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GS Analysis On Population Spatio-temporal Dynamics Of Alien Pest Bemisia Tabaci (Gennadius) Invading Cotton Field In Tupan

Posted on:2008-02-18Degree:MasterType:Thesis
Country:ChinaCandidate:N Y MaFull Text:PDF
GTID:2143360215968419Subject:Plant Pathology
Abstract/Summary:PDF Full Text Request
Bemisia tabaci (Gennadius), an alien pest in Xinjiang transported from late of last century, has showed out a great possible threaten to the cotton production. In discussing of the occurrence regularity and the control tactic, Geographic Information System (GIS) technology and geostatistics (GS) methods were initially used to analyze the spatial structure and simulate the spatial distribution of Bemisia tabaci (Gennadius) at cotton field in Xinjiang Tupan region,key results are as the following:1.The monitor of CC-Trap indicated that the green houses are the main locations in harboring Bemisia tabaci (Gennadius) to over winter and it is also the main resources of whiteflies in next year.2. B. tabaci (Gennadius) invade the cotton field from the winter harbor initially transported by downwind,thereafter the distribution was largely affected by the direction of wind. It is a classical insect distributed in virtue of the wind power.3. Based on the analysis of Geographic Information System (GIS) technology and geostatistics (GS) methods, it was observed that the spatial distribution patterns of Bemisia tabaci (Gennadius) on cotton were aggregated, and the aggregation degree was fluctuant along with time and the proportion of the spatial variation randomized extent. The variation in distribution areas and the diffusion trend of adults were monitored by the analysis of GS. Results suggested that the adults of B. tabaci (Gennadius) were correlated spatially in cotton field, Random degree ranged from 19.22% to 49.99%; the distance range of spatial dependence varied from 32 to 6372m in July, then it fluctuated within the distance of 2000~3000m.4. The vertical distribution of B. tabaci (Gennadius) on cotton plant was influenced strongly by the characteristic of warm temperate zone with continental arid desert climate in Turpan. It started to damage the top leaves when distributed by the downwind, whereas to damage leaves in the middle and bottom part of cotton plants when distributed against the wind. The adult quantity in bottom is bigger than that of in the top after the population being established, it is the adaptability of B. tabaci (Gennadius) to the characteristic climate of Turpan region.5. The developmental duration of B. tabaci from egg to adult on cucumber was days of 21.1, while on cotton was days of 18.4.Thus it was deduced that the generations of B. tabaci in Turpan region were probably 15 to 17 in the whole year.6. The surviving rate of B. tabaci from egg to adult on cucumber in green house was 63.67%, while on cotton in feild was 33.48%; The fecundity on cucumber was 187.41 eggs per female, and on cotton was 92.23 eggs per female. It shows that the conditions in green house hosted on cucumber are more suitable for the development of B. tabaci than that of in field hosted on cotton plant. The high mortalities in egg stage and young nymph stage are the key factors in affecting the reproduction of B. tabaci under the two different conditions.7. Two years investigation indicated that B. tabaci couldn't survive from winter in outside naturally. From the beginning of September, it started to fly back to the nearby greenhouse over winter, thereafter invading field by wind in the beginning of next June along with the opening of green house, and started to damage melon as well as some of weeds, subsequently to damage cotton after the harvest of melon in the end of June. It was until the September that B. tabaci flew back to green house again to finish the whole year's life cycle.
Keywords/Search Tags:Bemisia tabaci, geostatistics, population spatial dynamic, ecological characteristics
PDF Full Text Request
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