Because C. capitata has such negative impact on agricultural economies around the world, research into cotrol of this species is widespread. An important step in limiting crop damage inflicted by medflies is field sanitation. This involves destroying unmarketable and infested fruits, burying them one meter under soil with lime to kill any larvae present in the fruit. Also, reducing food sources (i.e. keeping the quantity of ripe fruit to a minimum) through weekly harvestings is helpful. In areas of severe infestation, further techniques are needed to eliminate medflies.
Insecticides are used, but can be ineffective since egg-laying takes mere minutes. Although the chemicals kill the adult pests, they often work only after eggs have been laid. Bait insecticides containing proteinaceous liquid attractants encourage females to feed. Such females may die before oviposition, reducing crop damage caused by larvae. Disadvantages of insecticide use include: residues in food, soil and water pollution, and the evolution of resistance to pesticide in medfly populations.
Releasing parasitoids (such as the wasps mentioned under “Predators”) is another method of control that may be employed. Research conducted in Hawaii showed that approximately twenty thousand wasp parasitoids (Diachasmimorpha tryoni) per square kilometer per week provided effective medfly suppression.
One of the most successful techniques of control, especially in combination with the release of parasitoids, is the release of sterile males. These sterile males mate with wild females who, in turn, produce infertile eggs.Such eggs do not hatch into destructive larvae. Difficulties in the production of sterile males have limited the utility of this method.
There is sometimes confusion between C. capitata and other species of "true fruit flies" (family Tephritidae) and Drosophila macquarti, the "fruit fly" that has been widely used in genetic research (along with other species of Drosophila). Despite the similar common names, Drosophila is in a different family, the Drosophilidae, and is not a significant agricultural pest. The Drosophila species that feed on fruit feed mainly on yeasts and other microbes that grow on decaying fruit, not on the fruit itself. They may be a household nuisance, but unlike Ceratitis capitata and other tephritids, they don't damage intact fruit.
These flies have no obvious structures or behaviors that are specifically related to defense against predators.
Medflies are attached by many parasitoid wasps. Some wasps (such as Diachasmimorpha tryoni and Diachasmimorpha longicaudata) are capable of hearing the larvae eating their way through the fruit. The wasp uses its ovipositor to inject an egg into the maggot. During the fly's pupation, the wasp larva will eat its host, killing the developing fly and emerging from the pupal case as an adult.
Many generalist predators of insects, such as ants, spiders, mantids, and assassin bugs will attack fruit flies. Birds, including chickens, will attack the larvae as they emerge from fruit, and some soil nematodes attack the larvae as the burrow and pupate.
Known Predators:
The body of C. capitata is protected by an exoskeleton made of chitin. As in all insects, the body has three main segments: the head, thorax, and abdomen; as well as three pairs of legs. The oval-shaped abdomen is yellowish with two white bands. It is covered by black bristles. The thorax is whitish-yellow with patches of black. The eyes are reddish-purple, transforming to black within 24 hours of death. The single pair of wings is translucent and embellished with patterns of brown, yellow, black, and white.
Medflies exhibit sexual dimorphism in that females are larger than males and can be identified by a yellow wing pattern and pointed ovipositor (about 1.2 mm long) which is used to plant eggs within the host fruit. Males have more exaggerated features such as more brightly colored eyes, longer front legs, and a pair of supra-fronto-orbital bristles.
The white larvae, or maggots, are legless and may be up to 8 mm in length. Pupal length is about 4 mm and adults range from 3 to 5 mm, approximately two-thirds the size of a housefly. The wingspan of C. capitata was not available, but can be extrapolated from the wingspan of similar species. Oriental fruit flies, which have a body length of 6 to 8 mm, have a wingspan of 5.3 to 7.3 mm. Medflies, being slightly smaller in body size, probably have slightly shorter wingspans.
Range length: 3 to 5 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger; sexes colored or patterned differently; male more colorful
Sources differ on the maximum lifespan of adult medflies, it may be six months or a year, though they agree that cool conditions with abundant food and water are necessary for the flies to survive this long. Most live much shorter lives, and in most populations at least half are dead in less than 60 days. On a normal diet of sugar and protein in laboratory settings, females tend to outlive males by approximately 1.5 days.
