Oviposition And Feeding Choice Of The Tabacco Whitefly, Bemisia Tabaci (Gennadius) On Different Cucumber Strains

The B biotype Bemisia tabaci is a famous worldwide distributed pest to a great variety of vegetables and ornamental crops. For its short life history, high fecundity and easy acquisition of pesticide-resistance ability, selecting pest-resistant plant strains turns out to be one of the efficient ways to control B. tabaci. We conducted a series of studies on the selection mechanisms for different cucumber strains in the tabacco whitefly in this thesis. Our main results and conclusions are as follows:1. The selection tests on 10 domestic or overseas cucumber strains demonstrated that the tobacco whitefly showed different feeding and egg-laying behaviors to different cucumber strains. Zhongnong 19, 22-35RZ, and Deltastar are the most favorite strains for B. tabaci. The quantity of adults and their eggs on 22-94RZ, Chunguang No.2, and Sijiqiugua strains, however, were the lowest.2. We planted 8 cucumber strains above and 8 other cucumber strains from Holland in the greenhouse, and made an observation on spatio-temporal dynamics of B. tabaci on these plants. Our results showed that the population density varied with different strains, height and time, and there were significant differences among them. The density of populations hosted on Zhongnong No.19 and Deltastar was the highest, and it turned out to be the lowest on Chunguang No.2 strain and 22-94RZ strain. The same results were also obtained from the greenhouse experiment. In addition, we found that there had an outbreak period of the pest during the latter growing time of the cucumber. The pest population density in the top part was significant higher than that in the bottom part of the cucumber, and it was higher on the back than that on the face of the cucumber leaves.3. We investigated the development period and the fecundity of B. tabaci on 5 cucumber strains above in the incubators with 26±0.5°C and 40-60% relative humidity, and we then constructed the life table of the tabacco whitefly. Our results showed that the tabacco whitefly had high fecundity and lived well on any cucumber strains. However, it devoloped faster on Deltastar strain, but slower on Chunguang No.2 strain, and it had the lowest fecundity on 22-94RZ strain.4. The behavior reaction to different cucumber volatiles, the density of leaf trichomes, and the effect of leaf color on the pest population were also investigated in this thesis. We found that therewere no different reactions of the tabacco whitefly to different cucumber volatiles, but it showed a strong behavioral tendency to the kelly leaves. There had significant differences of the leaf trichome density among different cucumber strains, and there had a significant correlation between the leaf trichome density and the quantity of adults and their eggs.5. The contents of soluble sugar in the leaves were significantly different among different cucumber strains, and the ability of pest resistance increased with the higher contents of soluble sugar. In addition, the contents of proteins and amino acids varied with different cucumber strains, and the strains with higher contents of these two components could suffer more pest attacks.