Study On Occurrence Regularity And Control Of Bmisia Tabaci (Gennadius) In Cotton Fields In Dunhuang City

The research surveyed the host plant of Bmisia tabaci (Gennadius) and its occurrence in Dunhuang city. The biotype of B. tabaci was identificated. Through systemically survey its occurrence regularity was studied, quantity of B. tabaci on different cotton varieties was investigated and compared, and the control of B. tabaci was also investigated. The results were as follows:1. Based on the experiment of zucchini it was discovered that the treatment group of zucchini was gradually emerged silver leaf reaction in July 11, then all of which were emerged silver leaf reaction in July 15. But the control group of zucchini was not emerged silver leaf reaction. Indoor research also show that most of B. tabaci in Dunhuang city did not have the 4 before sub marginal setae , most of the wax fringes on tail stigmata was narrow than that of caudal setae .This results indicated that the biotype of B. tabaci in cotton fields in Dunhuang city was B.2. Based on the survey of agricultural crop, horticultural crop,flower and weeds at farmland,garden park and public green space in unhuang city in 2006 it was found that there are 38 species of host plant of B. tabaci , which were belong to 14 families, most of which were Solanaceaee, cucurbitaceae and Cruciferae. Based on the survey of damage level of different host plant it found that occurrence of B. tabaci was universally serious, and the damage of Solanaceaee,Leguminosae and cucurbitaceae was most severe. Fitness of B. tabaci to different host plants were quiet different, and the optimum host plant was cucumber pumpkin and cotton.3. B. tabaci can not live through the winter outdoor in Dunhuang city, but it can live through the winter in greenhouse. B. tabaci spread from greenhouse to cotton field in May of the second year. The farther it spread from greenhouse, the less quantity was emitted when it spread. The quantity of B. tabaci that was captured by the yellow boards which has different distance from greenhouse was significantly different. Quantity of B. tabaci captured by yellow board that in cotton field with 10m from greenhouse was 123.12, significantly more than the other four treatments; Quantity of B. tabaci captured by yellow board that in cotton field with 50m from greenhouse was 34.33, significantly less than the other four treatment. B. tabaci generally first occurrence in the cotton field which nearer to greenhouse, quantity of B. tabaci in the cotton field which near to greenhouse was relatively high, the cotton in that field was damaged seriously. Quantity of B. tabaci in cotton field with 10m from greenhouse was significantly higher than that with 50 m.4. The emergence of B. tabaci on cotton fields was in the last ten days of May in Dunhuang city. And then it generally appeared in the last ten days of June, but its population density was at a lower level. It came into being a peak of adults in the first ten days of August,the peak of adults quantity was 1073 pests per100 leaves, then its population density was at a higher level As the temperature decreases and cotton was plucked, B. tabaci decreased gradually in the last twenty days of September. Population dynamics of the eggs and nymphs generally accord with adults.5. Quantity of B. tabaci was different in different cotton varieties. Of which quantity on Dunmian V3 was the least, its average quantity on three leaves of ten plants was 126.69, which is significantly lower than the other four cotton varieties. Quantity on Longmian NO.1 was the most, its average quantity on three leaves of ten plants was 233.33, which was significantly higher than the other four cotton varieties. Quantity of Dunmian69108, Xinluzao NO.13 and Dunmian9916 were in the middle.6. The vertical distribution showed adult quantity B. tabaci that mainly concentrated in the upside of cotton in the widespread occurrence period (July 1 to September 20), and it was significantly higher than that of in middle and lower. Distribution of eggs and nymphs are accord to adults. At the level of distribution, spatial distribution of B. tabaci adults was aggregated distribution, Individuals among the group exclude each other. Spatial distribution of nymphs and eggs was negative binominal distribution, and its component was individual colony. The theoretical sampling model of B. tabaci on cotton was obtained by Iwao method. Adults: n=(t/D)~2[(0.55609/m)+1.87770] Nymphs: n=(t/D)~2[(3.84487/m)+2.58538] Eggs: n=(t/D)~2[(25.53052/m)+3.33355]7. The efficacy to B. tabaci was different among some pesticides. After one day Luojiya and Bifenthrin have the best efficacy, which correct control efficacy was66.17% or68.56%. After three days Thiamethoxam Jieshiaoke and midacloprid have the best efficacy, which correct control efficacy was 88.68% 82.66% or68.19%. The results of variance analysis suggested that control efficacy of Thiamethoxam and Jieshiaoke were significantly better than the other pesticides. All control efficacy were descended after five or seven days, after or seven days Jieshiaoke have the best control efficacy, which was still 70.26%.