Drones carry beneficial insects to combat pests

Organic farmers often count on a helping hand from beneficial insects. Getting these critters into the field can be laborious, but in recent years another option has come along: sending in the entomological equivalent of the 82nd Airborne.

While taking a biocontrol class at Cal Poly San Luis Obispo five or six years ago, Chandler Bennett started thinking about what else could be done with drones—then an emerging technology—in addition to aerial photography and decided using the craft to introduce beneficial insects might just fly. After a few years of experimenting and testing, Parabug was born.

"We can pretty much put out any commercially reared insect or arachnid," such as predatory mites, green lacewing eggs and cryptolaemus beetles, he said. "We can even do some parasitoids when they're in their pupae stage."

His drones are set up mainly to drop predatory mites into strawberry fields to go after spider mites, but the Salinas-based Bennett—who works full-time managing strawberries—has also worked with pretty much every crop grown in Salinas Valley.

"We've even done quite a bit in organic almonds, table grapes, raisin grapes, winegrapes," Bennett said.

One of his customers, Eric Morgan, called on him to help bring green lacewing eggs into his vegetable fields. Morgan works as vice president of environmental science and resources for Soledad-based Braga Fresh.

"We've been doing it by hand, and when I would check on the progress, I'd find where they just dumped the bag on the ground," Morgan said. "If we're going to have any chance of having the beneficial insects work, I'd think that we'd want to evenly distribute them over the entire area."

So far, he's used the eggs-by-air method on fields of iceberg lettuce, romaine lettuce, cauliflower, broccoli, sweet baby broccoli and celery.

"We target fields that have higher levels of aphid in them," Morgan said. "The green lacewing, in the juvenile stage, is a predator of all aphids."

Green-lacewing larvae tend to have diverse palates, according to the University of California. They also go after mealybugs, psyllids, thrips, whiteflies, small caterpillars and leafhoppers. Bennett said that while most of his business—about 90 percent—has been coming from organic growers so far, conventional growers have also made use of the technology.

"It's tough to get in with a spray rig because of field conditions," Bennett said. Also, "strawberry guys are limited on the chemistries that they have," he added.

Unlike aerial photo missions, which fly at altitudes of 400 or so feet, Parabug drones will operate as low as 10 feet to cover a strawberry field, or 10 to 20 feet above the top of a tree canopy. Insects or eggs are carried in revolving cylinders underneath the drone; the contents are released through holes in the cylinders. In addition to the insects, a carrier agent—often vermiculite, rice hulls, rice bran or sawdust—is used.

"I like to tell people it's kind of like a salt shaker," Bennett said. That action is especially important with the predatory mites, which otherwise might not want to make the leap.

"The mites, they like to crawl to the top of things, toward light," Bennett said. "That rotation action helps keep them uniformly mixed in their carrier."

He said the toughest sell so far has been with strawberry growers, "which is kind of ironic, because I made it for strawberry guys, primarily," Bennett said. "They have some concerns about being right on the plant." To address those concerns, Bennett will take the drone to a grower's field for a demonstration.

Bennett works with independent operators around the state and has plans to expand to Arizona and Florida. The insects or eggs to be delivered usually come from breeders working with the grower, although Bennett does work with vendors who can help growers new to the use of beneficial insects.

Morgan, who began working with Parabug last year, said he plans to stick with it.

"You can't tell a natural-reared, Mother Nature's lacewing from one that we purchased," Morgan said. "I can't quantify how truly effective it is, but it's one of the things that we do because we think it gives us a better chance to harvest our organic crops."

(Kevin Hecteman is an assistant editor of Ag Alert. He may be reached at khecteman@cfbf.com.)