关键词: 小菜蛾, 寄主干扰, 寄主选择, 种群趋势增长指数, 单作, 混作

Abstract: 【Aim】 Herbivorous insects may have difficulty in decision-making relative to selection of hosts for food and oviposition sites in the presence of multiple suitable hosts. Such potential interference with host selection may affect population dynamics. The objective of this study was to test the hypothesis that mixed populations of similar hosts would suppress population densities of the diamondback moth (DBM), Plutella xylostella (L.). 【Methods】 A randomized complete block (RCB) experimental design with 3 treatments was established in a field naturally infested with DBM. Treatments included mixed cultivation of Brassica campestris L. and B. juncea Coss, both of which are favorable hosts for DBM, and monocultures of either host. Moreover, mixed cultivation with different ratios of B. campestris to B. juncea and different intervals between the two hosts were established in the field also naturally infested with DBM. 【Results】 The population densities of DBM in mixed cultivation were significantly lower than densities on monocultures of either host (F_2,7=14.409 and 6.400 in 2010 and 2012, respectively, P<0.05). A population life table in 2012 yielded the population trend indexes (I) for DBM on B. campestris (I = 6.549) or B. juncea (I = 6.858) that were greater than the values on mixtures of the two hosts (I = 4.797). With B. campestris density increasing, the population densities of DBM first decreased and then increased. No differences were observed among population densities on hosts in mixtures at different intervals within 2 m (F_3,8 = 0.204, P > 0.05). 【Conclusion】 Population densities of DBM are lower on mixtures of favorable hosts, which is consistent with the hypothesis that in such situations the ability of insects to select a host is diminished. This phenomenon may have application value for management of DBM.

Key words: Plutella xylostella, host interference, host selection, population trend index, monoculture, mixed cultivation