The Mediterranean fruit fly or medfly, (Ceratitis capitata Wiedemann, 1824), is an insect belonging to the Tephritidae family.
From a systematic point of view it belongs to:
C. capitata species.
The following terms are synonymous:
– Ceratitis citripeda Efflatoun, 1924;
– Ceratitis citriperda Macleay, 1829;
– Ceratitis hispanica Breme, 1842;
– Pardalaspis asparagus Bezzi, 1924;
– Tephritis capitata Wiedemann, 1824;
– Trypeta capitata (Wiedemann, 1824).
Geographic Distribution and Habitat –
Ceratitis capitata is a phytophagous insect whose larva develops as carpophagus and polyphagous within the pulp of many fruits.
It is an insect of probable origin from sub-Saharan Africa or West Africa, from which it settled in the Mediterranean basin over a century and then spread throughout the world. Currently it is in fact a cosmopolitan species, present all year round in the tropical and subtropical regions of all continents: North America, South America, Asia, Oceania. On the other hand, in temperate zones its presence is seasonal. It is also present in the southern United States (California, Texas, Florida) and in Mexico, where it disappeared in North America in the 1980s, only to reappear on several occasions in California.
Instead, it disappeared in New Zealand and Hawaii.
This fly is polyphagous and lives mainly on plants such as stone fruit, pome fruit, citrus fruit, kaki, fig, actinidia, etc.
Ceratisis capitata is a small 4-6 mm long fly.
It has a garment characterized by two greenish compound eyes.
The thorax is yellowish-gray in color.
The membranous wings and have characteristic ocher yellow spots.
The abdomen, rounded and pointed at the end, is yellow-orange in color, with silvery gray transverse stripes.
The larvae are whitish, carpophagous and specifically adapted to endophytic life.
The larvae are apod, elongated, sub-conical, narrow towards the head, of a white-yellowish color. The newborn larvae are less than a millimeter long and are difficult to perceive with the naked eye. The mature ones are 7-9 mm long.
The pupae derive from the moult of mature larvae and are protected inside the puparium by an elliptical capsule formed by a transformation of the exuvia of the last larval moult, of a reddish color. The puparium is 4-5 mm long. In some strains the pupari from which the females will flicker are white, those from which the males will flicker are reddish-brown.
The eggs are elongated and slightly curved and measure about 1.0 x 0.2 mm; they are bright white in color, with a protruding micro-pile area.
Attitude and Life Cycle –
In mild winter regions, Ceratisis capitata overwinters mainly at the pupal stage in the ground, a few centimeters deep. In citrus-growing areas, it also winters as an adult or as a larva in citrus fruits. Temperatures below 2 ° C for a week result in the death of the pupae. In tropical regions, generations follow one another uninterruptedly throughout the year.
In Italy the flicker of adults occurs in the month of May-June.
The female lays the eggs preferably on fruits with a high content in sugars, with a low degree of acidity and with a tender pulp. This preference means that the attacks depend on the type of fruit and the season. In southern Italy, in the height of summer, the attacks preferably target peach trees, apricots, figs and early pear varieties, while plum trees are generally avoided. In late summer the attacks also extend to other varieties of pear, apple, sometimes plum and grape, but especially prickly pear and early varieties of persimmon. In autumn the attacks continue on prickly pears and persimmon to finally move on to citrus fruits, in particular clementines and early oranges from the Navel group (Naveline).
The female, usually 4-6 eggs are laid per puncture, up to a maximum of ten. A female can also practice several stings on the same fruit, so you can also lay several dozen eggs in a single fruit. Over the course of her life, a female can lay a few hundred to a thousand eggs, so she can attack hundreds of fruits.
The first generation, resulting from the first oviposition, can be followed by 5-6 during the year; the first generations develop on the stone fruit, then, the insect passes on the pome fruit and, in the south, on the citrus fruit in the late summer-autumn generations.
These last generations are those that involve the highest density of the pest population.
In general, Ceratisis capitata also completes 6-7 generations a year, in central-southern Italy and 3-4 generations in the northern one.
The duration of the development cycle, from egg deposition to flickering, depends on the temperature and varies from a minimum of 2 weeks (at 29 ° C in the laboratory) to a maximum of 3 months (10-12 ° C). Under ordinary conditions, the duration of a summer generation is of the order of 20-30 days. Below 9 ° C biological activity stops completely.
Immediately after exiting the egg, the larvae develop inside the pulp causing it to decay. When ripe, they come out of the fruit, drop and pupate in the ground. Contrary to the olive fly, the pupa stage always takes place outside the attached fruit.
The population dynamics of this insect varies according to the geographic region and according to the years.
The dynamics are determined by three conditions: the seasonal thermal course, with particular reference to the cold season, food availability, the reproductive potential of the species. Since the biological potential increases from generation to generation, the danger of the species depends on the number of generations that are repeated over the course of the year and on the speed with which the first generation develops. For this reason the danger of the species is closely linked to the latitude.
Ecological Role –
The Mediterranean fruit fly is one of the most economically significant adversities affecting summer fruit produced in the Mediterranean environment.
This polyphagous insect affects over 250 agricultural species.
