The Mediterranean fruit fly, Ceratitis capitata

Savvas Pastopoulos, Agronomist MSc, Pastopoulos Agronomics, Neos Mylotopos, Pella, Greece

The Mediterranean fruit fly, Ceratitis capitata, is among the most important insect pests of fruit growing in many parts of the world. It attacks half-ripe and ripe fruit, which is destroyed. In northern Greece it is not a pest that strikes with the same intensity every year, and the reason for that swing is one of the more interesting chapters in the biology of the insect.

>350hosts
in 70 plant
families

32 daysfull life cycle
at 25 °C

100%pupal mortality
over winter in
northern Greece

400–700 mthe distance
90% of individuals
move

Contents

Identity and host range
How it is recognised
The life cycle
How many generations it completes
How it overwinters in northern Greece
The damage to the fruit
Monitoring with traps
How far it travels
Control, the three tools
The resistance question
The picture in the Giannitsa area
Sources

1. Identity and host range

The insect originates in sub-Saharan Africa and spread from there first to the Mediterranean and then to Latin America, Australia and Hawaii. In Europe it is established mainly in the Mediterranean zone and is listed on the EPPO A2 list, that is, on the list of organisms already present in the EPPO region for which the Organization recommends regulation to its member countries. The EPPO list is a recommendation and not law: quarantine status in the Union is set by Regulation (EU) 2019/2072. In Greece the insect is established and is handled as a common pest of the crop, not as a quarantine organism.

Its polyphagy is among the broadest found in any insect pest. It is recorded on more than 350 confirmed hosts worldwide, belonging to 70 plant families, and the list keeps growing. Among them are practically all the crops of interest here:

Stone fruit, sweet cherry, apricot, plum, peach, almond
Pome fruit, apple, pear, quince, loquat
Citrus, all species
Persimmon, fig, pomegranate, kiwifruit, walnut, olive, grapevine

Why the host list matters Because the insect is polyphagous, it uses whatever hosts the surrounding landscape offers as stepping stones. The crop in question does not have to be continuously available for the population to persist. A fig tree in a yard, a neglected loquat, a few trees on an abandoned holding are enough to bridge the gap until the commercial fruit ripens. A clean orchard does not mean a clean district.

2. How it is recognised

The adult, the fly

Smaller than the house fly, about 4 to 6 mm long.
Its colouring is distinctive: it carries black, brown and yellow markings on the thorax.
The wings are transparent and carry transverse brown, yellow and black bands. This is the most reliable feature visible without a microscope.
The female is told by the ovipositor at the tip of the abdomen, with which it pierces the fruit skin.

Adult Mediterranean fruit fly on a persimmon fruit — An adult Mediterranean fruit fly on a persimmon fruit. All three features described above are visible: the **transverse brown and yellow bands on the wings**, which are the most reliable feature without a microscope, the **thorax with its black and silver markings**, and the **iridescent eyes**. The size of 4 to 6 mm can be judged against the surface of the fruit.

The larva, the "maggot"

Headless, with no distinct head capsule.
Narrow at the front and cylindrical behind, the anterior end slightly curved downward and the posterior end flattened.
It reaches 9 mm in length.
It carries mouth hooks with which it tunnels through the flesh.

A caution: identification to species is not possible from the larva. Where certainty is needed, the larvae must be reared through to the adult stage.

3. The life cycle

Step by step

After emergence the adults feed on substances such as nectar or insect honeydew. That feeding is essential for the eggs to mature.
Within 3 to 6 days of emergence the females are ready to reproduce, and once they have mated their destructive work begins.
The female pierces the skin and lays the eggs beneath it. She usually lays 1 to 6 eggs per oviposition puncture, while in large fruit the number per puncture can be considerably higher.
After hatching, the larvae develop at the expense of the ripe fruit, side by side. They pass through three larval instars inside the fruit.
The mature larva leaves the fruit, enters the soil and pupates there, inside a hard puparium.
The new adult emerges from the puparium.

The durations that follow come from rearing at constant laboratory temperatures and show the extent of the temperature effect, not field durations.

Stage	Duration
Larval	5 days at 30 °C to 21 days at 15 °C
Pupal	8 days at 30 °C to 35 days at 15 °C
Full cycle	about 32 days at 25 °C
Adult lifespan	on average 11 weeks for males, 9 weeks for females

Temperature does not merely speed the cycle up, it multiplies it The difference is worth looking at: at 30 °C the insect completes the larval and pupal stages in 13 days; at 15 °C it needs 56 days. Four times as long. That is exactly why a warm, drawn-out September can add a whole generation onto ripe fruit, and why monitoring does not stop when the first cool weather arrives.

4. How many generations it completes

In Greece it reaches as many as 7 generations a year in the warmest districts of the south. The number is not fixed, however: it depends on temperature, host availability and the local bioclimate.

