Location: Insect Behavior and Biocontrol ResearchTitle: Species displacements are common to two invasive species of leafminer fly in China, Japan and the United States) Author
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2011
Publication Date: 12/1/2011
Citation: Gao, Y., Lei, Z., Abe, Y., Reitz, S.R. 2011. Species displacements are common to two invasive species of leafminer fly in China, Japan and the United States. Journal of Economic Entomology. 104:1771-1773. Interpretive Summary: Invasive leafmining flies in the genus Liriomyza are among the most destructive pests of vegetable and ornamental crops worldwide. In particular, Liriomyza sativae and Liriomyza trifolii have been introduced throughout the world, attacking many of the same crops. However, where the two species have both been introduced, one will often, rapidly displace the other. Scientists with the Chinese Academy of Agricultural Sciences and the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology Gainesville, Florida, conducted long term surveys of the leafminer complex on Hainan Island, China, which is a major vegetable production region. Liriomyza sativae was first introduced in 1993 and was widely distributed in Hainan by the first survey that was conducted in 1999. Liriomyza trifolii was first found on Hainan Island in 2005, and by 2007 both species were prevalent. However, by 2011, Liriomyza trifolii had completely displaced L. sativae. Further experiments to elucidate the mechanisms underlying this displacement showed that L. trifolii populations from Hainan Island were much less susceptible to commonly used insecticides than were populations of L. sativae. These results are similar to the situation reported in California where differential insecticide tolerances are thought to have led to the displacement of L. sativae by L. trifolii. In contrast, Japanese scientists have reported that the greater fecundity of L. sativae has enabled it to outcompete L. trifolii in that country. These results will be useful in understanding the population dynamics of these invasive species and improving management plans for them.
Technical Abstract: Under field conditions, species displacements have occurred in different directions between the same invasive species of leafminers (Diptera: Agromyzidae). Liriomyza sativae (Blanchard) was displaced by L. trifolii (Burgess) in the western USA, with evidence suggesting that lower insecticide susceptibility is a factor. However in Japan, the opposite occurred, as L. trifolii was recently displaced by L. sativae. This displacement is probably due to the higher fecundity of L. sativae and differential effects of parasitoids on the two leafminer species. Here, we carried out long-term surveys of the same two invasive leafminer species during January-March in 1999, 2007 and 2011, as well as June-July in 2011, in eight locations (Sanya, Dongfang, Haikou, Leidong, Lingshui, Wuzhisan, Qionghai, and Danzhou) across Hainan Island of southern China. Our results indicate that, between 2007 and 2011, L. trifolii rapidly replaced L. sativae as the predominant leafminer of vegetables on Hainan Island, similar to the situation in the USA. Further surveys revealed that avermectins and cyromazine are the two most frequently used insecticides against leafminers on Hainan Island. Dose-mortality tests showed that L. trifolii populations from Hainan Island are less susceptible to avermectins and cyromazine compared with L. sativae populations. This lower insecticide susceptibility of L. trifolii may be associated with the displacement of L. sativae by L. trifolii, although additional factors such as other environmental factors cannot be ruled out.