Typical lifespan
Status: wild: 20 to 60 days.
Average lifespan
Status: wild: 35 days.
Typical lifespan
Status: captivity: 30 to 65 days.
Average lifespan
Status: captivity: 45 days.
In their native home range (sub-Saharan Africa), medflies are found in forests, open woodland in highland areas, and at the coast, shrublands, and dunes. Their dispersal across suboptimal habitats, such as areas where woody vegetation is dominant, is possible because of their ability to both exploit plants in dry habitats and their ability to migrate over moderate-to-substantial distances.
Ceratitis capitata hcan be found in agricultural areas where large quantities of fruit provide plenty of food. This species is widespread and may be found anywhere from sea level to mountainous areas (over 2,133 m in elevation). Its habitat use maybe be affected by other fruit fly species: when first introduced to Hawaii, medflies were found in the lowlands but since the subsequent introduction of the oriental fruit fly (Bactrocera dorsalis) in 1945, they are only found at higher elevations.
Range elevation: 0 to 2133 m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest ; rainforest ; scrub forest ; mountains
Other Habitat Features: agricultural
The oldest populations of mediterranean fruit flies (a.k.a. medflies) can be traced back to the African tropics in the Ethiopian biogeographic region. This species is native to both the Ethiopian and Palearctic regions, and introduced populations have since been discovered in all of the biogeographic regions.
Transportation of fresh fruit by air (either commercially, or incidentally by travelers) has greatly increased the risk of accidental introduction of this species into other parts of the world, and strong efforts are made to prevent its spread.
Biogeographic Regions: nearctic (Introduced ); palearctic (Native ); oriental (Introduced ); ethiopian (Native ); neotropical (Introduced ); australian (Introduced ); oceanic islands (Introduced )
Other Geographic Terms: cosmopolitan
Among the Tephritidae, medflies are the most polyphagous species. This means that they feed from the widest variety of host-fruits. Over 200 types of fruits and vegetables have been recorded as hosts for this parasitic species. Species consumed include fruits of the following plant families: Anacardiaceae, Cucurbitaceae, Loganiaceae, Meliaceae, Oleaceae, Podocarpaceae, Rosaceae, Rubiacaea, Sapotaceae and Solanaceae. Though preferences differ geographically, thin-skinned, slightly hard, ripe, and succulent fruits are desirable.
Adult (mature) and larval (immature) stages differ in their feeding habits. As mentioned under “Development”, larvae eat their way through the fleshy host fruit. At this immature stage, nutrition is essential and will determine adult size, time of development, and the percentage of larvae that emerge. Studies have shown that diets with higher concentrations of glucose and sucrose lead to better development than those containing high starch or maltose concentrations. Adult medflies require carbohydrates from the juices of ripe fruit, and protein from bird feces and decomposing fruit. Adults feed in mid-morning and late afternoon.
Adult medflies prefer the portion of the fruit in which there is more nutritive value. For example, the lower portions of orange and papaya fruits contain the bulk of the nutrition. If placed on the top portion of these fruits, a medfly will move to the lower part. In contrast, flies placed on the lower portion of the fruit remain there to feed.
Plant Foods: fruit; sap or other plant fluids
Other Foods: dung
Primary Diet: herbivore (Frugivore )
In their natural environment, these flies are parasitic on host plants, but are not often harmful to plant populations. They may reduce seed dispersal by spoiling fruit, but they don't necessarily prevent seed germination. They are prey for a wide variety of insect predators and parasites. They are much more significant in agricultural ecosystems, where they can be a major pest of fruit crops (see below).
Ecosystem Impact: parasite
Species Used as Host:
Mutualist Species:
Commensal/Parasitic Species:
There are no known positive effects of Ceratitis capitata on humans.
Of all true fruit flies, medflies are the most rampant pest, attacking practically all with a fleshy fruit species. Economically, medflies impact humans by damaging crops and making the fruit unmarketable.
Fruit-growers and their governments around the world spend millions of dollars a year trying to control this pest and prevent it from spreading to new locations.
