Emerging Tree Pests

The City of Irvine is assisting in educating the public on signs and treatment options for the Polyphagous Shot Hole Borer (PSHB) and Asian Citrus Psyllid and Huanglongbing (HLB).

Polyphagous Shot Hole Borer (PSHB)

The Polyphagous Shot Hole Borer is an exotic and invasive ambrosia beetle found attacking a number of tree species in Los Angeles, Orange, Riverside, and San Diego Counties. Commercial avocado groves, common landscape trees, and native species in urban and wildland environments are among the tree species being attacked. Trees that are susceptible may experience branch dieback, canopy loss, and, in some cases, tree mortality. The PSHB does not pose a threat to public health.

Under the Division of Agriculture and Natural Resources, University of California, the California Cooperative Extension is responsible for research and education of the PSHB, with offices serving every county in California. The Orange County University of California Cooperative Extension works in full partnership with government agencies, as well as individuals and private entities, to implement more efficient growing methods, solve pest management problems, and develop smart water-use strategies.  

View the Orange County Cooperative Extension presentation regarding the PSHB. Additional information on the PSHB can be found on the Cooperative Extension’s website at ucanr.edu/sites/pshb/

Questions may be directed to the Orange County UC Cooperative Extension:

Orange County UC Cooperative Extension
7601 Irvine Boulevard
Irvine, CA 92618
Phone: 949-653-1809
Fax: 949-653-1800

Asian Citrus Psyllid and Huanglongbing (HLB)

The City of Irvine and other surrounding cities are part of the California Department of Food and Agriculture's Emergency Program Against the Huanglongbing Disease. View the Notice of Treatment and the Proclamation of the Emergency Program, along with relevant maps regarding the Asian Citrus Psyllid and Huanglongbing on the state's websiteAn HLB quarantine is currently in place in parts of Los Angeles, Orange, Riverside and San Bernardino counties, which limits the movement of citrus plants and material to prevent the spread of HLB. Although HLB has not yet been found in a commercial citrus grove, more than 2,300 residential citrus trees in California have been infected with HLB and removed to limit the spread of HLB.

The Asian Citrus Psyllid, a tiny insect no bigger than a grain of rice, may go unnoticed on your citrus trees, but it could have devastating consequences for California citrus if not stopped. The Asian Citrus Psyllid feeds on citrus leaves and stems, and can infect citrus trees with a bacteria that causes a serious plant disease called Huanglongbing, also known as HLB or citrus greening disease. While not harmful to humans, the disease kills citrus trees and has no cure.

The best way to protect citrus trees from HLB is to stop the Asian Citrus Psyllid. Once a tree is infected with HLB, it will die. Diseased trees need to be removed in order to protect other citrus trees on the property, neighbors’ trees and the community’s citrus. Visit the Citrus Pest and Disease Prevention Program website for more information. 

If you have any additional questions, the City of Irvine Landscape Maintenance Division may also be reached at 949-724-7600.