The Interaction Between Frankliniella Occidentalis (Thysanoptera: Thripidae) And Leguminous Vegetables

Western flower thrips(WFT),Frankliniella occidentalis(Pergande)(Thysanoptera:Thripidae),is one of the most important and widespread pests and causes damage to over 500 species of vegetables and ornamentals through direct feeding damage and disease vectoring.Many researchers around the world have done the systermatic reseach on it.The pest was firstly recorded in China mainland in June 2003 and called invasive species.Franldiniella occidentalis has spread in Beijing,Yunan and Shangdong areas,and researchs on it is beginning.In the invegistation,Thripidae pests have caused the serious damage on vegetable in Guiyang,Especially,it was causing serious threat for the production of leguminous vegetables.The dominant specises was dentified as Frankliniella occidentalis by authoritative scholar.The present dissertation focused on preliminary study on the interaction of F.occidentalis and leguminous vegetables,including the effect of host plants and temperature on the development,survival rate,reproductive model.Host plants selectivity and the changes of physiological indices were assessed when the host plants damaged by F.occidentalis.The results were summarized as follows:1,The survey of thrips species on leguminous vegetables of Huaxi district of Guiyang city and the morphological characters of the dominant specisesThrough investigation,we found there were 7 species of thrips which damaged the leguminous vegetables on Huaxi district,The dominant specises was the western flower thrips according to the population and damage index.The morphological characters and identification characters were described in this paper.2,Effect of host plant on development and survival rates of F.occidentalisHost plants had great influence on the average development periods of F.occidentalis.It was significant difference among the average development periods of western flower thrips feeding on different host plants at the same temperature conditions.For example,The average development periods of the 1st instar nymph was longer when feeding on the leaves of Glycine max(soybean),the leaves of Vicia faba(broad bean),and the pod of Phaseolus vulgari(kidney bean) at 19℃,but there was no significant difference among them,.While the average development periods was shorter when feeding on the leaves of Vigna sinensis(cowpea) and Phaseolus vulgari(kidney bean) at the same temperature,and there was no significant difference between.them too.But there was significantly different between the former and the later.The influence of host plants on the survival rate was not obviously.3,Effect of temperatures on development and survival rates of F.occidentalisThe total developmental periods of the egg,1st instar nymph,2nd instar nymph,prepupa,pupa and the immature of the thrip at the temperature of 19-31 decreased when the temperature increased from 19℃to 31℃under five different host plants.Based on the linear regression method,the threshold development temperature and effective accumulated temperature were calculated.Usually the survival rates of the thrip increased with the temperature increasing at the range of 19℃to 25℃,but the survival rate was the lowest at the temperature of 31℃.4,Reproductive models of F.occidentalisF.occidentalis had two reproductive models,which were bisexual reproduction and Parthenogenesis. The type of Parthenogenesis was androgenetic parthenogenesis.There were both female and male offspring under bisexual reproduction.There was highest female male ratio(♀/♂) when fed on the pod of kidney bean.The oviposition was biggest when fed on the pod of kidney bean,while there was not significant difference among other three host plants.5,The host plant selectivity of F.occidentalisFour Leguminous Vegetables were selected to test host plant selectivity of F.occidentalis,which were Glycine max,Vicia fab,Phaseolus vulgari and Vigna sinensis.Host plant selectivity was assessed by Olfactometer of Y shape.Volatile played an important role in the response when the thrips looking for host plants.F.occidentalis was attracted by odors from host plants,while thewre was no siginificantly different among four host plants.The host plant selectivity of F.occidentalis was studied by the method of leaf disc.The results showed significant tendency of F.occidentalis to different host plants in two different densities,there was highest density in Phaseolus vulgari,and lowest number in Vicia faba.6,The change of physiological index of host plant infected by F.occidentalisThe physiological indexes were tested in both healthy and infected of host plants.Infection by F. occidentalis decreased the chlorophyll content and photosynthesis of the leaves of kidney bean,so affected growth and accumulation of substance in kidney bean and finally reduced kidney bean yield.The content of total sugar and the soluble sugar increased with the increasing of damage,which indirectly increased the possibility of damage.