Negative Impacts: crop pest
Medflies undergo a complete metamorphosis, beginning life as larvae and transforming into completely different-looking adult fruit flies. Females lay their eggs approximately 1 mm beneath the skin of host fruit. Although each female lays only 2 to 10 eggs in a given fruit, multiple females may lay their eggs in the same location, so that the slim, smooth, white eggs, about 0.1 cm long, may be clustered together in a single spot of seventy-five or more.
After 1.5 to 3 days (longer if the temperature is lower) the eggs hatch. The larvae carve tunnels, eating their way through the fruit. Larval life may last a mere 6 to 10 days (when temperature is around 25ºC). Along with temperature, the type of host fruit affects the length of the larval stage. In citrus fruits, 14 to 26 days may be required to reach pupation. Development in a green peach is completed in 10 to 15 days.
There are three larval stages, or instars. In the first, larvae are slender, cream colored, translucent, and about 0.1 cm long. In the second instar, larvae are partly transparent, revealing the fruit in the gut. By the third instar, larvae are opaque white and 0.6 to 0.8 cm long. These larvae can be distinguished from other fruit fly larvae by their thoracic spiracles, with 7 to 11 small protruding tubules.
Most larvae begin to pupate at sunrise, an inch or two into the soil. The pupal stage lasts from 6 to 13 days at around 24.4ºC. This range significantly increases (possibly to about 19 days) when the temperature drops to around 20.5ºC. The pupal stage is resistant to temperature extremes and dessication, so it may last much longer if conditions are not right for emergence. It is typical for the new adult medflies to surface on warm mornings. At this early adult stage, they are capable of flying short distances, and may disperse further distances via the wind.
Development - Life Cycle: metamorphosis
This species is abundant around the world, and not considered in need of conservation. It is a pest, and the target of strong efforts to reduce its abundance and distribution.
US Federal List: no special status
CITES: no special status
Male medflies use chemical, visual, acoustic, and behavioral (e.g. wing waving) signals in their sexual communication with females. See “Reproduction: Mating Systems” for information on both male-female and male-male (marking of leaves with chemical to stake out mating ground territory) communication. In addition to these communication pathways, it is likely that some tactile communication occurs during mating itself.
Communication Channels: visual ; tactile ; acoustic ; chemical
Other Communication Modes: pheromones ; scent marks ; vibrations
Perception Channels: visual ; ultraviolet; tactile ; acoustic ; vibrations ; chemical
Female medflies are fussy about their mates. Though the basis of a female's choice is not entirely understood by scientists, characteristic communications between the sexes are thought to play a role.
Male medflies claim their mating ground territories on individual leaves by depositing a pheromonal substance from the tip of the abdomen to the leaf. In addition, the male emits sounds by rapidly vibrating his wings while perched on the underside of his leaf.
Females watch this behavior from a distance of about 6 to 10 cm then begin to approach the male if he is deemed acceptable. As the female nears (within 3 to 5 mm) the male’s rapid wing flapping switches modes to what is called “fanning” in which he moves forward and backward, possibly to better direct the pheromones at the female. The male then proceeds with a side-to-side head motion. Slow motion analysis of the courtship shows female responses to the calling male. These inconspicuous responses, all occurring within 0.04 to 0.16 seconds, include touching the male with her head or front legs, jumping towards the male, short wing vibrations, and stretching just after mounting. A female may reject a male at any stage of the courtship sequence.
Males seek multiple mates (polygyny), whereas females tend to remate only if the initial mating was with a sterile male.
Mating System: polygynous
Adult medflies reach sexual maturity approximately five days after emerging from the pupal stage. Copulation occurs at any time of the day and both sexes are sexually active throughout the entire day. Medflies in tropical regions (warm temperatures year round) are capable of year-round breeding. A female medfly may lay up to 22 eggs per day, and possibly 800 eggs during her lifetime, though 300 is more typical. Because new eggs are constantly made throughout a female’s adult life, fecundity, or the number of eggs laid, is largely a function of the female’s lifespan.
Breeding interval: Female medflies usually mate once, then lay eggs over a period of several days or weeks before they die.
Breeding season: Medflies are capable of year-round breeding in tropical regions where the temperature remains warm. Otherwise, they breed during the warmer months of the year.
