title: Pesticide-mediated interspecific competition between local and invasive thrips pests.
abstract: Competitive interactions between species can be mitigated or even reversed in the presence of anthropogenic influences. The thrips species Frankliniella occidentalis and Thrips tabaci are highly invasive and damaging agricultural pests throughout the world. Where the species co-occur, one species tends to eventually predominate over the other. Avermectin and beta-cypermethrin are commonly used insecticides to manage thrips in China, and laboratory bioassays demonstrated that F. occidentalis is significantly less susceptible than T. tabaci to these insecticides. In laboratory cage trials in which both species were exposed to insecticide treated cabbage plants, F. occidentalis became the predominant species. In contrast, T. tabaci completely displaced F. occidentalis on plants that were not treated with insecticides. In field trials, the species co-existed on cabbage before insecticide treatments began, but with T. tabaci being the predominant species. Following application of avermectin or beta-cypermethrin, F. occidentalis became the predominant species, while in plots not treated with insecticides, T. tabaci remained the predominant species. These results indicate that T. tabaci is an intrinsically superior competitor to F. occidentalis, but its competitive advantage can be counteracted through differential susceptibilities of the species to insecticides. These results further demonstrate the importance of external factors, such as insecticide applications, in mediating the outcome of interspecific interactions and produce rapid unanticipated shifts in the demographics of pest complexes.
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Xueyin
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Malheur County Extension, Department of Crop and Soil Science, Oregon State University, 710 SW 5th Ave, Ontario, OR 97914, USA.
authors.forename: Stuart R
authors.initials: SR
authors.lastname: Reitz
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Huiguo
authors.initials: H
authors.lastname: Yuan
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Zhongren
authors.initials: Z
authors.lastname: Lei
authors.affiliation: CSIRO, Black Mountain Laboratories, Acton, ACT 2601, Australia.
authors.forename: Dean Ronald
authors.initials: DR
authors.lastname: Paini
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Gao
mesh_terms: D000818:Animals; D001681:Biological Assay; D003163:Competitive Behavior / Q000187:drug effects*; D005260:Female; D058865:Introduced Species; D007559:Ivermectin / Q000031:analogs & derivatives / Q000633:toxicity; D010575:Pesticides / Q000633:toxicity*; D018515:Plant Leaves / Q000187:drug effects; D011722:Pyrethrins / Q000633:toxicity; D013045:Species Specificity; D061149:Thysanoptera / Q000502:physiology*
chemical_list: D010575:Pesticides; D011722:Pyrethrins; C017160:cypermethrin; D007559:Ivermectin; C019264:avermectin