Abstract: We examined the dynamics of Bemisia tabaci and its dominant natural enemies in tomato fields from three major types of agroecosystems in Kunming, Yunnan Province, including flower, river, and mountain. Five-point sampling method was used to systematically quantify the numbers of B. tabaci and its natural enemies. The population dynamics of B. tabaci were analyzed by quartile method. The niche correlation index was used to analyze the relationship between B. tabaci and its dominant natural enemies in temporal niche. The results showed that tomato field in flower agroecosystem held the lowest densities of nymphs and adults B. tabaci during main activity period, which were 44.66 and 36.25 individuals per plant, respectively. The nymphs and adults B. tabaci in tomato field of river agroecosystem had the highest densities, which were 645.79 and 449.04 individuals per plant, respectively. Tomato field in flower agroecosystem had the maximum natural enemy species, including Nesidiocoris tenuis, Menochilus sexmaculatus, Harmonia axyridis, Encarsia formosa and Eretmocerus hayati. The population densities of N. tenuis, M. sexmaculatus, H. axyridis and E. formosa in tomato field of flower agroecosystem were 1.90, 1.66, 1.79, 2.19 fold to river agroecosystem, and 1.61, 1.16, 1.24, 1.43 fold to mountain agroecosystem during in main activity period, respectively. M. sexmaculatus had the largest temporal niche overlap with B. tabaci in tomato field of the three agroecosystems. Moreover, M. sexmaculatus had the closest spatial-following relationship with B. tabaci, with the gray correlation degrees with B. tabaci in flower, river and mountain agroecosystems being 0.32, 0.38 and 0.35, respectively. The largest temporal niche overlap index of dominant natural enemies and B tabaci presented in flower fields of agroecosystem tomato, indicating that increasing the proportion of flowering plants around cropland can increase the diversity of natural enemies and thus inhibit the outbreak of B. tabaci population.

Key words: Bemisia tabaci, agroecosystem, natural enemy, population dynamics, temporal niche.