Range eggs per season: 200 to 800.
Average eggs per season: 300.
Range time to independence: 0 to 0 minutes.
Range age at sexual or reproductive maturity (female): 5 (low) days.
Range age at sexual or reproductive maturity (male): 5 (low) days.
Key Reproductive Features: semelparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous ; sperm-storing
Medflies do not provide care for their offspring after eggs have been laid. However, females do invest some resources in each egg, providing young with the nutrients and energy needed to hatch out as larvae.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female)
Ceratitis capitata, commonly known as the Mediterranean fruit fly or medfly, is a yellow-and-brown fly native to sub-Saharan Africa. It has no near relatives in the Western Hemisphere and is considered to be one of the most destructive fruit pests in the world.[1] There have been occasional medfly infestations in California, Florida, and Texas that require extensive eradication efforts to prevent the fly from establishing itself in the United States.[1]
C. capitata is the most economically important fruit fly species because of both its ability to survive cooler climates more successfully than most other fly species and its ability to inhabit more than 200 tropical fruits and vegetables to which it causes severe destruction and degradation.[1] The practices that are used to eradicate the medfly after its introduction into a new environment can be extremely difficult and expensive, but infestation of C. capitata lowers crop yields and induces costly sorting processes for fresh fruits and vegetables.[1]
C. capitata eggs are characterized by their curved shape, shiny white color, and smooth features.[1] Each egg is approximately 1 millimetre (5⁄128 in) in length.[1] As seen in other fruit flies, the egg possess a micropylar region with a clear tubular shape.[1]
Larvae of C. capitata have been described as having a common fruit fly larval shape that is cylindrical with a narrow anterior end and flattened caudal tail.[1] By the end of the third and final instar of the medfly, the larvae measure between 7 and 9 millimetres (35⁄128 and 45⁄128 in) and about 8 fusiform areas.[1]
The adult flies typically measure 3 to 5 millimetres (15⁄128 to 25⁄128 in) in length. There are numerous visually defining characteristics of the C. capitata’s bodily features. The thorax is a creamy white to yellow with a characteristic pattern of black blotches, and the abdomen is tinted brown with fine black bristles located on the dorsal surface and two light bands on the basal half. The medfly's wings contain a band across the middle of the wing with dark streaks and spots in the middle of the wing cells.
In a study done by Siomava et al., researchers utilized geometric morphometrics to analyze wing shape in three different fly species including C. capitata. Through their findings, the researchers showed that the medfly exhibits extensive sexual shape dimorphism (SShD) between the proximal and distal part of the wing. This difference can be used to distinguish between the two sexes since male wings tend to be wider and shorter in comparison to females. This anatomical difference is important because this allows males to displace more air and create a more audible “buzzing” effect during mate attraction.[1][2]
The Geographic Distribution Map of C. capitata (Updated December 2013).
The above map provides information on the distribution of the Mediterranean fruit fly, C. capitata, throughout the world. The information is mainly based on available Mediterranean fruit fly national surveillance reports. Therefore, the map displays assessments of the presence of this pest at the national level and in some cases at sub-national levels. According to this map, C. capitata is present throughout Africa, South and Central America, the Middle East, and Southern Europe. It has been confirmed to be absent in much of North America, the Indian subcontinent, some parts of South America, and most of Australia. Climate change might have role in modifying the distribution and abundance of C. capitata.[3]
The four stages of the C. capitata life cycle are the egg, larvae, pupae and adult stages. Female medflies oviposit in groups of roughly 10-14 eggs and deposit them just under the skin surface of their host fruit.[1] Once the eggs are deposited below the skin, they hatch in only a few days, emerging as maggots, or larvae. C. capitata flies are known to disperse up to distances of 12 miles in search of host fruit. In the instances where host fruit is plentiful in their current locations, they will not disperse beyond 300 to 700 feet.[2]
