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''Rhagoletis mendax'' is a species of tephritid fruit fly known by the common name blueberry maggot. The blueberry maggot is closely related to the
apple maggot The apple maggot (''Rhagoletis pomonella''), also known as the railroad worm (but distinct from the '' Phrixothrix'' beetle larva, also called railroad worm), is a species of fruit fly, and a pest of several types of fruits, mostly apples. Thi ...
(''R. pomonella''), a larger fruit fly in the same genus. It is a major pest of plant species in the
Ericaceae The Ericaceae () are a Family (biology), family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with about 4,250 known species spread acros ...
family, such as blueberry, cranberry, and huckleberry. The larva is 5 to 8 mm long, apodous, and white with chewing mouthparts. Female adults are 4.75mm in length, males are slightly smaller. Both adults are mostly black in color with white stripes, orange-red eyes, and a single pair of clear wings with black banding. The adult female fly lays a single egg per blueberry, and when the larva hatches it consumes the fruit, usually finishing the entire berry in under 3 weeks and rendering it unmarketable. The larva then falls to the soil and
pupa A pupa (; : 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 life cycle, the stages th ...
tes. Adult flies emerge, mate, and females
oviposit 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 ...
when blueberry plants are producing fruit. Each female fly can lay 25 to 100 eggs in their lifetime. It is present in regions of the eastern and southern United States and eastern Canada. The spread of infestation is regulated by national and regional plant protection organizations. These include the
Canadian Food Inspection Agency The Canadian Food Inspection Agency (CFIA; ) is a regulatory agency that is dedicated to the safeguarding of food, plants, and animals (FPA) in Canada, thus enhancing the health and well-being of Canada's people, environment and economy. The age ...
(CFIA), the
United States Department of Agriculture The United States Department of Agriculture (USDA) is an executive department of the United States federal government that aims to meet the needs of commercial farming and livestock food production, promotes agricultural trade and producti ...
(USDA), the
European and Mediterranean Plant Protection Organization The European and Mediterranean Plant Protection Organization (EPPO) is an Intergovernmental organization, intergovernmental organisation responsible for European cooperation in plant protection in the European and Mediterranean Sea, Mediterranean ...
(EPPO), and smaller regional government organizations. Blueberry maggot infestations are predominantly controlled with the use of chemical insecticides.
Degree day A degree day is a measure of heating or cooling. Total degree days from an appropriate starting date are used to plan the planting of crops and management of pests and pest control timing. Weekly or monthly degree-day figures may also be used wi ...
predictive models and monitoring data gathered through sticky card traps are used in an
integrated pest management Integrated pest management (IPM), also known as integrated pest control (IPC) integrates both chemical and non-chemical practices for economic control of pests. The UN's Food and Agriculture Organization defines IPM as "the careful consideratio ...
program to make decisions on timing and frequency of control applications. Cultural measures such as removing overripe berries are often paired with chemical insecticide treatments in control programs.


Morphology

Eggs are white and elongate in shape. Full-grown larvae or maggots are long, off white, with large preoral teeth (in front of the mouth), a cone-shaped distal sensory organ at the head, and large anal lobes and paired spiracles located on the blunt posterior. The pupa is encased in a brown outer skin known as a
pupa A pupa (; : 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 life cycle, the stages th ...
rium. Adults are the most distinguishable of the life stages from other ''Rhagoletis'' species - mainly by the ratio of banding on their wings, ovipositor length and other genital features - and can be identified using a taxonomic
identification key In biology, an identification key, taxonomic key, or frequently just key, is a printed or computer-aided device that aids in the identification of biological organisms. Historically, the most common type of identification key is the dichotomous k ...
. The female fly is approximately long with a wingspan of , with male flies being slightly smaller. The
thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...
of both males and females is mostly black with a conspicuously white spot covering the scutellum and a white stripe on either side. The abdomen of females is pointed and has four horizontal bands of fine white
seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...
e separating the sections, while the male abdomen is more rounded and has only three horizontal bands of setae. The head is almost entirely covered by the eyes which are red in color, with a protruding pair of aristate antennae. They possess a single set of wings, which are clear with conspicuous dark black bands arranged in an "F" pattern. In many cases, visually distinguishing stages of ''R. mendax'' from others in the ''pomonella'' species group is not possible and may require the use of biochemical tests such as PCR to conclusively determine the species.


