Insecticide-Mediated Apparent Displacement between Two Invasive Species of Leafminer Fly

Abstract

BackgroundClosely related invasive species may often displace one another, but it is often difficult to determine mechanisms because of the historical nature of these events. The leafmining flies Liriomyza sativae and Liriomyza trifolii have become serious invasive agricultural pests throughout the world. Where both species have invaded the same region, one predominates over the other. Although L. sativae invaded Hainan Island of China first, it recently has been displaced by the newly invasive L. trifolii. We hypothesized that differential susceptibilities to insecticides could be causing this demographic shift.Methodology/Principal FindingsAvermectin and cyromazine are the most commonly used insecticides to manage leafminers, with laboratory bioassays demonstrating that L. trifolii is significantly less susceptible to these key insecticides than is L. sativae. In trials where similar numbers of larvae of both species infested plants, which subsequently were treated with the insecticides, the eclosing adults were predominately L. trifolii, yet similar numbers of adults of both species eclosed from control plants. The species composition was then surveyed in two regions where L. trifolii has just begun to invade and both species are still common. In field trials, both species occurred in similar proportions before insecticide treatments began. Following applications of avermectin and cyromazine, almost all eclosing adults were L. trifolii in those treatment plots. In control plots, similar numbers of adults of the two species eclosed, lending further credence to the hypothesis that differential insecticide susceptibilities could be driving the ongoing displacement of L. sativae by L. trifolii.Conclusions/SignificanceOur results show that differential insecticide susceptibility can lead to rapid shifts in the demographics of pest complexes. Thus, successful pest management requires the identification of pest species to understand the outcome of insecticide applications. These results further demonstrate the importance of considering anthropogenic factors in the outcome of interspecific interactions.

Adaptation of acaricide stress facilitates Tetranychus urticae expanding against Tetranychus cinnabarinus in China

“…The causes of the demographic change are not always clear and may be attributed to various biological mechanisms or anthropogenic factors, including differences in their respective reproductive success, and susceptibility to acaricides. Similar effects can be seen in other insect species, where it has been reported that the application of insecticides can lead to rapid shifts in the composition of leafminer complexes in laboratory and field‐based experiments (Gao, Reitz, Wei, Yu, & Lei, 2012). Although the greater resistance of T. urticae versus T. cinnabarinus to acaricides is generally recognized, it is unclear whether acaricides facilitate the expansion of T. urticae , resulting in T. urticae being the dominant species of spider mites.…”

“…Similarly, Gao, Lei, Abe, and Reitz (2011), Gao et al. (2012) suggested that differential susceptibility to commonly used insecticides could account for the replacement of Liriomyza sativae by Liriomyza trifolii on Hainan Island of southern China (Gao et al., 2011, 2012). However, the underpinning mechanisms behind the differential susceptibility to insecticides for these Bemisia spp.…”

“…This difference allows the Q biotype to overcome the competitive advantage that the B biotype has in the absence of insecticide pressures (Elbaz et al, 2012;Pascual & Callejas, 2004). Similarly, Gao, Lei, Abe, and Reitz (2011), Gao et al (2012) suggested that differential susceptibility to commonly used insecticides could account for the replacement of Liriomyza sativae by Liriomyza trifolii on Hainan Island of southern China (Gao et al, 2011(Gao et al, , 2012. However, the underpinning mechanisms behind the differential susceptibility to insecticides for these Bemisia spp.…”

A decade of leafminer invasion in China: lessons learned

“…21,26,28 While no unique, specific mechanisms have been identified as causing the displacement of L. sativae by L. trifolii, field surveys have indicated that insecticide use can produce significant changes in the complex of Liriomyza species in China. 29 L. trifolii populations tend to be more tolerant to commonly used insecticides than L. sativae. Studies indicate that the capacity of L. trifolii populations to develop insecticide resistance has enabled it to replace L. sativae as the primary leafminer in several cropping sytems.…”

“…While no unique, specific mechanisms have been identified as causing the displacement of L. sativae by L. trifolii , field surveys have indicated that insecticide use can produce significant changes in the complex of Liriomyza species in China . L. trifolii populations tend to be more tolerant to commonly used insecticides than L. sativae .…”