Mediterranean Fruit Fly

 The Mediterranean fruit fly has reappeared in California!


Periodically, in the world of gardening and agriculture, a cry goes out across the fields, farms, and front porches of the world, announcing that a medfly has been found. In this case, a medfly was found in Half Moon Bay.

Adult medfly (Alvesgaspar) CC BY-SA 3.0

You might think that a tiny fruit fly is No Big Deal, but this short, squat, orangish flying insect has the dubious title of World’s Worst Agricultural Pest.


​The California Dept. of Food & Agriculture estimates that a permanent infestation of the Mediterranean fruit fly, or Medfly, would cost California businesses nearly $2 billion a year!

About medflies

Native to sub-Saharan Africa, medflies (Ceratitis capitata) have slowly been making their way around the globe, usually riding on fruit and other infested crops. Medflies are about 1/4” long. They have a black thorax, marked with silver, and a tan abdomen with dark stripes. The wings are clear, with two light brown bands and gray flecks at the base. Their eggs look like those of other fruit flies: they look like tiny white bananas. Larvae are white, legless, and pointed at the back end. Pupae are encased in a hard, shiny brown puparium.

Medfly larva (Daniel Feliciano) CC BY-SA 4.0

Damage caused by medflies

Medflies lay their eggs in the skins of over 250 different fruit, nut, and vegetable crops. When the eggs hatch three days later, the maggots burrow into what we normally eat, making it inedible. Once maggots have eaten their fill, either the rotting fruit falls, or they drop to the ground where they pupate in the soil. In one week, an adult emerges and the whole cycle begins again.


Crops affected by the medfly

It would probably be easier to list the crops not affected by medflies, but this should give you an idea: apples, apricots, avocados, cherries, figs, grapes, grapefruit, lemons, limes, melons, nectarines, oranges, peaches, pears, persimmons, plums, pomegranates, sweet peppers, tangerines, tomatoes, and walnut.


The ripple effect

Like most things in life, this situation is not limited to bug-infested food plants. Commercial and home growers will end up using more pesticides to counteract this insect, which can lead to more ground water contamination and chemical resistant pests. Also, areas with medfly populations are unable to sell their produce, infested or not, to other states and other countries. Finally, native plants that produce fruit or nuts can also be attacked by this pest.


Medfly controls

The first appearance of a medfly in California took place in 1975. I remember hearing about it in the news - everyone was talking about it. The government declared a “state of emergency” and 100 square miles were placed under quarantine, and 600 million sterile male medflies were released to interrupt breeding. Malathion was sprayed all over the place. It cost $1 million and took a year, but the medfly was eradicated. For a time.


When the medfly returned in 1981, Governor Brown delayed aerial spraying of malathion, claiming environmental concerns. That was when we learned that medflies reproduce and feed at astounding rates. In that case, the medflies needed only one month to destroy millions of dollars of crops, and to threaten billions more, over an area of 530 square miles. When it was realized just how devastating this pest could be, the California National Guard was called upon to create highway checkpoints to confiscate infested produce.


Now, when a single medfly is spotted, it is checked for gender and fertility, and then all the stops are pulled: aerial spraying, ground spraying, trapping, irradiation, releasing sterile male medflies, public information, and quarantines. Since 1985, medflies have been found in California in 2007 (Dixon), 2008 (El Cajon), and in 2017.


What can you do?

First, never, ever, EVER smuggle fresh produce, plants, or soil from infested areas into uninfested areas. Do not mail fresh produce into uninfested areas either. For more information, contact the California Dept. of Food and Agriculture at (650) 363-4700.

IF YOU THINK YOU SEE EVEN ONE MEDFLY, PLEASE REPORT IT!