Medflies can complete their life cycles in 21 days in optimum conditions. In cooler temperatures, the life cycle of the medfly can take up to 100 days to complete. In temperatures that are below 50 °F (10 °C), development of the fly ceases. Oviposition in females ceases to occur in temperatures below 60 °F (16 °C).[1]
The lifespan of the C. capitata is quite short as half of most populations die in under 60 days. However, cool conditions and proper sustenance can enable some flies to live 6 months or up to a year. In lab conditions, under controlled diets of sugar and protein, the life expectancy of females is usually longer than that of males by 1.5 days. On average, the lifespans of flies in captivity are 10 days longer than those of wild flies.[4][5]
The lifespans of certain species are also affected by periods of food deprivation, which is a key driver of invasion success, adaptation, and biodiversity. Starvation resistance is a plastic trait that varies due to the relation between environmental and genetic factors. Recent studies into the starvation resistance (SR) of C. capitata has found that SR decreases with increasing age and that age-specific patterns are shaped in relation to adult and larval diet. Furthermore, females exhibited higher SR than males, and the greatest influence on SR in C. capitata was due to age and adult diet followed by gender and larval diet.[6]
Among fruit fly species, C. capitata has the largest variety of host-fruits, including over 200 different types of fruits and vegetables. These fruits include but are not limited to akee, star apple, oranges, grapefruit, guava, mango, plum, and pears.[7] C. capitata in the adult and larval stage feed in different ways.[4][7]
Because nutrition is a crucial determinant of adult size and development, larva prefer to eat fleshy host fruit. Higher concentrations of glucose and sucrose boost development and the percentage of emerging larva in comparison to high starch and maltose diets.[4][7][8]
By manipulating larval diets with relation to brewer's yeast and sucrose, researchers were able to show that varying the levels of yeast and sucrose in the diet changes the proportion of proteins to carbohydrates which affects the ability of pupating larvae to accumulate lipid reserves. Diets with high protein to carbohydrate ratios produced larvae with high protein and lipid contents. Conversely, diets with a low protein to carbohydrate ratio led to pupating larvae having relatively reduced loads of lipids.[9] Parental condition may affect larval responses to the immediate dietary environment through a process known as maternal effects.[10]
Research into the correlation between citrus variety, fruit part and stage of C. capitata has found strong effects on larval performance, smaller effects on pupae, and no effects on eggs. The highest survival rate was shown to be on bitter oranges; however, the shortest developmental time and heaviest pupae were obtained from orange cultivars. In short, pulp chemical properties such as acidity and soluble solid contents had little effect on larval and pupal survival but larger effects on pupal weight.[11]
Adults tend to gain their carbohydrate intake from ripe fruit and protein from decomposing fruit or leftover bird feces. While larva prefer the middle of the fruit, adults prefer the fruit portion that contains more nutritional value in comparison to the flesh. Their diet preferences have been proven by studies in which medflies placed at the top of oranges and papayas consistently moved lower to the nutrient dense parts whereas flies placed near the bottom remained in their starting location. Adult flies typically feed in the mid-morning/late afternoon.[4][7]
With respect to reproductive success of male C. capitata, males that are fed a diet consisting of no protein copulated at a significantly lower rate than males who were fed protein. In short, male diets are a significant factor in the mating success of male C. capitata as dictated by the receptivity of females to further copulations.[9]
It was shown, that adults of C. capitata host diazotrophic bacteria from the Enterobacteriaceae family in their gut. These symbionts actively fix nitrogen by the enzyme nitrogenase which can alleviate nitrogen limitation and thus can be beneficial for the host.[12]
Field observations conducted in various localities within the Hawaiian Islands, specifically in Kula, Maui and in Kona, Hawaii, showed researchers a clear distinction in the mating behavior of C. capitata. The mating ritual in this species of fly can be separated into two basic phases: (1) lek behavior and (2) courtship.
