Emerging Tree Pests

Dear Community Partners,

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.

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.  

On May 14, 2019, the Orange County Cooperative Extension made a presentation regarding the PSHB. View the presentation here. Additional information on the PSHB can be found on the Cooperative Extension’s website through the link below:


Questions may be directed to the Orange County UC Cooperative Extension Monday through Friday between the hours of 7:00 a.m. - 4:00 p.m.:

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

Additionally, the Asian Citrus Psyllid and Huanglongbing, 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.

Thank you,

Mark Steuer, Director
City of Irvine Public Works Department