From left to right, almond kernel damage caused by leaffooted plant bug feeding during the early to middle season.
From left to right, almond kernel damage caused by leaffooted plant bug feeding during the early to middle season.

The leaffooted plant bug is one of those California almond pests that rears its ugly head one year, only to be relatively scarce for the next several seasons.

Although this season is shaping up to be worse than the past few years, it still isn't as bad as 2006, said David Haviland, a University of California farm advisor in Kern County.

That year, the inch-long bug caused more than just spotty damage throughout much of the stae's almond production area.

The pest inserts a needle-like feeding tube through the almond hull and the soft shell to feed on the developing kernel.

The process may cause the immature nut to shrivel or abort, or it may cause the nut to gum internally.

The bug itself is difficult to scout for because it moves out of sight when spooked.

Gummosis is a sign of feeding that can be easily scouted.

If growers or PCAs notice gummosis in nuts, they should look more closely for the bug, Haviland said.

Leaffooted bugs favor the Fritz variety over others, followed by Aldrich, Sonora and Monterey, says Mel Machado, special projects coordinator for Blue Diamond Growers, Modesto.

Garrett Bowman, a Salida-area grower, says he's found the pest in some of his orchards.

Because of their elusive nature, "they're very difficult to monitor for," he says.

Machado says he's heard reports of the pest from Oakdale south to Kern County.

"It's a huge deal in almonds when you get them," he says.

Warning issued for leaffooted plant bug in almonds

Franz Niederholzer, a UC farm advisor for Yuba, Sutter and Colusa counties, says he's heard reports of the pest in orchards as far north as Yuba City.

"Leaffooted plant bug is really difficult because it's a strong flier," he says. "It comes in, does a lot of damage and moves on."

One of the few effective treatments, pyrethroid, is a broad-spectrum insecticide that also kills beneficial insects.

"The only teratment is very disruptive to IPM (integrated pest management) programs, so it's a real challenge to decide whether you need to treat or not, even though you have this huge economic threat hanging over your head," Niederholzer says.

Because the pest is sporadic, researchers have difficulty studying it.

Even today, little is known about the biology or population dynamics of this native insect.

"It was a really warm winter, so insect pressure came on early," he says. "But we don't know if this caused the problem."