**1. Introduction**

Leafmining flies in the genus *Liriomyza* (Diptera: Agromyzidae) are among the most eco‐ nomically important pests of vegetable and floriculture crops worldwide. Of the more than 300 species in the genus, approximately 24 species are economically important (Spencer, 1973). Among these, three species are of particular importance as crop pests. *Liriomyza huidobrensis* (Blanchard), *Liriomyza sativae* Blanchard, and *Liriomyza trifolii* (Bur‐ gess) are highly invasive species that have become established in agricultural areas throughout the world. These three highly polyphagous species cause extensive damage to a wide range of high value vegetable and floriculture crops. Other locally important members of the genus include *L. langei* Frick, which is a pest of ornamental and vegeta‐ ble crops in coastal areas of California, USA (Parrella, 1982; Reitz et al., 1999); *L. bryoniae* (Kaltenbach), which is primarily a pest of glasshouse tomatoes in Europe (Smith, 1999), and of glasshouse and field crops in east Asia (Abe & Kawahara, 2001); and *L. chinensis* (Kato) which is a pest of *Allium* crops throughout Asia (Andersen et al., 2008; Chen et al., 2003; Spencer, 1990). Because these and other regionally important pest species share many of the same biological attributes and pest management challenges of the major in‐ vasive pest species, they too may become invasive pests of concern in the future. The following discussion of lessons learned from the three predominant pest *Liriomyza* spe‐ cies will help to provide information to minimize the threat of problems arising from other species and to avoid past mistakes. Ultimately, successful management of any of these species depends upon on development of comprehensive integrated pest manage‐ ment (IPM) strategies that address management of all pests in a cropping system.

Crop plants are damaged by *Liriomyza* by two means. The first form of damage is caused as females use their ovipositor to puncture the leaf surface to lay eggs and to create feeding

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holes (Bethke & Parrella, 1985). The stippling patterns left from these punctures degrade the aesthetic value of ornamental plants, and sufficiently high levels of this puncture damage can reduce plant photosynthesis (Trumble et al., 1985). In addition, young seedling plants can be killed by intense puncture damage (Elmore & Ranney, 1954). Nevertheless, damage from female feeding and oviposition is generally minor in comparison with the more pro‐ nounced mining activity of larvae as they feed within leaves and stems of plants. Larval feeding not only reduces the marketability of plants because of the aesthetic damage, but it also reduces the photosynthetic capacity of plants, which reduces plant vigor, growth and yield (Al-Khateeb & Al-Jabr, 2006; Trumble et al., 1985). Sufficiently high densities of larvae can lead to defoliation. Leafminer caused defoliation can lead to significant losses in fruiting crops because the fruit becomes exposed to sunscald damage from the loss of the plant cano‐ py (Schuster & Everett, 1983). On a per capita basis, *Liriomyza huidobrensis* has the most sig‐ nificant effect on host plants because it creates large mines in the spongy mesophyll of foliage and in petioles (Parrella et al., 1985). It is also known to mine pods of pea plants (*Pisum sativum* L.) (CABI, 2004). In contrast, *L. trifolii* and *L. sativae* tend to mine only through the upper palisade mesophyll of foliage.

present in California, USA since the early 20th century, but it is uncertain if the species that Oatman and Michelbarger termed *Liriomyza pictella* (Thomson) in a series of seminal biological studies (Oatman, 1959; 1960; Oatman & Michelbacher, 1958; 1959) was *L. pictel‐*

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The endemic range of *L. trifolii* is thought to encompass eastern North America, the Carib‐ bean Basin, and parts of South America, although this range must be interpreted cautiously, again because of historical taxonomic uncertainty (Scheffer & Lewis, 2006; Spencer, 1965; 1973). Spencer (1965) noted that *L. trifolii* was widespread throughout Florida but did not consider it to be as significant of a pest as *L. sativae* at that time*.* The *L. trifolii* discussed by Frick (1959) as occurring in the western USA (California, Oregon, Washington) was later de‐

*Liriomyza huidobrensis* was first described, as *Agromyza huidobrensis,* from specimens reared from *Cineraria* in Argentina (Blanchard, 1926). For many years, *L. huidobrensis* was considered to be endemic to North America and to South America, although it was not recorded from Central America (Parrella, 1982; Spencer, 1973). In North America, this species was considered to be present in the far western states of the United States (Cali‐ fornia, Hawaii, Oregon, and Washington) (Spencer, 1973), but recent molecular research has confirmed that this North America taxon is a distinct species, *Liriomyza langei* Frick

Adding to the taxonomic complexity regarding *Liriomyza* is the recent discovery that *L. sati‐ vae* and *L. trifolii* are each composed of biologically distinct cryptic species (Scheffer & Lewis, 2005; 2006). There is evidence that other pest *Liriomyza* species may also be composed of bio‐ logically distinct cryptic species (Lonsdale, 2011; Morgan et al., 2000; Reitz & Trumble, 2002b). Genetic and ecological differences among such cryptic species have important impli‐ cations for understanding the pest status and management of these species (Rosen, 1978;

In addition to our evolving understanding of the taxonomy of *Liriomyza,* the history of *Liriomyza* spp. as pests has changed substantially over time. Although leafminers have been recognized as pests for many years, they remained relatively minor pests in limited geographic areas through the early 20th century (Hills & Taylor, 1951). In Florida, prob‐ lems with leafminer control began to appear in the 1940s, which coincides with the ad‐ vent of the use of synthetic insecticides (Hayslip, 1961; Wene, 1953). The initial species to cause these problems was *L. sativae* (Spencer, 1973). From the 1940s through the 1970s, there were repeated failures of insecticides to control leafminers in Florida (Hayslip, 1961; Levins et al., 1975; Wolfenbarger, 1954) and in the Rio Grande Valley of Texas (Wene, 1953), leading to substantial crop damage periodically. By the late 1970s, *L. trifolii* had become the predominant leafminer pest in Florida, and it soon became the most im‐ portant pest of tomato (*Solanum lycopersicum* L.) in the state (Waddill et al., 1986). This sudden explosion of leafminer problems led growers to intensify insecticide treatments in attempts to manage the problems. Waddill et al. (1986) note that soon after the out‐ break of *L. trifolii* growers were making three or more insecticide applications per week

against leafminers with little success in managing the problem.

*la*, *L. sativae* or another undescribed sibling species.

termined to be a new species, *L. fricki* Spencer (1965).

(Scheffer, 2000; Scheffer & Lewis, 2001).

Scheffer & Lewis, 2005).

In addition to the direct damage inflicted to crop plants, producers may suffer further eco‐ nomic losses because of quarantine restrictions that constrain international trade (Gitonga et al., 2010). Producers lose export markets when importing countries ban products because of the actual or potential presence of leafminer infestations in the country of origin. Even with‐ out complete bans, phytosanitary measures (e.g., fumigation or irradiation (Hallman et al., 2011)) required by importing countries may make exports cost prohibitive for producers in the country of origin.