In Italy it is particularly harmful on some stone fruit (peach and apricot), on the fig, on the prickly pear and on the persimmon. In years of serious infestations, attacks also affect pome fruit (apple, pear, Japanese medlar), strawberry, kiwi. On citrus fruits, the attacks have generally proved to be of lesser severity than other fruit trees, thanks to the inhibiting action exerted by the essential oil contained in the flavedo, but in recent years the damage has become more severe, probably due to a greater diffusion of types genetics with longer ovipositor, able to lay eggs deeper. In any case, citrus fruits are the fundamental guests for late generations in the countries of the Mediterranean basin.
Damage occurs on the fruit and is caused by:
– from oviposition punctures that determine the appearance of zoned and soggy areas (Citrus fruits) subject, subsequently, to rot;
– from the activity of the larvae that develop in a gregarious way inside the fruits; they feed on the pulp also causing the soft decay of the pulp itself which is subsequently also attacked by fungal rot agents, determining the complete degeneration of the fruit.
Affected fruits are subject to drop.
The fight against Ceratitis capitata is constantly evolving and, like other insects, it will be significantly affected by the application of agro-ecological techniques towards a lesser specialization of tree plants and more resistant species.
Until a few years ago, the fight against fruit fly was of a chemical type, with criteria of guided and integrated fight; some biotechnological means are currently being tested which have shown some success in controlling the populations of Ceratisis capitata.
Before intervening in the fight, however, it is advisable to carry out monitoring to establish the useful intervention threshold.
In general, the methods of fighting Ceratitis capitata are the following:
– guided and integrated chemical fight;
– biological fight;
– biotechnical struggle.
The chemical and integrated fight requires the use of active ingredients with cytotropic action, able to penetrate the fruit and carry out their preventive or curative action against the newborn larvae. The larvicidal treatment of larvae that have already started development is of no use as the damage has already occurred.
The calendar fight, used above all in the past, provides for the protection of the fruits by repeating the treatment near the end of the shortage interval. This approach is not very effective and has a significant environmental and economic impact.
In fact, the impossibility of identifying infestations in the bud forces to start treatments well in advance with a consequent increase in the number of interventions.
Ultimately, the calendar fight involves a significant increase in costs, a greater impact on the useful entomofauna due to the use of broad spectrum insecticides, a greater risk to the health of consumers, negative aspects that are not counterbalanced by a adequate effectiveness.
A step forward in defense of nature took place with the guided struggle which is a more rational approach, it being understood that the suspension of treatments near the harvest does not guarantee the safety of the production. Due to the impossibility of identifying the beginning of the infestations, the guided fight can only be practiced with the monitoring of adults, using chromotropic traps or, better, traps triggered with chemical attractants. Given the remarkable biological potential of this species, the intervention threshold is very low.
In the chemical fight it is performed with principles of cytotropic activity towards both larvae and adults.
The adulticide treatment can also be performed with the use of poisoned protein baits. This carried out on large surfaces has always offered better results than larvicidal treatments. In this case, localized spraying (for example in alternating rows on part of the canopy) of products based on hydrolyzed proteins and an insecticide (phosphoric ester or pyrethroid) is used. Adults are attracted to the food attractant and are killed before reproduction.
It should be emphasized, however, that the fight with the bait is effective if carried out on large surfaces and very early, at the appearance of the first adults (the intervention thresholds range according to the context from minimum values from 1 to 3-4 adults up to a maximum of 20-40 adults per trap per week in conditions favorable to the proliferation of the phytophagous). The containment of the oviposition of the first generation allows to keep the level of infestations low.
The biological fight has not, to date, been very successful. This fly, despite having several natural antagonists, has a very high biological potential and only in particular contexts can the auxiliaries exercise an effective control action. Among these is mentioned in the reading the biological control in the Hawaiian Islands for several decades with Opius species introduced by Filippo Silvestri in 1913.
Biological control will be more successful with the biodiversification of crops within farms and districts but in conditions of crop specialization it is practically not very applicable.
Furthermore, in the Mediterranean basin there is no real auxiliary antagonist that can play a significant role in biological control. Some microorganisms and some occasional predators contribute to the containment of populations. Among the parasitoids, the action of Opius concolor (Hymenoptera Braconidae) and Pachyneuron vindemmiae (Hymenoptera Pteromalidae) in North Africa and the Middle East has been reported. The first species has also been used in biological control programs.
In recent times the biotechnological fight is coming to the rescue to contain Ceratitis capiata.
This fighting technique is that of autocide, based on the breeding of large quantities of insects that are sterilized in laboratories and then released into the environment.
This operation must be repeated several times taking into account that a competition of at least 1: 1, i.e. a sterile insect thrown into the environment and a fertile insect, reduces the reproductive potential of the species by 50% (a 9: 1 ratio reduces it to 10 %).
Sterilization is done by radiation or with chemosterilizing substances.
In any case, the success of the technique is directly proportional to the size of the surface affected by the intervention, the density of the initial population, the number of insects launched and the competitiveness of sterile males compared to fertile ones.
In conclusion, it must be said that the agroecological approach is the real and only solution to the containment of this insect. However, this approach requires the intervention to start in the planning phase of the crops, avoiding too dense sixths, excessive specialization of the plots or production areas, introduction of associations, grassing and techniques that allow the establishment of the parasites of this insect and so on. .
The proliferation of many insects, as in the case of Ceratitis capitata, occurs because the conditions of the agroecosystem are very far from those of ecological balance to which the insect somehow reacts.
– Wikipedia, the free encyclopedia.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.