Studies On The Immigration, Diffusion And Distribution Of Bemisia Tabaci On GreenhouseTomatoes In Taizhou

In the past few years, the B and Q biotypes (cryptic species Middle East-Asia Minor 1 and Mediterranean, respectively) of the whitefly Bemisia tabaci have invaded Zhejiang province, China. Simultaneously, begomoviruses that are transmitted by B. tabaci caused serious losses to greenhouse tomatoes. In order to further understand the dynamics of the whitefly’s occurrence and provide information for the control of whiteflies and their transmitted viral disease, this study investigated the damages of whiteflies at the seeding stage of greenhouse tomatoes, the diffusion of whiteflies from the sweet potato to the tomato in two multi-span greenhouses, and the occurrence of whiteflies in single-span greenhouses as well.Our results indicated that tomato plants were damaged by whiteflies since the plants were at the seeding stage. Whiteflies began to diffuse from the sweet potato to tomato 13 days after the transplantation of tomato plants. It took at least 3 days for whiteflies to complete the diffusion between adjacent ridges. The occurrence of eggs and nymphs of whiteflies in the edge ridge and middle ridge gradually converge in multi-span greenhouses. By contrast, the occurrence of the eggs and early-stage nymphs on the upper and middle parts of the plants in the middle ridge was more serious than that in the edge ridge in single-span greenhouses.The seeding stage of tomato is the most sensitive to the introduction of whitefly-transmitted begomoviruses, so it is necessary to use insect nets for isolated breeding. Since the diffusion of whiteflies from sweet potato to tomato is relatively slow, so it is not necessary to choose tomato lands far away from sweet potato lands in the autumn and winter. Considering the adults, eggs and early-stage nymph of whiteflies mainly occurred in the upper and middle part of the plants, we’d better spay insecticides onto the upper and middle part of plants instead of the whole plant when the chemical control is used. Because a large number of third instar nymphs and fourth instar nymphs occurred in the lower part of plants, it is recommended to clean the old leaves of lower part of plants. Finally, the difference of whitefly damages in single- and multi-span greenhouses needs further investigation.