules encapsulation rate reached 74.315%compared with the computer calculated maximum.3.For characterization of repellent microcapsules,the electron microscopy results showed that gelatin/chitosan could successfully encapsulated the core material with a particle size between 40 and 103 μm,which had a protective effect on the core material.Fourier transform infrared spectroscopy results showed that Dipentene and citronellal were successfully encapsulated by gelatin/chitosan.The thermogravimetric analysis showed that the prepared microcapsules had a certain influence on the protection of Dipentene and citronellal,and could have a slow release effect on them.4.The indoor test results showed that all repellent microcapsules with different qualities had repelling effects on Drosophila melanogaster and the repelling rate was significantly positively correlated with the increase of the quality,and also the drug effect time was prolonged.The repelling microcapsules with a mass of 0.1 g reached the highest repelling rate(21.98%)at 72 h,but 0.2 g and 0.3 g achieved the highest repelling rate at 96 h,which were33.99% and 37.82%,respectively.Besides,the repellant had the highest repelling rate at 24 h(39.52%).The repelling rate of the repellent microcapsules to Drosophila melanogaster was lower within 24 h but the rate slowly increased after 24 h.On the contrary,the repelling rate of the repellent to Drosophila melanogaster after 24 h decreased rapidly.This study showed that the repellent microcapsules can prolong the release time of the repellent,thereby advancing the repellent effect.