In the Giannitsa area my own reading is that it completes 2 generations, according to the weather of the season. The constraint is not food, hosts are abundant. The constraint is the winter, and that is explained in the next chapter.

5. How it overwinters in northern Greece

This is the key to understanding why the insect behaves so differently in Macedonia from the way it behaves in Crete or in the Peloponnese. And the answer is not conjecture: it has been studied over three consecutive winters in an orchard in northern Greece, at the northern limit of the insect's establishment.

What the research showed

Larvae inside naturally infested fruit, pupae and adults were exposed to natural temperature conditions in late autumn and early winter. The results:

100% mortality for pupae and for adults. No survival at all.
Mortality above 60% for the larvae, but not complete.
Those larvae that did survive suffered high mortality at the following, pupal stage as well. And a clear rule held: the earlier they left the fruit during winter and spring, the lower their survival.
Females that emerged between March and May laid fertile eggs in late spring and early summer. Mean adult lifespan was about 90 days and mean fecundity 247 eggs per female.

From this it follows that in northern Greece the population does not overwinter as a pupa in the soil, there it dies out completely. What overwinters is a proportion of the larvae, inside infested fruit, prolonging their larval development; and it is that proportion which regenerates the population the following spring.

Why some years "have no medfly" The explanation for something seen in the field follows directly from the above: after a winter with severe frosts there have been seasons with not a single catch until the middle of September.

The interpretation is now obvious. The following year's population hangs by a thread: the few larvae that manage to survive inside fruit left on the tree or on the ground. A hard winter cuts that thread too, and the season starts effectively from zero. Conversely, a mild winter means an early and dense first flight.

And the practical consequence that is not obvious If the population survives inside the fruit that is left behind, then collecting and destroying infested and fallen fruit is the cheapest and most powerful control measure available in northern Greece. An orchard that is cleaned thoroughly after harvest starts the following season under far lower pressure. The fruit is not tipped at the edge of the field; it is buried deep or taken away.

6. The damage to the fruit

Infested fruit carries minute oviposition punctures which, like the other symptoms, are often hard to find in the early stages. Substantial damage may already have been done inside the fruit before anything shows on the outside, in the form of a network of tunnels accompanied by rot.

The fruit is then colonised by fungi and rots. The damage is therefore not only the larva: it is the entry point that the puncture opens.

Infested persimmon fruit, oviposition puncture and rot — An infested persimmon fruit. The **oviposition puncture** shows as a dark sunken point, and around it the flesh has softened and discoloured. The picture shows why the puncture on its own is the smaller part of the problem: **the whole fruit is lost, not the area of the hole**. On the upper side a second, much smaller dark speck is visible, at the stage where the infestation still passes unnoticed on the grading line.

7. Monitoring with traps

Without monitoring there is no correct timing, and without timing every intervention is a matter of luck. There are two different trapping logics and they do not do the same job:

Type of lure	What it catches	What it is good for
Parapheromone (trimedlure) or ginger root oil	Only the males	Early detection of the start of flight. Sensitive and clean to read.
Protein lures (food based)	Both sexes	Estimating the real size of the population and the proportion of females, which are the ones that do the damage.

In the Giannitsa area, on the trapping system I run, the start of the first flight is normally detected between 15 August and 5 September.

Why protein lures work This is not an arbitrary choice. Both sexes are strongly attracted to a protein source that releases ammonia. The flies need protein for their eggs to mature, and that physiological need is exactly the same weak point on which bait sprays rely.

8. How far it travels

Mark and recapture experiments found that 90% of individuals move only 400 to 700 metres, and that a new focus is as a rule contained within a radius of 1 kilometre of the point of entry. Only a very small proportion disperses beyond 10 kilometres.

Two conclusions from one number

The first is encouraging. The population that matters to any given orchard is overwhelmingly local. What that orchard and its immediate neighbours do counts for something real. A coordinated effort across a neighbourhood of holdings has a measurable effect.

The second is a warning. The main route into new areas is not flight, it is the movement of infested fruit. The insect travels in crates, not on its wings.

9. Control, the three tools

Control of the insect in central and southern Greece is particularly difficult. It demands continuous monitoring of the population and careful synchronisation of the control measures. There are three tools:

1. Bait sprays

These combine a protein lure with an insecticide. Their advantage over cover sprays is substantial: they are applied as a spot treatment on patches, the flies are drawn to the insecticide, and the effect on beneficials and natural enemies is minimal. In the Mediterranean the active substance that has come to dominate baits is spinosad.

2. Cover sprays

These cover the whole canopy and target the adults arriving at the fruit. They are the most drastic tool but also the most burdensome, with the greatest effect on beneficial insects and the strictest pre-harvest intervals, a critical point, since these are applications onto ripe fruit shortly before harvest.

