Name: Why the government drops flies on California
Uploaded: 2025-06-17T15:16:25.000Z
Duration: 6 min 36 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

The Mediterranean fruit fly, or medfly, is an invasive pest in California.

Medflies lay their eggs inside fruit and breed incredibly fast.

But today, and almost every day, aircraft hired by the California and federal governments are going to drop millions of them over Southern California, and over the Los Angeles metro area specifically.

California experienced recurring infestations from 1987 to 1994.

So in 1994, California began a two-year test to determine if releases of sterile flies as a preventive measure would reduce the size and scope of the infestations.

And during that two-year test period, California experienced zero infestations.

So in 1996, the Medfly Preventive Release Program began, and the program currently today is 1,750 square miles.

So the plan is, breed male flies in areas where it's safe to do so, because they're already established.

Sterilise the flies when they're in the pupal stage with radiation, and tag them with an ultraviolet marker dye.

To be clear, irradiating something does not make that thing radioactive, but it does make the flies sterile.

Then they're shipped here, hatched, bundled up into planes, and dropped onto California, where their job is to out-compete any wild medflies that have made it to the area.

We maintain our colonies offshore in areas where medfly is already established, because we don't want to risk that any flies escape our facility and start an infestation.

We're sourcing approximately 24 million sterile males per day, seven days a week.

Our staff inspect the flies for sterility.

Then they're poured into a hopper that sits above a volumizer.

The volumizer measures out the desired amount of pupa, and it will distribute it around the perimeter of each tray.

When the flies emerge from the pupa, they'll migrate to the center of the tray, where there are two pieces of agar, which will serve as their food and water source during incubation.

So then they're stacked into towers with our goal of placing one million pupa in each tower.

Those towers are moved to an incubation room.

After two days, most of the flies will start emerging.

On the third day, we place one milliliter of ginger root oil under each tower.

Ginger root oil contains a naturally occurring compound that increases the chance that those sterile males will have successful matings.

If female medflies that have arrived in shipping containers, or the post, or traveller's baggage mate with these, the eggs will never hatch.

Which means there's nothing burrowing through the fruit to destroy it, and no population explosion.

We will typically load six to twelve towers into a refrigeration trailer.

The flies will enter a chill coma, so they'll essentially be immobilized.

We have a specially engineered vacuum that will vacuum the empty pupa casings from the perimeter of each tray, but leave the flies in the center of the tray.

We will process those adults and load them into the release box that's then transported to the aircraft.

Those boxes contain anywhere from 50 to 130 pounds of flies, depending on the release area and the release rate.

It's approximately six to nine million flies.

And while hundreds of millions of flies sounds like a huge amount, it's actually not that many over an area the size of Southern California.

The aircraft are equipped with the release machine that has an AC unit that keeps the flies in an immobile state until release.

Drop time can vary from 30 minutes to an hour.

The aircraft are traveling at 161 miles per hour when they're releasing, so the volume of those flies are distributed fairly evenly throughout the target area.

If you were to see the plane flying overhead, you would not see the flies falling from the chutes, especially at the altitudes that we release, which are typically around 2,000 feet above ground level.

Big numbers are scary, but I did the maths, and they're aiming to have a density of about one sterile fruit fly every 20 to 40 square meters across thousands of square kilometers of Californian cities and farmland.

That density is orders of magnitude less than all the insects already out there, and that includes the quarantine areas.

We should talk about the quarantine areas.

California deploys approximately 100,000 exotic fruit fly detection traps throughout the state.

The insect detection traps are collected from the field and they're transported to our identification unit.

The flies are screened under a UV light, looking for the presence of the marker dye, so we're able to identify and differentiate a sterile fly from a wild fly.

If we detect two wild met flies within three miles of one another, or a larva, a pupa, or a mated female, we will consider that an infestation.

And that triggers a response, so there will be increased delimitation trapping to identify exactly where that infestation's occurring.

The rate of release of steriles will increase, as well as possibly fruit removal within a particular area.

As I record this, anyone growing fruit in more than 150 square kilometers of the LA metro area just can't legally sell it or even give it away to avoid the chance of spreading the infestation.

There are other larger quarantine areas out in the farmland that makes up a lot of this region.

In theory, there is a possible video titled I Released Two Million Fruit Flies Over Los Angeles, and yes, I want to press that button.

But unfortunately, there isn't a spare seat on the plane, and plus, the quarantine area includes under and around the approach paths to Los Angeles International Airport, so flying it is not an easy job and they do not want the distraction.

But I can show you a shot from inside the release tubes as millions of fruit flies are slowly dropped over LA.

We always want to have fresh, viable flies distributed into those regions, so we're releasing every three to four days.

The goal is to release sufficient numbers of sterile males into the environment to prevent any wild females that are introduced from finding a wild male and reproducing.

So it's essentially biological birth control.

Well, in the area they're dropping flies, there used to be seven or eight infestations a year on average, each one needing quarantine and pesticides and a huge amount of effort.

Since they started the program, about one a year.

Compared to the cost if medflies got established here, it's a pretty good deal.