Population Dynamics Of Bemisia Tabaci In Tobacco Fields Of Shandong Province And Control Methods For This Pest

Bemisia tabaci is one of the important insect pests of tobacco. It has caused serious damages inShandong tobacco areas in recent years. In order to elucidate the dynamics and effective control of B.tabaci in the tobacco field, outbreak and severity of this pest were investigated in this study throughfield investigations and laboratory analyses. Furthermore, the resistance of85Tobacco Germplasms toB. tabaci and the preliminary resistance mechanism were evaluated. Effectiveness of different kinds ofpesticides on B. tabaci were also tested. The main results are summarized as follows.1. Occurence degree of Bemisia tabaciThe dynamics of B. tabaci were studied using the systematic investigation, and the maintobacco-producing areas were surveyed in Shandong province. The dynamics of B. tabaci adults in thisprovince were reported to be substantially the same throughout the year, and there was a graduallyincreasing trend between June and July in2011-2013. From the end of May to the early June every year,B. tabaci adults began to appear in fields. With the growth and development of tobacco plants, climaticconditions were more favorable for the occurrence of B. tabaci, thereby the number of adults graduallyincreased, reaching the peak in late July, which was still severe in August. Affected by climate, theoccurrence of B. tabaci showed a certain variation in a year.Investigation on the occurrence of B. tabaci in main tobacco-producing areas in Linyi citydemonstrated that B. tabaci caused damages in each area and the degree of damages varied among areas.The outbreak degree of B. tabaci in cities and counties was in this order: Cangshan> Feixian County>Pingyi> Yinan> Yishui.2. The relationship between occurence degree of Bemisia tabaci and environmental conditionsThe influence of tobacco planting system, terrain, and the distance between tobacco andvegetable-shed on the outbreak degree of B. tabaci was investigated. The results showed that theoutbreak degree of B. tabaci in potato-intercropping tobacco fields was much heavier than that in thetobacco fields. The outbreak degree of B. tabaci in plain tobacco fields was higher than that inmountain tobacco fields, and the outbreak degree of B. tabaci in tobacco fields near the sheds andTrialeurodes vapotariorum in greenhouse was generally heavier.3. Resistance evaluation of tobacco germplasm to Bemisia tabaci and the mechanism of resistanceBemisia tabaci had certain selectivity to different tobacco varieties. In four tobacco varieties:Zhongyan100, G28, NC82and NC89, the selection order for egg laying of B. tabaci adults was:Zhongyan100>G28>NC82and NC89. Zhongyan100was the most favorable for the growth andreproduction of B. tabaci.The resistance of a total of85tobacco varieties (lines) to B. tabaci was investigated. The resistancewas divided into five levels: high resistance level, resistance level, middle resistance level, sense level and high sense level. The standard of resistance degree was developed using an insect quantity ratiomethod.4. Effect of various pesticides on B. tabaciField effects of six kinds of pesticides in controlling B. tabaci were evaluated. The resultsindicated that Acetamiprid and Thiamethoxam had the best effects on prevention and control of B.tabaci in six kinds of agents, showing readily availability and effective duration time of more than7d.The effects of Abamectin and Imidacloprid were intermediate, while the effects of Buprofezin as aninsect growth regulator were slow. On the other hand, the controlling effects of Cyhalothrin were foundto be normal.