According to UC Integrated Pest Management guidelines, the leaffooted plant bug can cause two types of damage to pistachio nuts. The first is an epicarp lesion early in the season, similar to that caused by other true bugs which use needlelike stylet mouthparts to probe nuts to suck out plant juices.

Nuts damaged shortly after bloom turn black and drop. If the bug damages nuts during kernel enlargement, the tissue can turn brown and necrotic. The outside often becomes sunken and appears almost water soaked.

Second, even after shell hardening in June the bugs can cause damage known as kernel necrosis which is invisible on the outside shell. The only exterior sign can be a brown pinpoint mark.

Cut the nut open, and the kernel may appear darkened and often develops a sunken or distorted area. An off-flavor can occur.

If the nuts are damaged during high humidity, fungal breakdown may cause the nut to turn slimy, ­ referred to as stigmatomycosis.

Brad Higbee, director of entomology research for Wonderful orchards in Shafter, Calif., saw high leaffooted plant bug populations in almonds, pistachios, and pomegranates this spring. The company treated all three crops and retreated the pomegranates, due to a large jump in bug numbers in August.

So far, it appears the pistachio treatment was effective.

“We have just started the pistachio harvest and I’m not aware of any large populations yet,” Higbee said. “It would not be surprising if it occurred.”

Higbee is also involved in field and laboratory assays to determine the efficacy of various insecticides. He says some entomopathogenic fungal products hold promise.

He is also working on trapping methods including the development of synthetic and natural attractants, plus learning more about the bug’s basic biology.

Higbee is part of a research project led by UCCE Merced County entomologist Andrea Joyce to clarify the two species of plant bugs, ­ Leptoglossus clypealis and L. zonatus, ­and map its distribution throughout the Central Valley.

So far, orchard surveys from Chico to Bakersfield have found L. clypealis as the predominant leaffooted plant bug in almond and pistachios. L. zonatus has been the overwhelming species in pomegranates.

UCCE’s Tollerup is conducting research into large bug management in pistachios and its dispersion into neighboring pistachio and almond orchards. Part of the project will evaluate various insecticides for almonds and pistachios, and determine chemistry longevity under field conditions.

Under laboratory conditions, Tollerup will also study whether evaluated insecticides are feeding deterrents or repellents.