Studies Of Resistance To Thiamethoxam On Alien Invasive Pest: B-biotype Bemisia Tabaci

Bemisia tabaci Gennadius (Homoptera:Aleyrodidae) is one of the mostdevastating agricultural pests. Which damage vegetables, ornamental crops,and other economic crops. There are several biotypes in this species, amongthem B-biotype is the most devastating one and distribute worldwide.Thiamethoxam (Actara?) is a kind of recently introduced neonicotinoidinsecticides which act on insect nicotinic acetylcholine receptors. For differenttarget sites, this kind of insecticides was recognized as an appropriatesubstitute product to conventional insecticides and is being widely used forBemisia tabaci control in field. To the better control of Bemisia tabaci, it is very important to understandthe resistance risk and resistance mechanisms of this insect to thiamethoxam.In the thesis, the adult bioassay method, resistance selection, cross resistance,biochemical mechanism, and resistance fitness of Bemisia tabaci tothiamethoxam were investigated, at the same time the biotype of the targetBemisia tabaci was also identified using molecular technique. The experimental Bemisia tabaci populations collected from Beijinggreenhouse was identified to be B-biotype by the molecular maker ofMitochndrial cytochrome oxidase I (mtDNA COI) sequences with the Isrealand Texas B-biotype populations as controls. A new bioassay method, adultleaf dip method of B-biotype Bemisia tabaci was developed, and thesusceptible baselines of Bemisia tabaci to14 insecticides were achieved usingthis method. A 26.98 fold Thiamethoxam– resistant strain of Bemisia tabaci wasachieved after 14 successive selection in 23 generations under the pressure ofkilling about 30~70% population. This resistant strain showed some toleranceto imidacloprid and acetamiprid, and negative cross-resistance to abamectin.PBO and TPP did not synergize thiamethoxam in susceptible strain, but with asynergism ratios of 12.23 and 9.47 in the resistant strain, respectively.Theactivities of CarE , MFO and AchE in the selected strain and another field 3外来入侵生物-B 型烟粉虱对噻虫嗪抗药性研究resistant strain were higher than that in susceptible strain. At the same time theKM value and Vm of AchE in the resistant strain also differed from that insusceptible strain. However there was no significant difference among threestrain in GST activities and esterase PAGE banding.Biological fitness was compared among three strains. The resistant strainshad longer development time from egg to adult, 10 days shorter lifetime and40% less oviposition for female adult.