Bug wars: In Utah farm fields it's ladybugs vs. a plague of aphids

Bug wars: In Utah farm fields it's ladybugs vs. a plague of aphids
Ladybugs, joined by another insect, eat speck-like aphids infesting an alfalfa plant on a farm in Syracuse, Utah. (Thomas B. Szalay / For The Times)

James Barnhill has had a front-row seat to a tense natural battle in the farm fields of central Utah.

Due to a drought and record warm winter here, invasive insects called aphids have survived the usually frigid months to ravage alfalfa and wheat crops this spring.


Their ravenous opponents: legions of ladybugs.

Take a walk with Barnhill through any Utah alfalfa field and you'll see them, sometimes 10 ladybugs to a plant. But they are canaries in Utah's farming coal mine: such numbers suggest that a plant is infested with dozens of aphids.

"We have zillions of them," Barnhill, a Utah State University agriculture extension agent, said of the ladybugs. "They have just occurred naturally. We didn't order them or spread them. They just showed up and began reproducing on infected crops."

It's not clear how the ladybugs sense aphids, but scientists believe they follow chemical trails to their prey.

At 61, Barnhill has been helping farmers control insects for 30 years. And he's never seen such an aphid invasion. The most persistent pest for alfalfa growers has been the pea aphid, a green creature with long legs and antennae.

Barnhill told the Los Angeles Times that just about every alfalfa farmer in central Utah is overrun with the critters. "And," he observed, "lots and lots of ladybugs."

Farmers had hoped nature could beat back the aphid assault, but this infestation was too big even for the ladybug brigade.

"This is the first year ever that I've advised farmers to spray chemicals to control aphids," Barnhill said. In fact, he wishes he had done so sooner.

A product called Sivanto insecticide kills the aphids but spares the ladybugs.

"The spray gets into the vascular system of the plant and when the aphids suck the juices, they die," Barnhill said. "But since the ladybugs don't eat the plant, they stay alive."

Barnhill said that in its 30-day life span, a ladybug can consume up to 2,000 aphids. "But the warmer it gets, the faster they go through their life cycle, so we're hoping it doesn't get too hot here this spring."

And Barnhill just can't help himself: He can't help but watch in amazement nature's show of one insect reducing the devastation wreaked by another.

All he needs is some popcorn.

"It's amazing for all of us to watch these ladybugs," he said. "Most insects out there are probably good. There's just a few of them that cause us trouble."


For news from the West follow @jglionna