Study On The Biological Characteristics And Control Of Stephanitis Chinensis Drake

Stephanitis chinensis Drake,also known as tea web bug,beginning the major pest in the southwestern tea area.The insect has the characteristics of small size,easy breeding,easy spreading,no natural enemies,easy to outbreak,multiple hazards and is difficult to control.The prevention of S.chinensis is still mainly chemical control for the moment,which is easy to cause the problems of environmental pollution,over-standard pesticide residues,increased pest resistance and injuried natural enemies of pests.In this paper,the biological characteristics of S.chinensis were studied.At the same time,field trials were carried out to control S.chinensis with a new botanical insecticide-30%tea saponin.The main contents and results of this paper are as follows.1.The study on the biological characteristics of S.chinensis.Through indoor rearing and field monitoring,the morphological character,life habits and occurrence regularity of S.chinensis were studied.The results showed that the S.chinensis oviposit in mesophyll tissue and prefers to oviposit in the middle of leaves and at both ends of veins.The nymphs have 5th instar:1st instar nymphs have no spines,2nd instar nymphs have prominent spines but no wing buds,3rd instar nymphs have slightly prominent wing buds,4th instar nymphs have wing buds at the front of 1st abdominal segment,5th instar nymphs have white wing buds at the front of 4th abdominal segment.Adults have wings but flight ability is weak.Males are slightly smaller than females.The abdomen of females is hypertrophic and oval,while males have relatively slender abdomen.In this experiment,two generations of a year old S.chinensis overwintered in mature leaf tissue of middle and lower parts of tea bushes with eggs.The first generation’s incubation period in early and middle April.In early and mid-May,nymphs began to flourish.The second generation of eggs hatched from the beginning of September to the end of October.The eggs hatched very irregularly and entered flourishing period of nymph in the middle of September.In the whole year,the first generation of eggs produced neatly and the population density was high,which was 3-4 times higher than the second generation.The maximum hatching rate of nymphs was 63.88%,the emergence rate was close to 100%,and the emergence period was about 15 days.2.The study on predation of Evarcha albaria on S.chinensis.The predatory function and disturbance response of E.albaria to S.chinensis were studied.The predation of E.albaria increased with the increase of the density of S.chinensis.Therefore,the functional responses of female and male spiders to nymphs and adults of the S.chinensis were in accordance with Holling type II.The control ability of E.albaria to nymph of S.chinensis was greater than that to adults.The fitting equation of spider’s response to self-density interference is as follows:male spider:E=2.1782P^-0.897;female spider:E=2.5741P^-0.989.T-test showed that the interference coefficient m between female spiders and male spiders was very significant（t=15.15,P<0.01,t=43.91,P<0.01）.3.The indoor toxicity determination of 30%tea saponin solution against larvae of S.chinensis and spiders.The toxicity of 30%tea saponin to 2-3 instar nymphs of S.chinensis was determined by leaf dipping method.The toxicity of 30%tea saponin to Agelena difficilis and E.albaria was determined by contact residue.The avoidance effect of 30%tea saponin on A.difficilis and E.albaria was also studied.The results showed that 30%tea saponin solution had toxic activity to nymphs of S.chinensis（3rd instar and below）.After 48 and 72hours of treatment with tea saponin solution,medium lethal LC50（unit:g/L）for nymphs were 55.66 and 43.11.30%tea saponin have no toxic activity against A.difficilis and E.albaria.30%tea saponin and its mixture had no repellent effect against A.difficilis and E.albaria.4.The field control efficiency of 30%tea saponin solution against S.chinensis and the effect on spiders in tea garden.By setting 30%zoloxamide（3000×）and 2.5%bifenthrin（1500×）as chemicals control,a field plot experiment of 30%tea saponin on S.chinensis and its effect on spiders in tea garden of Enshi Academy of Agricultural Sciences was conducted.The results showed that 3 day later,the control effect of 30%tea saponin and 0.3%matrine water began to improve,especially their mixture reaching 80.45%.There was no significant difference between zoloxamide and bifenthrin（p=0.33,p=0.804）.7-14 days after treatment,the control effect of 30%tea saponin and 0.3%matrine both reached 70%,and the control effect of their mixture remained above 80%.14 days after treatment,the control effect of Bacillus thuringiensis solution was 67.44%.There were no significant differences on spider species and number in tea garden treated with 30%tea saponin and 0.3%matrine,their mixture and Bacillus thuringiensis emulsifiable.