Epidemiology And Integrated Control Of Tomato Yellow Leaf Curl Virus Disease In Wenzhou

Geminiviruses are plant viruses characterized by their unique twinned particles, which encapsidate a circular single-stranded DNA genome. Under natural conditions, all of them are spreaded by the whitefly (Bemisia tabaci), and they are called whitefly-tansmitted geminiviruses (WTG). With serious invasion of the whitefly (B whitefly) in recent years, an epidemic outbreak of Tomato yellow leaf curl virus (TYLCV) disease in greenhouses took place in Wenzhou areas over 350 ha in 2006, which caused an economic loss of over 10 million yuan (RMB). As a brand-new disease for domestic emergence, it is urgently needed to following technical issures be figured out for agricultural production:(1) diagnostic techniques on Whitefly-transmitted geminiviruses; (2) understanding on prevalent regularity of the disease with effective monitoring; (3) preventive and controlling guidance on production by comprehensive techniques.This study was supported by Major Fundings of Agricultural Science and Technology in both Wenzhou and Zhejiang (No.2007C12054 and N20070021, respectively). Molecular identification of virus polymerase chain reaction (PCR), lab experiments on transmission of viruses, investigation in fields, and demonstrative expansion on controlling effects in fields. were all studied in the past three years. The results showed that:(1) the plant disease pathogen is Tomato leaf curl Taiwan virus (ToLCTWV) in Wenzhou, and a set of diagnostic techniques through symptoms and molecular identification were established, (2) the cycling rules of invasion and infection of ToLCTWV is comprehensible, which figured out that appropriate delay in the host seedtime may helpful for alleviate damage. (3) the spreading ability of ToLCTWV by B. tabaci (B whitefly) was clarified, and. influences on efficiency of virus transmission were clear on whitefly population density, host seedling age. and temperature. (4) population dynamics of B. tabaci in Wenzhou were monitored, as control index was set up during seedling age, with establishment of model on population forecast. (5) integrated control, such as seedbed cleaning (eradicating the intermediate host plants), isolation by insect-proof masks, yellow board traps, and spraying low-toxic pesticide during seedling, were all used against viruses effectively. The controlling effect appeared to be over 95%.In the last three years, the proposed integrated control technology was extensively used in Wenzhou. The total area of farms using this technology was about 5400 ha, reducing the usage of pesticide about 2-3 times quarterly, and reducing the pesticide dose by 40%. The control costs were saved about 4.9 million yuan. Besides, the loss of tomato yield was reduced by 7.8300 tons, increasing earnings of 145 million yuan. The results indicated that the social, economic and ecological benefits of the technology were significant.