Life cycle

The life cycle of this species is
holometabolous Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphic trait of all insects in the clade Holometabola. Immatur ...
, and has four stages of development: egg, larva, pupa and adult. Adults typically have a lifespan of 30–45days or longer, with females being capable of reproduction starting at 15days and going to approximately 45days (weather dependent). The
phenology Phenology is the study of periodic events in biological life cycles and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors (such as elevation). Examples include the date of emergence of leav ...
of the blueberry maggot is varied, and depends on the geographic region the population inhabits. In most regions of North America, populations have a
univoltine Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. The term is most often applied to insects, and is particularly in use in sericulture, where silkworm varieties vary in their voltinism. ...
life cycle. In Maine and potentially other locations however approximately 85% of the population in the state is
univoltine Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. The term is most often applied to insects, and is particularly in use in sericulture, where silkworm varieties vary in their voltinism. ...
, while the rest are semivoltine: 10% spend three winters as pupae, and 5% spend four winters. In the spring or summer the first wave of adults will emerge from the soil, coinciding with or just before ripening of the host fruit in the region. Adults will continue emerging in groups into the summer. Approximately 90% of the population emerges within a one-month period of each other, however, females will emerge 4–5days before males at the time of maximum fruit availability. Emergence is delayed to summer in some areas, potentially due to heat-induce
quiescence
of pupae. Adults will feed on dew, insect honeydew, and other secretions on foliage until the females become sexually mature. After mating, female flies will lay a single egg per berry using a retractable
ovipositor 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 typica ...
on the end of their abdomen to pierce the fruit and deposit the egg just under the skin. The process leaves behind an oviposition-deterring pheromone to prevent other females from laying their egg in the same fruit for a couple of days. Eggs will hatch in 3–7days depending upon geographic location and climate, and the larvae will begin consuming the fruit. Larvae will continue to feed and go through three
instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...
s of growth in 17–30days, at which point third instar larvae will emerge from the fruit, drop to the soil, and begin pupating at a depth of . Pupation can commence in July at the southernmost limits of its distribution and into late September at its northernmost limits.


Distribution

''Rhagoletis mendax'' is native to North America, and is found in the eastern regions of the United States and Canada. As of 2015 in the United States its distribution reaches as far south as states such as Georgia and Florida, and as far northwest as states such as Maine and Vermont. In Canada, it is present in all coastal eastern provinces excluding Newfoundland and Labrador (
New Brunswick New Brunswick is a Provinces and Territories of Canada, province of Canada, bordering Quebec to the north, Nova Scotia to the east, the Gulf of Saint Lawrence to the northeast, the Bay of Fundy to the southeast, and the U.S. state of Maine to ...
,
Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...
,
Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...
, &
Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
), and only in small populations in Quebec and Ontario. The primary mode of dispersal to new areas is through transport of infected fruit, and secondly through flight, as ''R. mendax'' adults can only fly short distances. Pupae can also be transported in contaminated growing media.


Hosts and feeding behavior

''Rhagoletis mendax'' adults are attracted to a wide range of species in their host genus
Ericaceae The Ericaceae () are a Family (biology), family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with about 4,250 known species spread acros ...
, and prefer them to the hosts of other ''Rhagoletis'' species. Of the Ericaceae genera, many hosts are commercial crops and wild species of the genus ''
Vaccinium ''Vaccinium'' is a common and widespread genus of shrubs or dwarf shrubs in the heath family (Ericaceae). The fruits of many species are eaten by humans and some are of commercial importance, including the cranberry, blueberry, bilberry (wh ...
'', such as highbush and lowbush blueberries (''V. corymbosum'' & ''angustifolia'' respectively), cranberries (''V. macrocarpon''), lingonberries (''V. vitis-idaea''), and huckleberries (''Vaccinium sp.'' & ''Gaylussacia sp)''. Some research shows that adults are also attracted to volatiles secreted by ''Enterobacter'' (''Pantoea'') ''agglomerans,'' an epiphytic nitrogen-fixing species of bacteria found on the leaves and fruit of plants. This may be due to a symbiotic relationship between the two species, where ''E. agglomerans'' provides nitrogen necessary for maturation of the female's ovaries.


Impact

Larva feeding on berries from within can result in premature fruit drop and loss of structural integrity. Additionally, the presence of larvae in commercially grown berries can negatively impact consumer satisfaction. These factors lead to loss of marketability of the fruit and a reduction in profits for the grower.


