''Liriomyza trifolii'', known generally as the American serpentine leafminer or celery leafminer, is a species of
leaf miner fly in the family
Agromyzidae
The Agromyzidae are a family commonly referred to as the leaf-miner flies, for the feeding habits of their larvae, most of which are leaf miners on various plants.
A worldwide family of roughly 2,500 species, they are small, some with wing l ...
.
''L. trifolii'' is a damaging pest, as it consumes and destroys
produce
Produce is a generalized term for many farm-produced crops, including fruits and vegetables ( grains, oats, etc. are also sometimes considered ''produce''). More specifically, the term ''produce'' often implies that the products are fres ...
and other plant products. It commonly infests
greenhouse
A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of transparent material, such as glass, in which plants requiring regulated climatic conditions are grown.These ...
s and is one of the three most-damaging
leaf miner
A leaf miner is any one of numerous species of insects in which the larval stage lives in, and eats, the leaf tissue of plants. The vast majority of leaf-mining insects are moths ( Lepidoptera), sawflies ( Symphyta, the mother clade of wasp ...
s in existence today. It is found in several countries around the globe as an
invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...
, but is native to the
Caribbean
The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
and the
Southeastern United States
The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern por ...
.
Description
''L. trifolii'' are relatively small flies for their family. The adults typically measure less than 2 mm in length. They are mostly yellow in color, although parts of the abdomen and thorax are dark brown or grey. They typically have yellow legs. A key distinction between ''L. trifolii'' and their very similar relatives, '' L. sativae,'' are ''L. trifolii's'' dark, matte mesonotum
The mesothorax is the middle of the three segments of the thorax of hexapods, and bears the second pair of legs. Its principal sclerites (exoskeletal plates) are the mesonotum (dorsal), the mesosternum (ventral), and the mesopleuron (lateral) on ...
.
''L. trifolii'' typically have a wingspan
The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the other wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingspan of ...
of 1.25 to 1.90 mm. Their wings are transparent and have veins in a similar pattern to that of flies in the Phytomyzinae
Phytomyzinae is a subfamily of flies in the family Agromyzidae. There are at least 520 described species in Phytomyzinae.
Genera
* '' Amauromyza''
* '' Aulagromyza''
* ''Calycomyza''
* '' Cerodontha''
* ''Chromatomyia''
* '' Haplomyza''
* ''Lir ...
subfamily.
Distribution
Originally, ''L. trifolii'' was solely found in Caribbean
The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
countries and the southeastern United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
(specifically concentrated in southern Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
). However, export of produce and other vegetative goods from these areas has led to the dispersion of ''L. trifolii'' to several countries in Asia
Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
along the Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
, as well as Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
, and certain parts of Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
. This human-facilitated dispersion occurred mostly after ''L. trifolii'' became resistant to certain insecticide
Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...
s and therefore were not killed off by the exports' treatment with insecticides before and after transport.
Habitat
''L. trifolii'' are naturally found in tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
and subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...
regions. However, they frequently infest greenhouses and can now be found as an invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...
in a wider variety of climates. Because of this human-facilitated dispersion, ''L. trifolii'' can now be found in more temperate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
climates than they naturally would, although their development and survival is not as successful in the cooler climates.
Life History
Compared to other flies, ''L. trifolii'' have a relatively brief life cycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
*Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
* Life-cycle hypothesis ...
, ranging from 21 to 28 days in habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
s they are native to. Because of this, there can be multiple generations of ''L. trifolii'' within one year in warm climates. Additionally, the rate of development for ''L. trifolii'' has been shown to be temperature-dependent. Maximum pupal survival rates and oviposition
The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
rates were shown to occur at 30˚C.
Eggs
The eggs are typically about 1 mm long, 0.2 mm wide, and oval in shape. Initially after oviposition, the eggs are clear, but they become creamy white in color as time goes on. Eggs are laid just below the surface of the leaf; when the larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
e hatch, they mine their way out of the leaf as they feed, hence the name "leaf miner". The eggs frequently fall victim to parasitoid wasp
Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causin ...
s.
