Pest Of The Month: Mediterranean Fruit Fly

During routine fruit fly monitoring in June, a trap containing Mediterranean fruit flies was collected in Palm Beach County, by a Florida Department of Agriculture and Consumer Services (FDACS) inspector. Since the initial find, flies have been found on traps in mango, loquat, and sour orange trees. This is the first major outbreak of Medfly in Florida since a nine-county eradication program in 1997 and 1998.

The species is native to sub-Saharan Africa and is not known to be established in the continental U.S. When it has been detected in the U.S., infestations have necessitated massive eradication and detection procedures to prevent establishment.
Because of its wide distribution over the world, its ability to tolerate cooler climates than most species of fruit flies, and its wide host range, it is ranked first among economically important fruit fly species. Its larvae feed and develop on many deciduous, subtropical, and tropical fruits, and some vegetables. The flies’ eggs are laid in the fruit and develop into maggots causing the fruit to rot. They then emerge as adults once the fruit falls to the ground.

Medflies breed continuously when host fruits are available. Population growth may be explosive, as females are capable of producing hundreds of eggs.

The pest can move rapidly. Once established, eradication efforts may be extremely difficult and expensive. In addition to reduction of crop yield, infested areas have the additional expense of control measures and costly sorting processes for both fresh and processed fruit and vegetables.

In Florida, a joint state/federal cooperative fruit fly program monitors fruit fly traps across the state. The traps are checked every 21 days, and more frequently in some high-risk areas.

Once the area of infestation is delimited, there are a number of tools and techniques available to control the outbreak. Additional traps are placed around each positive find to help delineate the area of infestation.

Control measures include foliar spot treatment of host trees with Spinosad (Dow AgroSciences), an insecticide approved for use on organic crops. Other treatments include soil drenches to target pupating flies and fruit stripping of infested trees.

Another important tool is the release of sterile Medflies, a biologically-based reproduction control method. Since 2002, a cooperative effort between USDA and FDACS/DPI initiated a program where millions of sterile Medflies are released throughout high-risk areas to prevent potential infestations.