CERATITIS CAPITATA: CHARACTERISTICS, BIOLOGICAL CYCLE AND CONTROL - BIOLOGY - 2024

Ceratitis capitata is the scientific name of the commonly called Mediterranean fruit fly. It is a dipteran insect that, having originated on the west coast of Africa, has managed to spread to many other regions of tropical and subtropical climates on the planet, considered an invasive species and plague.

The fruit fly is considered a cosmopolitan species due to its wide dispersal throughout the world. The most probable cause of this phenomenon is the increase in the international commercial exchange of fruits, which can transport to enormous distances and in a short time the fruits infected with the eggs that the females could have deposited inside.

Figure 1. Ceratitis capitata, Mediterranean fruit fly. Source: Jari Segreto, via Wikimedia Commons

Within the order Diptera there are several species also commonly known as "fruit flies", which cause serious damage to fruit crops and their crops. For example, these fruit flies include the olive fly (Dacus oleae) and the cherry fly (Rhagoletis cerasi).

Ceratitis capitata is the most aggressive species from the point of view of the diversification of its diet of various fruits, and it is also the one with the largest worldwide distribution; For this reason it is the one that causes the greatest problems in their crops.

characteristics

Adult

The fruit fly is slightly smaller in size than the house fly; 4 to 5 mm. The body is yellowish, the wings are transparent, iridescent, with black, yellow and brown spots.

The thorax is whitish-gray in color, with black spots and has a mosaic of characteristic black spots and long hairs. The abdomen has two lighter bands in a transverse direction. The female has a conical abdomen.

The scutellum is shiny, black, and the legs are yellowish. The eyes are red and large. The male is slightly smaller and has two long hairs on its forehead.

Egg

The egg is ovoid in shape, pearly white when freshly laid, and yellowish afterwards. It is 1mm x 0.20mm in size.

Larva

The larva is creamy-white in color, elongated, similar to a worm. It has no legs and is 6 to 9 mm x 2 mm in size.

Pupa

The pupa is the intermediate stage of metamorphosis between the last larval stage and the adult or imago stage. After the last larval molt has finished, a brownish covering appears inside which a stage develops that undergoes many changes until it reaches the adult stage. The puparium or envelope is broken and the adult emerges.

Biological cycle

Passage from pupa to adult

The imago or adult emerges from the puparium (buried in the vicinity of trees) towards a place with solar lighting. After approximately 15 minutes, the adult acquires its characteristic colors.

Subsequently, the imago makes short flights and searches for sugary substances (which it needs for its full sexual development) in fruits, flower nectaries and exudations of other insects such as mealybugs and aphids.

Egg copulation and laying

The well-developed male secretes an odorous substance that acts as an attractor for the female, and copulation occurs. The fertilized female rests on the fruit, moves in circles, explores, pierces the epicarp and lays the eggs inside the fruit. The operation can take up to half an hour.

Surrounding the wound in the fruit, pale spots appear when the fruit is still green and brown when it is ripe, indicating infection of the fruit. The number of eggs deposited within the chamber dug in the fruit varies between 1 to 8.

Egg hatching: larva stage

After about 2 to 4 days, depending on the season of the year, the eggs hatch inside the fruit. The larvae, which are provided with jaws, burrow galleries through the pulp into the fruit. Under favorable conditions, the larval stage can last from 11 to 13 days.

Larval to pupal transition

The mature larvae have the ability to leave the fruit, fall to the ground, jump into an arched shape, disperse and burrow several centimeters deep to transform into a pupa. The transformation into an adult mosquito occurs between 9 to 12 days.

The biological cycle of Ceratitis capitata experiences variations depending on the climate; the plant attacked and the degree of infection varies from place to place.

Species it attacks

The fruit fly Ceratitis capitata can attack a huge variety of fruits, such as oranges, tangerines, apricots, peaches, pears, figs, grapes, plums, medlars, apples, pomegranates, and practically all fruits grown in tropical and subtropical areas, such as avocado, guava, mango, papaya, date or custard apple.

If conditions of accelerated growth rates and overcrowding occur, the fly can infect other plants that are available, such as tomatoes, peppers, and various species of legumes.

Biologic control

Control methods for the Ceratitis capitata fly must be aimed at attacking all its stages, from the reproductive adult to the fruit miner larvae and the pupae buried under the ground.

Complementary general methods

Manual techniques

In the first place, the daily manual harvesting of the infected fruits in the crop is very important, their deposit in pits with enough lime and the subsequent spraying of the removed soil with some biological insecticide, such as aqueous extract of basil, for example. Infected fruits must be removed immediately and placed in closed bags.

Flycatcher and flycatcher traps

The use of flycatchers and fly traps is also recommended. To implement this method, special jars are placed in the fruit trees, which contain attracting substances for the fly, which are trapped inside and die there.