Larval Instars
The larvae of ''L. trifolii'' are unique from those of many other flies in their shape, as the body of ''L. trifolii'' larva does not taper at the head end. The larvae are uniform in thickness at both their anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
and posterior ends but additionally have a pair of spiracles at the posterior end. They do not have legs and are initially clear in color, but gradually become yellow as they mature.
The larval instar
An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...
s are differentiable by the lengths of the body and mouthparts. The first instar is recognizable by a mean body length of 0.39 mm and a mouthpart length of 0.10 mm. For the second instar, the mean measurements are 1.00 mm (body) and 0.17 mm (mouth). For the third instar, the mean measurements are 1.99 mm (body) and 0.25 mm (mouth). The fourth instar is a non-feeding stage and thus is usually disregarded.
Pupa
Typically, at the end of the larval phase, ''L. trifolii'' drop to the soil to pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
te after exiting the leaf mines they have created. Initially, the pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
rium is yellow, but it grows to become a darker brown over time. The puparium is typically less than 2.3 mm long and 0.75 mm wide.
Adults
Adult female ''L. trifolii'' tend to live around 13 to 18 days. Male adults typically only live 2 to 3 days because they are unable to puncture plants and thus have difficulty feeding. As previously described, both males and females are typically around 2 mm in length with a wingspan around 1.25 mm. After chewing a fan shape into the leaf of their host plant, adults feed on exuding sap
Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant.
Sap is distinct from latex, resin, or cell sap; it is a separa ...
of the host plant on which oviposition will occur.
Food Resources
Both larval and adult female ''L. trifolii'' feed primarily on the leaves of their host plants. Larvae feed mostly on the layer of the leaf just below the epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
, while female adults feed on liquids expelled by the leaves after the adult has punctured them. ''L. trifolii'' feed on a large variety of host plants, including both vegetables and ornamental plants. Studies on the flies' preferred hosts show that some of ''L. trifolii'''s most preferable hosts are chrysanthemum
Chrysanthemums (), sometimes called mums or chrysanths, are flowering plants of the genus ''Chrysanthemum'' in the family Asteraceae. They are native to East Asia and northeastern Europe. Most species originate from East Asia and the center ...
s, Gerber daisies, and celery
Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, lea ...
. When the females are placed on preferable hosts, they produce more holes and show an increased rate of oviposition.
Mating
The ways in which ''L. trifolii'' signal readiness for mating are not entirely known. Researchers have not reported the presence of any sex pheromones, but ''L. trifolii'' may attract mates and signal readiness through a series of short-distance vocalization by the males. This vocalization also manifests into male ''L. trifolii'' rapidly "bobbing" up and down when nearby to females they would like to mate with.
Males are typically not overly aggressive, but aggression between ''L. trifolii'' males has been observed in severely overcrowded laboratory conditions. During copulation, if a rival male approaches a pair, the mating male will repeatedly flex his wings until the rival is scared away. This is likely a display of his fitness through his wing size.
Parental Care
Oviposition
Oviposition occurs within 24 hours of mating
In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reproduc ...
, usually during daylight
Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunligh ...
hours. When oviposition is going to occur, the female punctures the host leaf in a tubular shape, feeding on the sap
Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant.
Sap is distinct from latex, resin, or cell sap; it is a separa ...
released from the leaf as she punctures. Oviposition typically occurs at a rate of 35 to 39 eggs per day. Females often lay a total of 200 to 400 eggs in their lifetime when on ideal hosts such as celery
Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, lea ...
. Both the rate of oviposition and the total fecundity
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
decrease when located on less ideal host plants, such as tomato
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...
es.
