User:Stefanija Kovacevic/Rhagoletis mendax

Rhagoletis mendax is a species of tephritid fruit fly known by the common name blueberry maggot. It is a major pest of blueberry crops in the eastern and southern United States and eastern Canada, and is listed as a non-quarantine pest of concern by the Canadian Food Inspection Agency. It attacks several species of blueberry (Vaccinium angustifolium & V. corymbosum) and related species. The larva is 5 to 8 mm long, apodous, and white with chewing mouthparts. Female adults are 4.75mm in length with slightly smaller males, and both are mostly black in color with white stripes, orange-red eyes, and a single pair of clear wings with black banding. The fly is destructive to fruit when it is a larva. 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. The larva then falls to the soil and pupates. Adult flies emerge, mate, and females oviposit when blueberry plants are producing fruit. Each female fly can lay 25 to 100 eggs in their lifetime.

The blueberry maggot is closely related to the apple maggot (R. pomonella), a larger fruit fly in the same genus. Blueberry maggot infestations are generally controlled with the use of chemical insecticides.

Morphology

Eggs are white and elongate in shape. Full-grown larvae or maggots are 7.75mm (5/16 inches) 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 puparium. 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. The female fly is approximately 4.75 mm (3/16 inch) long with a wingspan of 8mm (1/3 inch), with male flies being slightly smaller. The thorax 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 setae 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

Life Cycle of Rhagoletis Mendax

The life cycle of this species is holometabolous, and has four stages of development: egg, larva, pupa and adult. Adults typically have a lifespan of 30-45 days or longer, with females reproductive period starting at 15 days and going to approximately 45 days (weather dependent).

The phenology of the blueberry maggot is varied, and depends on the geographic region the population inhabits. In most of North America populations have a univoltine life cycle, whereas in Maine and potentially other locations approximately 85% of the population in the state is univoltine, while the rest are semivoltine: 10% spend three winters as pupae, and 5% four winters.

In the spring or summer adults will emerge from the soil, coinciding with or just before the host fruit in the region ripens. Approximately 90% of the population emerges within a one-month period of each other, however females will emerge 4-5 days before males at the time of maximum fruit availability. Emergence is delayed to summer in some areas, potentially due to heat-induced quiescence of pupae.

After mating, adult female flies will lay a single egg per berry using their ovipositor to pierce and deposit the egg just under the skin of the fruit, leaving behind an oviposition-deterring pheromone to prevent other females from laying their egg in the same fruit for a couple of days.

The egg will hatch in 3-7 days depending upon geographic location and climate, and the larva will begin consuming the fruit. Larvae will continue to feed and go through three instars of growth in 17-30 days, at which point the third instar emerges from the fruit, drops to the soil, and begins pupating. Pupation can commence in July at the southernmost limits of its distribution and into late September at it's Northernmost.

Distribution and Habitat

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 it's 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, 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 generally only fly short distances. Pupae can also be transported in contaminated growing media.

Hosts and Feeding Behavior

R. mendax adults are attracted to a wide range of species in their host genus Ericaceae, and prefer them to hosts of other Rhagoletis species.

Of the Ericaceae genus, many hosts are cultivated crops and wild species of the Vaccinium genus, 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.

Impacts

Maggots feeding on berries from within can result in premature fruit drop and loss of structural integrity. Additionally, presence of maggots in the berry can negatively impact consumer satisfaction. These factors lead to loss of marketability of the fruit and impacted profits of the grower.

Controls

Degree-day predictive modelling based on the temperature of the soil is used to determine the most likely dates of adult emergence in the spring. This information is factored into pest control programs to make pesticide application more targeted.

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 presence of R. mendax in a commercial field.

Cultural

Removing over-ripe fruit from fields can lower the number of adults that will emerge next spring, reducing 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 5-7 days after catching the first adult fly. 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.

Regulation

R. mendax is regulated as a quarantine pest by the European and Mediterranean Plant Protection Organization (EPPO) under the A1 quarantine list category 'non-European Tyrpetidae' flies. This is used as a trade restriction.

The Canadian Food Inspection Agency 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.

References

Base article copied from Rhagoletis mendax - Review R. pomonella article for introduction summary.

Leads to follow up o

Handbook of the Fruit Flies (Diptera: Tephritidae) of America North of Mexico. Richard H. Foote , F. L. Blanc , Allen L. Norrbom - https://doi.org/10.1086/418796 ($5)

Government of Canada (Distribution and Life Cycle Diagram) - https://www.inspection.gc.ca/plant-health/plant-pests-invasive-species/insects/blueberry-maggot/fact-sheet/eng/1328330175586/132330543631

Journal of Integrated Pest Management, Review of Blueberry Maggot Fly (very reliable-looking source) - https://academic.oup.com/jipm/article/6/1/11/2936978

Rutgers University (Pesticide Effectiveness Ratings) - https://plant-pest-advisory.rutgers.edu/blueberry-pest-in-detail-blueberry-maggot/

University of Maine (Prediction, Controls, Scouting and Alternative Treatments) - https://extension.umaine.edu/blueberries/factsheets/insects/201-monitoring-for-the-blueberry-maggot/

University of Florida, "Featured Creatures" - http://entnemdept.ufl.edu/creatures/fruit/blueberry_maggot.htm

CABI - https://www.cabi.org/isc/datasheet/47057

CFIA regulated species - https://www.inspection.gc.ca/plant-health/plant-pests-invasive-species/insects/blueberry-maggot/eng/1328325206503/1328325288221 & https://www.inspection.gc.ca/plant-health/plant-pests-invasive-species/directives/date/d-02-04/eng/1320046578973/1320046750986

CFIA blueberry certification program against BM - https://www.inspection.gc.ca/plant-health/plant-pests-invasive-species/directives/horticulture/d-02-04/eng/1320046578973/1320046655958

CABC. Control strategies and natural enemies leaflet. https://cdn.dal.ca/content/dam/dalhousie/pdf/faculty/agriculture/oacc/en/technical-bulletins/2008/OACC_Technical_Bulletin_2008_44_web.pdf