New weekend psyllid finds include Fresno County

The most recent find of the Asian citrus psyllid pest over the weekend was made in Fresno County for the first time.The most recent find of the Asian citrus psyllid pest over the weekend was made in Fresno County for the first time.The feared Asian citrus psyllid appears to be spreading rapidly across the citrus belt with new finds over the weekend in Fresno County between Orosi and Orange Cove and near the Tulare County towns of Strathmore and Ducor.

All three of the latest finds were made in commercial citrus groves, bringing the recent tally to nine discoveries in Tulare County and one in Fresno County.

According to Tulare County Agriculture Commissioner Marilyn Kinoshita, the find in Fresno County is near the intersection of Hills Valley Road and Floral Avenue near the Fresno-Tulare County line. The area is northeast of the town of Dinuba, where the pest was discovered in a residential citrus tree earlier this month.

The separate discoveries over the weekend in Strathmore and Ducor are outside established quarantine zones for the pest. The pest has also been trapped near Exeter and Porterville.

“This shows the pest is the spreading," said Kinoshita, noting that UC Extension pest management expert Beth Gafton Cardwell had predicted recently more Asian citrus psyllid finds in the area in the fall.

The new finds are making it more likely that the quarantine zones will be expanded just in time for the new citrus season. The zones would impact Fresno County for the first time.

The zones include 90 square miles around Porterville, a new Kern County zone near Wasco that is 88 miles and now a new zone being developed in northern Tulare County and southern Fresno Counties.

Citrus stock within the zones may not be moved outside the zones without a permit and commercial citrus fruit must be cleaned of all leaves and stems before it can be shipped.

As of yet, the insects are not carrying the dreaded citrus greening disease or huanglongbing (HLB) that kills citrus trees and is spread by the psyllid.

Backyard citrus is a major problem since homeowners don’t typically watch for the tiny insect. Some 60 percent of homes in the state have citrus and there are more backyard citrus trees in the state than commercial citrus trees, said Grafton-Cardwell.

Researchers are working on several fronts including developing a rapid detection test that “sniffs VOCs (violatile organic compounds)” put out by a diseased tree.

Both cold weather and hot weather slow the insect down, a benefit of the California climate.

Researchers have a few tricks up their sleeve when disease does come here. One involves using the vector for another citrus disease — the mild strain of Tristeza (CTV) spread by aphids that causes little production losses compared to severe strains.

Grafton Cardwell said the idea is to use the CVT virus as a carrier into the tree that would inoculate the tree from HLB. Another idea is to breed a psyllid population that can not carry HLB and flood the area where these harmless insects can disrupt the mating of HLB carrier psyllids.