Site Selection For Egg Laying
Eggs are typically oviposited on leaves toward the center of the host plant. Regardless of host plant, the female's first action is bending of the abdomen to position her ovipositor at the correct angle to the leaf. The ovipositor than contacts the leaf in a series of "rapid thrusts". The female punctures the leaf in either a fan shape or a tubular shape. The eggs are inserted into the tubular punctures on the bottom surface of the host leaf, just below the epidermis. This is where the larva will create its mine upon hatching. Oftentimes, the mother will make multiple punctures before selecting the ideal spot. Oviposition rate is significantly increased for female ''L. trifolii'' located on ideal host plants such as celery
Celery (''Apium graveolens'') is a marshland plant in the family Apiaceae that has been cultivated as a vegetable since antiquity. Celery has a long fibrous stalk tapering into leaves. Depending on location and cultivar, either its stalks, lea ...
.
Enemies
Parasites
The most significant natural threat to ''L. trifolii'' are parasitoid wasp
Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causin ...
s. These wasps lay their eggs amongst the eggs of ''L. trifolii.'' When the wasps hatch, they typically devour the flies' nearby eggs, as is the defining characteristic of parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
s. The most common parasitoids of ''L. trifolii'' are wasps from the families Braconidae
The Braconidae are a family of parasitoid wasps. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species and many thousands more undescribed. One analysis ...
, Eulophidae
The Eulophidae are a large family of hymenopteran insects, with over 4,300 described species in some 300 genera. The family includes the genus '' Elasmus'', which used to be treated as a separate family, "Elasmidae", and is now treated as a s ...
, and Pteromalidae
The Pteromalidae are a very large family of mostly parasitoid wasps, with some 3,450 described species in about 640 genera (the number was greater, but many species and genera have been reduced by synonymy in recent years). The subfamily-level d ...
. In the absence of insecticides
Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...
, these parasitoids play a major role in keeping the ''L. trifolii'' population under control.
Predators
Although predators and diseases tend to impact the ''L. trifolii'' population to an insignificant amount compared to parasitoids, both larvae and adult ''L. trifolii'' can still be at risk of predation by general predators. The most common predators of ''L. trifolii'' are ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...
s.
Interactions With Humans
''L. trifolii'' is a highly destructive pest of both produce
Produce is a generalized term for many farm-produced crops, including fruits and vegetables ( grains, oats, etc. are also sometimes considered ''produce''). More specifically, the term ''produce'' often implies that the products are fres ...
and ornamental plant
Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that i ...
s. They often infest greenhouse
A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of transparent material, such as glass, in which plants requiring regulated climatic conditions are grown.These ...
s and inhabit shipping container
A shipping container is a container with strength suitable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to the ubiquitous corrugated boxes. In the context of ...
s, making them an invasive species in several countries around the globe. Because of this, they are a quarantine species in several countries, meaning their host plants are isolated for testing when ''L. trifolii'' are found on them. ''L. trifolii'' are most destructive to floricultural crops, which are severely impacted by any insect damage. Leaf miner abundance is assessed using a variety of sampling methods, including counting mines, counting live larvae, collecting pupae, and capturing adults. ''L. trifolii'' can be destructive to crops in many ways, including spreading diseases, destroying seedlings, and altering leaf production, which damages the fruits. All of these impacts on the crops decrease their value, which can be catastrophic to the industry.
Insecticide Resistance
The spread of this pest is widely due to the fly's developed resistance to certain insecticides
Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...
. This has been a major issue combatted by attempts from the Florida Fruit and Vegetable Association (FFVA) to mitigate the infestation and spread of these pests. However, due to previous spreading of ''L. trifolii'' through exported goods, ''L. trifolii'' are already a major pest of ornamentals in California. The California chrysanthemum
Chrysanthemums (), sometimes called mums or chrysanths, are flowering plants of the genus ''Chrysanthemum'' in the family Asteraceae. They are native to East Asia and northeastern Europe. Most species originate from East Asia and the center ...
industry lost approximately $93 million to damage caused by ''L. trifolii'' in the 1980s. Insecticides also kill off parasitoids that inhabit the area. Thus, the use of insecticides not only damages the ecosystem, but also reduces the population of the main form of biological control
Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...
for ''L. trifolii''.
References
{{Taxonbar, from=Q4285103
Agromyzidae
Articles created by Qbugbot
Insects described in 1880
Endemic fauna of the Southeastern United States