Abstract: We used five-point sampling and sticky board method to investigate population dynamics of F. occidentalis on chrysanthemum seedlings under different planting environments. The effects of F. occidentalis size of fore-rotating seedlings on F. occidentalis size of current-rotating seedlings were analyzed from 2018 to 2020. The results showed that population size of F. occidentalis increased first and then decreased in both the fore-rotating and current-rotating seedlings. The duration of the main activity period of F. occidentalis was related to the planting time of chrysanthemum seedlings. The main activity period of F. occidentalis on fore-rotating seedlings were from late March to late June under different planting environments, with peak population size of 654.6 ind·board^-1 in open field, 373.8 ind·board^-1 in single greenhouse and 146.4 ind·board^-1 in conjoined greenhouse. The main activity period of F. occidentalis on current-rotating seedlings was from mid-July to mid-October, while population peaked to 551.2 ind·board^-1 in single greenhouse, 134.3 ind·board^-1 in open field and 57.7 ind·board^-1 in conjoined greenhouse. F. occidentalis population size on fore-rotating seedlings during the main activity period was in an order of open field > single greenhouse > conjoined greenhouse, while that on current-rotating seedlings was in an order of single greenhouse > open field > conjoined greenhouse. The effect of F. occidentalis population size of fore-rotating seedlings on F. occidentalis population size of current-rotating seedlings was increased in an order of open field > single greenhouse > conjoined greenhouse. The population size of F. occidentalis of fore-rotating seedlings in conjoined greenhouse had the lowest influence on that of current-rotating seedlings, which could effectively control the population size of F. occidentalis on the chrysanthemum seedlings.

Key words: Frankliniella occidentalis, population size, population dynamics, fore-rotating seedling, current-rotating seedling.