Baits

As attractor substances or baits vinegar, ammonium phosphate solution, hydrolyzed protein solution, among others are used. Sex attractors are also used, such as Trimedlure, which only selectively attract males, decreasing their number within the population and resulting in a decrease in the growth rate.

Chromotropic traps

Additionally, chromotropic traps have been used, which are designed with the most attractive colors for the fly; generally a range of yellows.

Figure 2. Chromotropic trap to catch Ceratitis capitata made with PET bottle. Source: Morini33 via es.m.wikipedia.org

Self-acid biological control

The method of biological control in the strict sense that has been tried is the use of sterile males. This is called autocidal, because in this case the population controls itself.

This technique was initially developed in the United States of America and has been in use for more than 60 years. It is a method approved and recommended by the Program for Nuclear Techniques in Food and Agriculture of the FAO-United Nations (Food and Agriculture Organization).

In Spain, it has been developed at the National Institute of Agrarian Research, El Encín farm, near Madrid.

What is self-acid biological control?

Autocidal control consists of the mass rearing of adult male individuals that are sterile. These, when released in large numbers within active populations, compete successfully with fertile individuals and mate with females, to produce a considerable reduction in the number of new adults. In this way the size of the fly population can be reduced until it is exterminated.

Conditions required for successful autocidal biological control

The conditions required for the successful achievement of this type of self-acid biological control are the following:

1. Achievement of mass rearing of sterile males morphologically identical to fertile males.
2. Successful introduction of a significant number of sterile males into the natural working population of fruit flies and achieve their homogeneous distribution.
3. The ideal time for the massive introduction of sterile males is the time when the natural population has experienced a greater decline.
4. The area of ​​the insertion of sterile males must be protected from new invasions of the Ceratitis capitata fruit flies.

Mass rearing of males

The massive rearing of males is carried out artificially in special hatcheries. In the past, sterilization was carried out at the stage of the biological cycle in which the so-called "red eyes" appear, visible through the pupal envelope, at which time the germ cells of the gonads are formed. This produced sterile males and females.

Sterile females are not suitable because they maintain their ability to lay eggs in fruits. These eggs are not fertile, but their laying begins with a perforation of the fruit through which bacteria and fungi penetrate.

Currently, genetic engineering techniques produce females with a white puparium and males with a normal, brown puparium. The female pupae are removed with the use of a separator equipped with a photoelectric cell and then only the male pupae are sterilized.

Sterilization

Sterilization can be achieved through physical or chemical methods.

Physical methods of sterilization

The physical method used to sterilize artificially reared males is exposure to ionizing radiation from radioactive isotopes. Radioactive cobalt ganma rays are generally used.

At this stage, the radiation dose requires rigorous control; Excessive exposure to high-energy radiation, which could cause damage to morphology, must be prevented. These damages could result in unfavorable competition with fertile natural males for females, and failure of the method.

Chemical sterilization methods

Sterilization through chemical methods consists of subjecting artificially reared males to the ingestion of some substances that cause their sterility. This method is less used.

Advantages of the self-acid method

1. It is a specific method with effects restricted to the damaging species, without effects on other insects or on other living beings in the ecosystem.
2. The technique does not produce environmental pollution.
3. It is a very efficient technique.

References

1. Papanicolaou, A., Schetelig, M., Arensburger, P., Atkinson, PW, Benoit, JB et al. (2016). The whole genome sequence of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), reveals insights into the biology and adaptive evolution of a highly invasive pest species. Genome Biology. 17:192. doi: 10.1186 / s13059-016-1049-2
2. Sosa, A., Costa, M., Salvatore, A., Bardon, A., Borkosky, S., et al. (2017). Insecticidal effects of eudesmanes from Pluchea sagittalis (Asteraceae) on Spodoptera frugiperda and Ceratitis capitate. International Journal of Environment, Agriculture and Biotechnology. 2 (1): 361-369. doi: 10.22161 / ijeab / 2.1.45
3. Suárez, L., Buonocore, MJ, Biancheri, F., Rull, J., Ovruski, S., De los Ríos, C., Escobar, J. and Schliserman, P. (2019) An egg-laying device to estimate the induction of sterility in Ceratitis capitata (Diptera: Tephritidae) sterile insect technique programs. Journal of Applied Entomology. 143 (1-2): 144-145. doi: 10.1111 / jen.12570
4. Sutton, E., Yu, Y., Shimeld, S., White-Cooper, H. and Alphey, L. (2016). Identification of genes for engineering the male germline of Aedes aegypti and Ceratitis capitata. BMC Genomics. 17: 948. doi: 10.1186 / s12864-016-3280-3
5. Weldon, CW, Nyamukondiwa, C., Karsten, M., Chown, SL and Terblanche, JS (2018). Geographic variation and plasticity in climate stress resistance among southern African populations of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Nature. Scientific Reports. 8: 9849. doi: 10.1038 / s41598-018-28259-3