In lek behavior, males begin by acquiring territory and jockeying with each other for optimal position. Leks are always located in positions that optimize the amount of sunlight penetrating the leaves.[13] Mating in the C. capitata fly typically begins with males stationed at the bottom of the surface of leaves during the late morning or early afternoon. Once males are stationed at these locations, they begin the mating process by forming leks and releasing sex pheromones to attract virgin females. If successful, mating will occur during this time period. Another important location for copulation is on the fruit itself during the late morning or early afternoon. Males position themselves here in an attempt to copulate with already-mated females through seduction or force.[14] A study conducted by Churchill-Stanland et al., showed that a male's size can dictate their mating success rate. Researchers found that flies weighing approximately 8–9 mg had optimum mating success while smaller flies (i.e. <6 mg) had significantly less mating success.[1] Furthermore, when males were equal or larger in size, mating frequency was equal and events such as eclosion, flying, and mating speed were positively correlated with pupal size.[15]
During the courtship phase, a series of signals are exchanged between the male and the female. As the female approaches, the male tucks his abdomen under his body with his abdominal pouches still inflated and wings still vibrating. Once the female is within 3–5 millimetres (15⁄128–25⁄128 in) of the male, the male will begin a series of head movements. Within 1–2 seconds of head movement initiation, the male begins rhythmically wing its fannings and moves closer to the female. Once close enough, the male then leaps onto the females back and begins copulation.[13]
It has been shown that during mating, females experience a switch in olfactory-mediated behaviors. Specifically, virgin females prefer the pheromones of sexually developed males over the host fruit odor. Females exhibit this preference until mating occurs, following which they prefer the host fruit odor.[16] This finding has been evidenced by a specific protein, CcapObp22, that shows approximately 37% identity with the pheromone binding protein of Drosophila melanogaster. In a recent study, this protein was shown to bind male pheromone components, specifically farnesene, a highly strong hydrophobic terpene.[17]
Sex determination in C. capitata is by the typical XY system.[18] Unusually for a dipteran and for a frugivore, medflies do not have an opsin gene for blue light perception as shown from the whole-genome sequencing project completed in September 2016.[19] In a study done by Spanos et al. in 2001, researchers were able to sequence the entire mitochondrial genome of the fly. They found that the genome was 15,980 base pairs long with 22 tRNA genes and 13 genes encoding mitochondrial proteins. Using this information, researchers were able to use this genome sequence as a diagnostic tool for population analysis and a method to determine the source of recent introductions.[20]
In a 1987 study completed by Postlethwait et al., researchers assessed the immune response of the medfly using bacterial inoculation. After inoculating the medfly with Enerobacter cloacae, the researcher extracted the haemolymph from the males and found that it contained potent antibacterial factors compared to the haemolymph of controls. Through further testing, they were able to show that these potent factors were generated within 3 hours of inoculation and lasted for approximately 8 days. This finding indicated that medflies do have an adaptive immune response that is similar to the Drosophila melanogaster.[21]
Since it has been established that C. capitata is a cosmopolitan pest that affects hundreds of commercial and wild fruit species, considerable research has been done to assess the medfly's ability to transmit diseases. A 2005 study conducted by Sela et al. utilized green fluorescent protein (GFP)-tagged E. coli placed in fruit fly feeding solution to show that flies inoculated with GFP-tagged E. Coli was able to harbor the bacteria for up to 7 days following contamination. This finding showed that the medfly has the potential to be a vector of human pathogens to fruits.[22]
Studies have shown that wild C. capitata flies were found to partake in more head-butting behavior, direct opponent contact, and less likely to cede an occupied leaf to an invader. Furthermore, it was found that sounds that are produced during body vibration constitutes threat behavior. Aggressive sounds are substantially higher in pitch (roughly around 1–3 kHz) while sounds produced during non-aggressive moments such as courtship times tended to be around 0.16-0.35 kHz.[23] Aggressive behaviors can be observed during the courtship ritual. If the approaching fly is discerned to be an intruder male fly, the resident male fly terminates his calling position and lunges towards the intruder, physically pushing the intruder with his head. This interaction lasts until either party loses position or eventually leaves the position. Males can also partake in passive defensive actions which consists of a “face-off” with the intruder male rather than a physical “head-butt”. Males in the “face-off” position can last up to 5 minutes until one male eventually turns and leaves the territory.[13]
In the United States, C. capitata has invaded four states (Hawaii, California, Texas, and Florida) but has been eradicated from all but Hawaii. However, reintroduced populations of the medfly have been spotted in California as recently as 2009, requiring additional eradication and quarantine efforts.[24] It has also been eradicated from New Zealand and Chile.
