Yellowing on citrus leaves is symptomatic for citrus greening disease

The assymetrical yellowing of citrus leaves, as shown here, can be symptomatic of citrus greening, or Huanglongbing. Lab tests will be required to determine whether the tree is infected with HLB.

ACP quarantines spreading through California

Only known host of ACP is citrus trees and plants Concern over the ACP relates to bacterial disease it can spread among citrus trees Regulatory quarantines affect movement of fruit and plant materials    

Santa Clara, and soon San Joaquin, will be two of the latest California counties to have Asian citrus psyllid quarantines as discoveries of the pest continue to be confirmed in California.

While an official quarantine has not yet been announced for San Joaquin County after psyllids were discovered on traps in Manteca and Lodi, California Department of Food and Agriculture officials have announced a 99-square-mile quarantine zone in in Santa Clara County.

Much of that includes the cities of San Jose and part of the city of Santa Clara. The highly-urbanized region contains retail nurseries that will now have to abide by federal and state quarantine regulations regarding the shipment of citrus trees and curry plants.

The quarantine zone also encompasses the entire San Jose International Airport.

The Santa Clara quarantine comes after a breeding population discovery of ACP was confirmed within the city of San Jose in early October.

A near simultaneous discover of psyllids was also reported on traps in the cities of Manteca and Lodi, both in San Joaquin County. Both were in urban settings.

For urban psyllid discoveries outside of southern California state officials continue to employ aggressive spray treatment protocols within about a half-mile of the initial discoveries. This includes foliar and systemic treatments of affected trees and increased sampling of areas around the find sites.

The chief concern of the Asian citrus psyllid is a bacterial disease it vectors called Huanglongbing (HLB), or citrus greening. The disease is fatal to citrus trees. There is no known cure for the disease, which is only known to impact citrus trees.

State officials say that they were able to test psyllids and plant material from the San Jose discovery for HLB. Those test results came back negative for the bacterial disease.

Quarantine impacts

The urban setting quarantines not only impact the movement of citrus fruit, but regulate the movement of citrus trees and ornamental curry plants from nurseries within the quarantine zones.

The quarantine prohibits the movement of citrus and curry tree nursery stock out of the quarantine area and requires that all citrus fruit be cleaned of leaves and stems prior to moving out of the quarantine area. Residents with backyard citrus trees in the quarantine area are asked not to transport citrus fruit or leaves, potted citrus trees, or curry leaves from the quarantine area.

Information on the ACP quarantine and its associated regulatory restrictions can be found on the CDFA website.

University of California experts on the ACP say the recent rash of psyllid discoveries in Central California were to be expected since citrus plants tend to be producing new growth at this time, and that is what the psyllid is attracted to.

The fact that trap discoveries of the psyllid are being made in greater frequency also suggests that populations of the invasive pest are reaching a threshold in California that indicates an even greater number of them remain undetected, but nevertheless out there.

In addition to Santa Clara County, ACP quarantines are now in place in Imperial, Los Angeles, Orange, Riverside, San Bernardino, San Diego, Santa Barbara, Tulare, Ventura, and portions of Fresno, Kern, and San Luis Obispo counties.

An HLB quarantine remains in effect for the Hacienda Heights area of Los Angeles after the 2012 discovery of citrus greening in a residential tree there. Information on that quarantine and host citrus plants that attract the Asian citrus psyllid are available online.

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