Controls


Degree day models

Degree day A degree day is a measure of heating or cooling. Total degree days from an appropriate starting date are used to plan the planting of crops and management of pests and pest control timing. Weekly or monthly degree-day figures may also be used wi ...
predictive modelling based on the temperature of the soil is used to determine the most likely dates of adult emergence in the area. The developmental threshold for ''R. mendax'', the minimum temperature required for individuals to continue maturing, is . Degree Day Models from the University of Maine predict that the middle of fly population emergence can be predicted by the accumulation of 971 °F
degree day A degree day is a measure of heating or cooling. Total degree days from an appropriate starting date are used to plan the planting of crops and management of pests and pest control timing. Weekly or monthly degree-day figures may also be used wi ...
s (accumulations period in which the average daily temperature is at or above the developmental threshold) from April 1. Computer programs that calculate the date of phenological occurrences based on inputted temperature data, such as the middle of ''R. mendax'' emergence, are offered by some universities such as the University of Maine as an extension service. This information is used in combination with monitoring data in
integrated pest management Integrated pest management (IPM), also known as integrated pest control (IPC) integrates both chemical and non-chemical practices for economic control of pests. The UN's Food and Agriculture Organization defines IPM as "the careful consideratio ...
programs to determine the timing and effectiveness of control tactics, such as pesticide application, to increase effectiveness.


Monitoring

Yellow sticky cards folded into a v-shape, baited with ammonium acetate on the exterior, and hung between crop plants are most commonly used to detect the presence of ''R. mendax'' in a commercial berry field. Traps set in a grid pattern allow for more precise measurements of where in the field populations are located.


Cultural

Removing over-ripe fruit from fields can lower the number of adults that will emerge the following spring and reduce the rates of re-infestation.


Chemical

Insecticides with short environmental persistence are recommended to control the adult stage. No pesticides can effectively target the larval or pupal stages, as they are protected by a fruiting body and soil respectively. The recommended application time is 5–7days after catching the first adult fly, with spot and perimeter treatments being effective where there are few but heavily infested areas of the field. Trials conducted by Michigan State University found pesticides with the active ingredient spinosyn were rated good-excellent in controlling populations of blueberry maggot in fields with acute infestations. Attract-and-kill style traps are being tested for potential use as a control method for ''R. mendax'', having been successfully used to control the
apple maggot The apple maggot (''Rhagoletis pomonella''), also known as the railroad worm (but distinct from the '' Phrixothrix'' beetle larva, also called railroad worm), is a species of fruit fly, and a pest of several types of fruits, mostly apples. Thi ...
(''R. pomonella''). Traps composed of biodegradable and regular plastic, or matted paper are baited with an ammonia-based
kairomone A kairomone is a semiochemical released by an organism that mediates interspecific interactions in a way that benefits a different species at the expense of the emitter. Derived from the Greek καιρός, meaning "''opportune moment""kairomon ...
lure, an attractive color, or both, and treated with an insecticide. Death results from contact and ingestion of the insecticide. The insecticidal compounds
imidacloprid Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects. The chemical works by interfering with the transmission of stimuli in the insect nervous system. ...
and
fipronil Fipronil is a broad-spectrum insecticide that belongs to the phenylpyrazole insecticide class. Fipronil disrupts the insect central nervous system by blocking the ligand-gated ion channel of the GABAA receptor ( IRAC group 2B) and glutamate-g ...
yielded the highest rate of ''R. mendax'' adult fly death in one study.


Regulation

The
Canadian Food Inspection Agency The Canadian Food Inspection Agency (CFIA; ) is a regulatory agency that is dedicated to the safeguarding of food, plants, and animals (FPA) in Canada, thus enhancing the health and well-being of Canada's people, environment and economy. The age ...
(CFIA), the national plant protection organization of Canada, created directiv
D-02-04
for the use of government agencies such as the
United States Department of Agriculture The United States Department of Agriculture (USDA) is an executive department of the United States federal government that aims to meet the needs of commercial farming and livestock food production, promotes agricultural trade and producti ...
- Animal and Plant Health Inspection Service (USDA-APHIS) and
Canadian Border Services Agency The Canada Border Services Agency (CBSA; , ''ASFC'') is a federal law enforcement agency that is responsible for border control (i.e. protection and surveillance), immigration enforcement, and customs services in Canada. The CBSA is responsib ...
(CBSA), and private businesses such as growers and importers. It outlines recommended phytosanitary measures to prevent the spread of ''R. mendax'' in fresh blueberries and blueberry plants. Additionally, the CFIA conducts a yearly blueberry maggot survey in non-regulated areas of Canada. Participating commercial blueberry fields are monitored using baited sticky cards in areas where the pest is not present or present in low populations to ensure the "pest-free status" of these areas. ''Rhagoletis mendax'' is regulated as a quarantine pest by the European and Mediterranean Plant Protection Organization (EPPO) under the A1 quarantine list category 'non-European Trypetinae' flies. This is used as a trade restriction for imported commodities such as fresh fruit and host plants.


References


External links


Species descriptionPhotos and diagrams
{{Taxonbar, from=Q7320116 mendax Agricultural pest insects Insects described in 1932