Medflies were first detected in the region in Costa Rica in 1955. From then on, the medfly spread northward, reaching Guatemala in 1976 and Mexico in 1977. In order to begin eradication efforts, the Mass-rearing and Sterilization Laboratory was producing 500 million sterile flies weekly by the end of 1979. By releasing these sterile flies into the wild, scientists were able to not only prevent the northward spread of the fly, but officially declare it as eradicated from all of Mexico and large areas in Northern Guatemala in September 1982.[25]
Utilizing the Sterile Insect Technique, the medfly was eradicated in December 1984 from Carnarvon, Western Australia. In the 1980s, the Western Australia Department of Agriculture conducted a feasibility study into using the Sterile Insect Technique to eradicate the medfly population. Phase 1 of this study utilized 70 traps to establish the seasonal abundance of wild fly prior to releases. In Phase 2 of the study, the Department of Agriculture released 7.5 million sterile flies per week; however, this was insufficient in limiting the wild fly population. During phases 3 and 4, the number of released sterile flies increased to 12 million a week and was combined with chemical controls. After wild flies were no longer detected, phase 5 was initiated, withdrawing chemical controls from further distribution. Eradication was declared when neither wild flies nor larvae were found during the period of October 1984 to January 1985. This period corresponded to 3 fly generations; a threshold of eradication utilized by Hendrichs et al. (1982) in the eradication of the medfly in Mexico.[26]
Much research has been dedicated to means of controlling the medfly.[27] In particular, use of the sterile insect technique has allowed the species to be eradicated from several areas.
In 1981, California Governor Jerry Brown, who had established a reputation as a strong environmentalist, was confronted with a serious medfly infestation in the San Francisco Bay Area. He was advised by the state's agricultural industry and the US Department of Agriculture's Animal and Plant Health Inspection service (APHIS) to authorize airborne spraying of the region. Initially, in accordance with his environmental protection stance, he chose to authorize ground-level spraying only. Unfortunately, the infestation spread as the medfly reproductive cycle outpaced the spraying. After more than a month, millions of dollars of crops had been destroyed and billions of dollars more were threatened. Governor Brown then authorized a massive response to the infestation. Fleets of helicopters sprayed malathion at night, and the California National Guard set up highway checkpoints and collected many tons of local fruit. In the final stage of the campaign, entomologists released millions of sterile male medflies in an attempt to disrupt the insects' reproductive cycle.
Ultimately, the infestation was eradicated, but both the governor's delay and the scale of the action has remained controversial ever since. Some people claimed that malathion was toxic to humans, animals, as well as insects. In response to such concerns, Brown's chief of staff, B. T. Collins, staged a news conference during which he publicly drank a small glass of malathion. Many people complained that, while the malathion may not have been very toxic to humans, the aerosol spray containing it was corrosive to car paint.[28]
During the week of September 9, 2007, adult flies and their larvae were found in Dixon, California. The California Department of Food and Agriculture and cooperating county and federal agricultural officials started eradication and quarantine efforts in the area. Eradication was declared on August 8, 2008, when no "wild" (i.e. non-sterile) medflies were detected for three generations.
On November 14, 2008, four adult flies were found in El Cajon, California. The San Diego County Agricultural Commission implemented a treatment plan, including distributing millions of sterile male flies, local produce quarantines, and ground spraying with organic pesticides.[29]
Ceratitis capitata, commonly known as the Mediterranean fruit fly or medfly, is a yellow-and-brown fly native to sub-Saharan Africa. It has no near relatives in the Western Hemisphere and is considered to be one of the most destructive fruit pests in the world. There have been occasional medfly infestations in California, Florida, and Texas that require extensive eradication efforts to prevent the fly from establishing itself in the United States.
C. capitata is the most economically important fruit fly species because of both its ability to survive cooler climates more successfully than most other fly species and its ability to inhabit more than 200 tropical fruits and vegetables to which it causes severe destruction and degradation. The practices that are used to eradicate the medfly after its introduction into a new environment can be extremely difficult and expensive, but infestation of C. capitata lowers crop yields and induces costly sorting processes for fresh fruits and vegetables.
