Effects Of Elevated CO₂ On The System Of Tomato, Bemisia Tabaci Biotype B And Encarsia Formosa

Global change, especially the rise of CO₂ concentration in atmosphere, has been a focus of great concern for the scientific community. Elvated CO₂, not only affects the plant growth and development, but also changes the chemical contents and composition of plant tissues, which indirectly affects the herbivorous insects, even infuences the food chain of natural enemies. Whitefly (Bemisia tabaci) is an important pest worldwide. Nowadays, it becomes serious and serious in many provinces of China. and has caused a great economic loss. With the development of"Green Agriculture"in our country, biological control agents have played an important role. Encarsia formosa is a significant natural enemy of B. tabaci in green house. In this study, the open-top chambers (OTC) were systematically used to study the effects of elevated CO₂ on the systems of tomato, B. tabaci and E. formosa. The results as follows:1) The tomato growth could be accelerated by elevated CO₂. As the concentraton of CO₂ increased, the height of tomato plant, fresh and dry weight of per plant, above-ground and under-ground biomass and number of trichomes on leaves were significantly higher than those growing under the ambient CO₂ levels. The nutritional components of the tomato leaves were variable with the concentraton of CO₂ changed. Under the elevated CO₂ treatments, the contents of carbon and the ratio of TNCs in tomato leaves wrere significantly higher than those from the check plots, while the contents of nitrogen obviously decreased and without distinct change on the contents of soluble protein and free amino acids .2) The developments and fecundities of 3 successive generations of whitefly, Bemisia tabaci, reared on leaves of tomato grown under elevated CO₂ (double-ambient vs. ambient) in open-top chambers(OTCs) were examined quantitatively. The results showed that the fecundities and average adult longiveties of 3 successive generations of whitefly reared on leaves of tomato grown under elevated CO₂ were not obviously different with those from check plots. The development durations of egg, 2nd and 4th instar nymphae of the first generation were significantly prolonged. The egg survival rate and adult emergence of the F1 generation were distinctly lower than those in check plots. The development durations of egg, 4th instar nymph and tolal duration from egg to adult of the F2 generation were significantly prolonged, while the egg duration, survival rates of 1st instar nymph and adult emergence of the F2 generation were obviously lower than those in check plots. The development durations of egg, 1st-4th instar nymphae and tolal duration from egg to adult of the F3 generation were significantly prolonged, while the egg survival rates and adult emergence of the F3 generation were obviously lower than those in check plots. The result of the host selectivity of B. tabaci reared in both ambient and double-ambient CO₂ atmospheres indicated that the F3 whiteflies were preferred to lay their eggs on the tomato grown in double-ambient CO₂ atmosphere. 3) The observation on the bionomics of Encarsia formosa reared from ambient CO₂ atmosphere and parasitized in whitflies in double-ambient CO₂ atmosphere showed that the most bionomics of E. formosa were not obviously different except for its egg duration and the egg laying time, which were significantly prolonged.4) The observation on the bionomics of Encarsia formosa reared from double-ambient CO₂ atmosphere and parasitized in whitflies in ambient CO₂ atmosphere showed that most bionomics of E. formosa were not obviously different from the parasite reared from double-ambient CO₂ atmosphere.5) The correlation analysis on the amount of egg production per 72h of the whiteflies reared from different CO₂ concentrations with the nutrition of tomato, such as: soluble protein, free amino acids, carbon, nitrogen and the ratio of TNCs etc., only a significant positive correlation with the contents of carbon was shown.