Citrus Psyllids Bribe Ants with Strings of Candy Poop

Asian citrus psyllids transmit a disease that can ruin your oranges. Even worse, Argentine ants protect them in exchange for the psyllids’ delicate ribbons of sugary poop, called honeydew. So, researchers are helping orange growers fight back with invisible lasers, ghastly wasps and more trickery.

TRANSCRIPT

This orchard is swarming with Argentine ants, but they’re not here for the juicy oranges.

They’ve found something way better.

They’re obsessed with these delicate candy ribbons …

… which happen to be coming out of the butts of these tiny insects: Asian citrus psyllids.

They suck sap from citrus trees.

And produce the prettiest of poops, called honeydew.

The ants ranch the psyllids like cattle, putting their lives on the line to protect their herd from predators.

This ladybug larva is easily deterred.

But this hoverfly larva takes more convincing.

Even more dangerous to psyllids is this tiny parasitoid wasp.

It’s looking for a host for its eggs.

But the ants are having none of that.

The psyllids and their ant allies have an even bigger threat.

Citrus growers who are desperate to keep the pests out of their orchards.

That’s because psyllids can spread bacteria in their saliva that causes a disease called citrus greening.

The disease turns leaves yellow and makes fruit green and bitter.

Citrus growers can spray pesticides, but those kill the helpful insects too …

… leaving the trees undefended when the psyllids inevitably find their way back.

Plus spraying only gets at some of the ants, since most are safely underground at any one time.

So let’s recap: it’s psyllids and their ant bodyguards vs. citrus growers, predators and parasites.

Still with me?

Because psyllids are so tough to get at, citrus growers decided to take out their ant accomplices instead.

By studying the ants’ behavior, researchers at the University of California, Riverside, found a weakness they could exploit.

Ants follow the easiest path from tree to tree.

They’re all about efficiency.

They turn the orchard’s irrigation pipes into mini highways.

Researchers set up sensors on the pipes that use invisible infrared beams to measure how many ants go marching through.

In the most trafficked areas, researchers spread these tiny biodegradable balls.

They’re soaked in sugar water laced with a slow-acting insecticide.

The ants slurp up the poison and bring it back to share with the colony.

This targeted technique uses just a fraction of the pesticide that spraying would.

With fewer of their bodyguards around, the psyllids are more exposed to their enemies.

The parasitoid wasp moves right on in.

And lays an egg on the psyllid’s soft underside.

That wasp egg hatches and the larva right here burrows into the psyllid, devouring it from the inside.

When the wasp is all grown up, it chews its way out, right through the top of the dead psyllid.

Glad they’re on our side, huh?

It’s a story of unlikely allies, fighting an ongoing battle, for the sweetest of rewards.

OK, remember those ferocious hoverfly maggots beating up the ants?

When they grow up, they’re some of the most athletic fliers in the insect world.