In October, Mediterranean fruit flies were discovered in an area of Los Angeles. California is a big farming state, and this was serious news for farmers. The solution to the problem may seem a little unusual: releasing millions more of the flies.
The Mediterranean fruit fly, often known as the “Medfly”, is one of the most serious threats faced by farmers worldwide. Once the pest makes its way into an area, it can be very hard to get rid of.
The flies lay their eggs in over 300 kinds of fruits and vegetables. When the eggs hatch, they turn into worm-like larvae that can ruin these products.
(Source: ARS/USDA [Public domain], via Wikimedia Commons.)
The problem is that it can be hard to know that the flies are there until it’s too late. That’s because the fruits and vegetables still look normal even after the eggs are laid inside. So the damaged fruits and vegetables can be sent to other places, allowing the Medflies to spread.
Mediterranean fruit flies were first found in California in 1975, but they really became a problem in the 1980s. Since then, the state has been taking steps to keep the flies under control.
Three Mediterranean fruit flies were discovered in a Los Angeles neighborhood called Leimert Park in October. To stop the problem from spreading, the government set up a large quarantine area, which means that no produce (fruits, nuts, or vegetables) can be moved out of that area. The quarantine area is 90 square miles (233 square kilometers).
(Source: CDFA.)
That may seem extreme, since only three Medflies were found, but experts believe there are probably more out there. “It’s really important to get on top of this fast,” said entomologist Jason Leathers.
Luckily, California has developed a program to control Medflies, and it’s been working well for 30 years. The plan involves using planes to drop millions of Medflies over the area. That may sound like a bad idea, but it’s actually a tricky way to make sure that Medfly numbers go down.
The trick? The airplanes only drop male flies, and all of them have been treated so that they can’t help produce new fruit flies. The males are sterile. This means that even though they can mate with female fruit flies, the eggs produced will never grow or hatch.
(Source: Jari Segreto [CC BY 2.0], via Wikimedia Commons.)
In the early growing stages, these sterile flies are grown in labs in Hawaii and Guatemala. The insects are colored with a special dye to make sure they won’t be confused with wild Medflies.
These immature insects are then sent to California in huge numbers – around 200 million a week. They’re raised until they’re adults, then they’re treated to make them sterile. Finally, the flies are released from airplanes, using a special method designed to spread them out over a wide area.
The plan has worked well in the past. The government says that the number of infestations (times when flies are found) has been cut by over 90%.
To deal with the problem near Leimert Park, the government will be dropping two airplane loads of sterile Medflies every week.
Did You Know…?
Mediterranean fruit flies are just one kind of fruit fly pest that California is fighting. Over the last year, the state has had to take steps to get rid of three other kinds of invasive fruit flies that are serious pests for farm crops.