Artificial Breeding And Field Release Techniques Of Encarsia Formosa

Bemisia tabaci is a major invasive foreign pest globally.The increase harm to cotton,tobacco and vegetables in China,the control of Bemisia tabaci is more and more difficult.Bemisia tabaci is one of the most important pests on tobacco.The adults and nymphs suck tobacco juices and produce honey-dew to pollute tobacco leaves,which seriously affects the quality of tobacco leaves.The occurrence of Bemisia tabaci on a large scale in Shandong province has caused serious economic losses.For the control of tobacco whiteflies,it is important to choose biological control measures.The purpose of this study was to investigate the resistance of 11 tobacco varieties to whiteflies,and to carry out artificial breeding of Encarsia formosa on a large scale with "Zhongyan 100" as host plant,and through separation experiment of Bemisia tabaci and Encarsia formosa with 80 mesh insect net cages,the release tool of Encarsia formosa in tobacco field and vegetable greenhouse were designed,and the biocontrol work of releasing Encarsia formosa was carried out in field.The main results of this experiment are as follows:1.Resistance comparison of 11 tobacco varieties to Bemisia tabaciThe resistance of 11 tobacco varieties to Bemisia tabaci based on the occurrence of adult and nymphs of Bemisia tabaci,the result indicated that Zhongyan 100 was the most susceptible variety,and the dominant varieties resistant to Bemisia tabaci were NC89 and NC55.Dynamic investigation results during the growing period showed that the occurrence of Bemisia tabaci in all varieties was sporadic in June,the number increased obviously by July and the selectivity of different varieties began to appear,Zhongyan 100,Yunyan 87 and CF228 the most,and the selectivity to 11 varieties was more obvious in August.2.Artificial breeding technology of Encarsia formosa on a large scaleIn 2017,"Zhongyan 100" was used as host plant in the greenhouse of Zhucheng Tobacco Experimental Station for artificial breeding of Encarsia formosa which took place for three times and applies the circulation model of Zhongyan 100-whitefly-Encarsia formosa.The propagation results showed that the first time propagation was the best,the parasitic rate of the Encarsia formosa was 78.9%,the emergence rate of Encarsia formosa in the greenhouse was 88.5%,the emergence rate of Encarsia formosa in the field was 85.6%,and thetemperature and humidity of the first time propagation were most suitable for the reproduction of Encarsia formosa.The tobacco leaves were collected from the greenhouse and put into the self-made net cage for control.3.Separation experiment of Encarsia formosa and Bemisia tabaci with 80 mesh net cagesThe separation of Encarsia formosa and Bemisia tabaci with 80 mesh net cage showed that the flying-out rate of Bemisia tabaci was 1.15%,the mortality rate was 2.57%,and the flying-out rate of the Encarsia formosa was 87.91% and the mortality rate was 1.5%.Therefore,the 80 mesh insect proof net cage can effectively block the flying-out of adult Bemisia Tabaci,and does not hold back the flying-out of Encarsia formosa.Based on the results the release tool of Encarsia formosa in field were designed.4.Encarsia formosa release toolsThe release tool materials mainly included the iron rod,adjusting knob,PCR tube,three-way tube and 80 mesh insect proof net cage.The size of the tool is 25 cm×20 cm×15 cm,and there is a 80 mesh insect proof net(can use nylon gauze)around the cuboid frame,and one side of the net cage is designed a L-shaped zipper,to facilitate the putting and taking out of the tobacco.The adoption of this structure of field cage tool can not only ensure the release of Encarsia formosa while blocking the Bemisia tabaci inside,and the materials used for the tool have a long life,saving the cost for the long-term use.5.Control effectiveness of releasing Encarsia formosaField biocontrol was carried out by releasing Encarsia formosa.The results showed that after 10 days of releasing Encarsia formosa,significant controlling effectiveness on Bemisia tabaci was reached,and the reduction rate of insect was 50% after 25 days,a rather good control effect.The more the Encarsia formosa,the better the control effectiveness.Therefore,the timely release of Encarsia formosa could be effectively controlled when 3Bemisia tabaci per plant were found in the field.