These Mites Rain Down To Save Your Strawberries

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Two tiny mites duke it out on strawberry plants throughout California. One is a spider mite that sucks the juices out of the delicious crop and destroys it. The other, persimilis, is a crafty predator that growers drop by the thousands from high-tech drones to protect their fields.

Additional Resources

  • Growers hire companies like Parabug to distribute biological control agents like predators and parasites to defend crops from pests.
  • Entomologist Christian Nansen and engineer Zhaodan Kong are studying ways to automate the discovery and treatment of agricultural pests using drones armed with a special camera to identify subtle signs of infestation and distribute biological control agents to infested crops.
  • Information about garden and landscape pests like spider mites come from the University of California Statewide Integrated Pest Management Program (UC IPM).
  • Koppert Biological Systems sells predators to control spider mites.


This mite is super small — roughly the size of a grain of salt.

But its oversized appetite makes it one of the most daunting threats farmers face.

Unchecked, they would devastate crops like these delicious strawberries.


You’ll know these mites by their calling card: dry rusty leaves.

And by these messy webs that give our tiny foe it’s name: The twospotted spider mite.

It’s not really a spider, but it is an arachnid — so it’s related. And it does have two dark spots.

It sucks the juices from the strawberry plants’ leaves with its needle-like stylet.

Sip after sip, row after row.

Pretty soon the leaves won’t be able to absorb enough sunlight to fuel the plant.

Farmers use pesticides, but spider mites quickly become resistant.

So farmers formed a strategic alliance ... with a bolder, badder mite.


Persimilis is a predator.

It only eats other mites … and it’s favorite is the twospotted spider mite.

The tiny carnivores arrive in bottles packed with vermiculite, a lightweight mineral that gives them something to hold on to.

But spreading them by hand takes a ton of time.

So some farmers are taking this old battle to the next level.

They’re calling in air support.

Drones, packed with persimilis!

The predatory paratroopers rain down on the field below.

The moment they land, the bright red persimilis start hunting down the unwelcome vegetarians.

Persimilis are blind.

They track down their prey with palps that sense vibrations and smells.

Plants under attack by spider mites release pheromones.

Those signals lead persimilis mites right to their prey.

They tear into their prey with biting pincers called chelicerae. And slurp out the innards.

Persimilis mites have a taste for eggs too. Caviar anyone?

Mmmmmmmm …

Eventually this skilled hunter is so successful it exhausts its only source of food.

When the feasting’s done, the persimilis mites can’t survive.

The field goes quiet.

The strawberries are safe …

At least until the spider mites return, to face another fight from the skies.

Hey it’s Laura.

You know who else has mites? You!

They’re on your face … and they’re getting busy there.

They might also have neighbors: head lice.

Itchy, blood-sucking acrobats that turn your head into their personal jungle gym. Enjoy!