3. Mass trapping

A dense network of lure traps, to bring the population down directly. It has been proposed that bait stations, devices combining lure and insecticide in a fixed position, are as effective as bait sprays and cheaper. The measure performs better when it is applied across a district rather than on a single holding.

The agronomist on the ground judges which of the three is appropriate, on the basis of the crop, the stage of the fruit, the size of the population and the pre-harvest intervals.

What has changed in the armoury

Dimethoate, the organophosphate on which fruit fly control rested for decades, is no longer approved in the European Union. Non-renewal was decided by Commission Implementing Regulation (EU) 2019/1090, and member states were required to withdraw authorisations for the relevant products by 17 January 2020.

The reason was that, according to EFSA, a risk from exposure to residues of dimethoate, whose genotoxic potential could not be ruled out, and of its main metabolite omethoate, which was considered mutagenic in vivo, could not be excluded. The gap it left is filled today mainly by spinosad baits and by mass trapping.

10. The resistance question

A small armoury creates the familiar problem: when few active substances are used continuously and on a large scale, the population adapts.

What has already been recorded In field populations, resistance to lambda-cyhalothrin has been documented and resistance alleles for spinosad have been detected. The susceptibility of Greek populations to deltamethrin and to spinosad has been examined specifically.

The practical consequence: the non-chemical measures, orchard sanitation, mass trapping, correct timing based on the traps, are not supplementary. They are what keeps the few available active substances working.

11. The picture in the Giannitsa area

The local picture, in brief

Which crops are at risk. Around Giannitsa the insect threatens mainly persimmon and some late plum cultivars. The reason is timing: these are the fruits that ripen exactly when the population reaches its peak.
When flight starts. Normally between 15 August and 5 September.
How many generations. About 2, according to the weather of the season.
What decides the season. The preceding winter. Severe frosts mean a late and sparse flight; a mild winter means an early and dense one.
What comes first. Traps from mid-August, and thorough removal of infested and fallen fruit after harvest.

12. Sources

EPPO (2021). Datasheet: Ceratitis capitata. EPPO Global Database. Source for the >350 hosts in 70 families, the A2 listing, the life cycle and pupation in the soil, the stage durations at 15–30 °C, adult lifespan, the lures and the rationale of bait sprays.
Papadopoulos, N.T., Carey, J.R., Katsoyannos, B.I. and Kouloussis, N.A. (1996). Overwintering of the Mediterranean Fruit Fly (Diptera: Tephritidae) in Northern Greece. Annals of the Entomological Society of America 89(4):526–534. The key study for this region. Three winters in an orchard in northern Greece, at 40.3°N. Source for the 100% mortality of pupae and adults, the >60% mortality of larvae, the relationship between survival and the timing of exit from the fruit, and the 90-day adults with 247 eggs per female.
Commission Implementing Regulation (EU) 2019/1090 of 26 June 2019, concerning the non-renewal of approval of the active substance dimethoate. Source for the withdrawal and for the deadline of 17 January 2020 for revoking authorisations.
Kakani, E.G. et al. (2018). Susceptibility of Ceratitis capitata to deltamethrin and spinosad in Greece. Journal of Pest Science 91:1015–1023. Source for resistance to lambda-cyhalothrin and for spinosad resistance alleles in field populations.
Toxicity of spinosad in protein bait to three economically important tephritid fruit fly species and their parasitoids. Journal of Economic Entomology (2004). Documentation of spinosad as a bait active substance.
Meats, A. and Smallridge, C.J. (2007). Short- and long-range dispersal of medfly, Ceratitis capitata, and its invasive potential. Journal of Applied Entomology 131:518–523. Source for 90% of individuals moving 400–700 m.
Piñero, J.C., Enkerlin, W. and Epsky, N.D. (2014). Recent developments and applications of bait stations for integrated pest management of tephritid fruit flies. In Trapping and the Detection, Control, and Regulation of Tephritid Fruit Flies, Springer, pp. 457–492. Source for bait stations being as effective and cheaper.
Carey, J.R., Papadopoulos, N.T. et al. (2008). Age structure changes and extraordinary lifespan in wild medfly populations. Aging Cell 7:426–437. Source for adult lifespan.
Duyck, P.F. and Quilici, S. (2002). Survival and development of different life stages of three Ceratitis spp. reared at five constant temperatures. Bulletin of Entomological Research 92:461–469. Source for the stage durations by temperature.

Disclaimer This text is informational and educational in character. It does not replace an on-site agronomic assessment and does not constitute a prescription for the application of plant protection products. Rates, approvals and pre-harvest intervals change over time and differ between countries and crops; the label instructions and the national approvals always take precedence. The plant protection approvals shown on this site are issued by the Greek Ministry of Rural Development and Food and are valid in Greece only; they do not apply in other countries. Every intervention is made at the user's own responsibility, following an on-site assessment by a licensed agronomist. Pastopoulos Agronomics accepts no liability whatsoever for the use of the information above.