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.

Population Numbers and Physiological Response of an Invasive and Native Thrip Species Following Repeated Exposure to Imidacloprid

“…Research also found Thrips tabaci was the dominant species on Brassica oleracea when no insecticide was used but was displaced by F. occidentalis under avermectin and betacypermethrin use (Zhao et al, 2017). Thus, insecticides could be an important factor in intensifying the competition between F. occidentalis and T. tabaci in eastern China (Zhao et al, 2017). In our study, we found that F. occidentalis maintained a higher population density than F. intonsa in three of the sampled host plants in most cases, especially in imidacloprid-used fields.…”

“…For instance, F. occidentalis has displaced F. gemina in Argentina on Lycopersicon esculentum (De Piìccolo et al, 2006), and Thrips hawaiiensis has been displaced by F. occidentalis on Rosa chinensis and Gardenia jasminoides, Cao et al (2018). Research also found Thrips tabaci was the dominant species on Brassica oleracea when no insecticide was used but was displaced by F. occidentalis under avermectin and betacypermethrin use (Zhao et al, 2017). Thus, insecticides could be an important factor in intensifying the competition between F. occidentalis and T. tabaci in eastern China (Zhao et al, 2017).…”

Relative susceptibility to pesticides and environmental conditions of Frankliniella intonsa and F. occidentalis (Thysanoptera: Thripidae), an underlying reason for their asymmetrical occurrence

“…Interspecific competition can be affected by anthropogenic factors such as global warming and farming practice [ 10 , 15 ]. Species displacement by the outcome of interspecific competition, has particular relevance to pest management and conservation biology [ 26 , 27 ].…”

Interference and Exploitation Competition between Frankliniella occidentalis and F. intonsa (Thysanoptera: Thripidae) in Laboratory Assays

“…Increasing densities of F. occidentalis lowered the average reproductive success of F. bispinosa females, which may have caused F. occidentalis to be the better competitor (Northfield et al 2011). Nevertheless, competition can be affected by other external factors, such as weather condition and insecticide application, and pesticide-mediated interspecific competition has recently been reported between local and invasive thrips species in China (Zhao et al 2017).…”