| Ophraella communa (Coleoptera:Chrysomelidae) of North American origin is a recently discovered exotic herbivorous insect in China mainland. It has been known that its host plants are limited to a few closely related plants in Heliantheae, Compositae, among which Ambrosia artemisiifolia is its dominant host plant in the field. It also occasionally attacks Xanthium canadense. In order to predict its potential risks to plants other than the target weed A.artemisiifolia, we conducted a series of experiments to investigate oviposition choice for plants as affectd by plant species (cultivars), learning, and plant traits.1.Ovipositon choice among target and non-target plants of O. communaThe recognition time concept was introduced, and survival analysis regression model fitted to recognition time until plants were oviposited, so as to evaluate oviposition risks of target weed A.artemisiifolia and testing nontarget plants. The non-target plants tested included A.trifida,X. sibiricum,two varieties of Helianthus annuus,H. multiflorus,and H. tuberosu in tribe Heliantheae of Composite. The results showed that A. trifida and X. sibiricum were equally susceptible to oviposition compared to the target weed. The common sunflower H. annuus was equally susceptible to the first feeding of neonate larvae as the target weed A. artemisiifolia. Finally, the potential risk of O. communa to non-target plants in areas where it is used as a biological control agent of the alien invasive weed A. artemisiifolia is discussed.2.Effects of experiences on oviposition choice of O. communaPrevious foraging behavior of phytophagous insects on host plants may have influences on successive selection behavior. Previous experiences of feeding, overwintering, and larval development were observed on later oviposition choice among testing plants. The results showed that (ⅰ) adult O. communa with experience of feeding on A. artemisiifolia after emergence preferred A. artemisiifolia to the other plants for laying eggs, and the number of eggs laid was as many in A. artemisiifolia as in A. trifida but more than in the other plants;(ⅱ) adult O. communa with experience of feeding on X. sibiricum after adult emergence exhibited same tendency for laying eggs in A. artemisiifolia as in X. sibiricum, but higher liability of egg-laying in A.artemisiifolia than other testing plants;(ⅲ) adult O. communa with experience of overwintering on X. sibiricum behaved similarly compared to that with experience of feeding the plant; (ⅳ) adult O. communa with experience of development at larval stage on X.sibiricum, preferred A. artemisiifolia to the other testing plants for laying eggs.3.Effects of plant traits on oviposition choice of O. communa on A. artemisiifoliaPlant traits, including plant height, levels of damage made by larvae, and eggs laid in A. artemisiifolia, were observed as affecting ovipositon choice of O. communa.Two variables, selection ratio and recognition time, were analysed. The results showed that (i) there was no significant differences in oviposition selection among plants with heights of 20cm,40cm,60cm; (ⅱ) there was a significant difference in selection frequency among three different larval damage levels, but no differences in the recognition time, (ⅲ) Adults showed no significant difference from A.artemisiifolia with different numbers of egg patches (0,4 and 8 patches)4. Oviposition selection of O. communa in the fieldTo gain insight into oviposition selection on A. artemisiifolia with different traits, a survey was made for egg-laying time on A. artemisiifolia with different characteristics in Nanjing,and the variable recognition time was fitted with Cox proportional hazard model to examine effects of covariates.The results showed that plant damage level, patch size, and shading significanltly influenced risk of being oviposited on A.artemisiifolia. |
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