Help Slow the Spread of Asian Citrus Psyllid in California

[From the March 2016 issue of UC IPM's Retail Nursery & Garden Center IPM News]

Figure 1. Highly magnified adult Asian citrus psyllid feeding on citrus. [B. Grafton-Cardwell]

Until 2013, ACP was mostly found in Southern California, but has since been found in multiple locations in the Central Valley and has been detected as far north as the San Francisco Bay Area. The psyllid is well-established in coastal and inland Southern California and it is slowly establishing itself in Central and northern California. In the process, it is threatening California's commercial, nursery, and residential citrus.

ACP can transmit the bacterium causing an incurable and devastating citrus disease, huanglongbing (HLB) also known as citrus greening. It is imperative that ACP populations be kept as low as possible to reduce the risk that the psyllid finds and feeds on an HLB-infected tree and spreads the disease. To keep the psyllid from spreading, ACP host plants (citrus and close relatives such as orange jessamine and Indian curry leaf) in affected counties are under quarantine; they cannot be moved out of these quarantine areas. See maps of ACP and HLB distribution, quarantines in California, and tips for what to do at ucanr.edu/sites/ACP/Distribution_of_ACP_in_California.

We cannot stress strongly enough that retail nurseries and garden centers, residents, and landscapers can play major roles in minimizing the spread of this pest and HLB. Please read the guidelines below to learn more about what you can do.

Best Management Practices for Nursery and Garden Centers:

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  Figure 2. Huanglongbing (HLB) leaf symptoms. [B.Grafton-Cardwell]
  Citrus trees are treated with insecticides to remove pests when they leave wholesale nurseries and to keep ACP from feeding on them. However, these treatments remain effective for only about three months. Citrus stock should be sold before trees lose this protection. Stock that is in the retail nursery for close to 3 months should be returned or destroyed.
• If possible, place trees inside a screened-in structure to protect them against psyllids. If this is not an option, take advantage of ACP's preference for sunny, warm conditions by keeping citrus and other hosts under shade structures or even inside the store.
• As you are caring for and handling your citrus stock, carefully check the leaves and stems for psyllids. For photos and instructions on what to look for, see CaliforniaCitrusThreat.org or in Spanish, PeligranCitrusenCalifornia.com.
• If you see the psyllid, contact your County Agricultural Commissioner as soon as possible.
• Be sure your garden center or nursery sells or buys certified disease-tested trees from a reputable source. Uncertified trees may provide the insects with a source of the disease-causing bacteria they can pass on to other trees.
• Learn more about ACP by taking an online course for nurseries and garden centers. Go to class.ucanr.edu and look for the “Asian Citrus Psyllid & Huanglongbing for Retail Nurseries” course.

For Homeowners and Landscapers:

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  Figure 3. Asian citrus psyllid adults and nymphs feeding on new citrus growth. [M.E. Rogers]
  Citrus trees sold within an ACP quarantine area will have a blue or yellow tag indicating they must stay within the quarantine area. Know the quarantine boundaries and always comply with quarantines in order to protect uninfested areas.
• Learn how to carefully check the leaves and stems for psyllids and disease symptoms whenever caring for citrus.
• If homeowners or landscapers suspect they have seen the psyllid, advise them to immediately call the CDFA Hotline 1-800-491-1899. CDFA personnel will tell the caller if CDFA will be treating the reported trees or if the homeowner should manage the ACP population.
• A range of insecticides are available for ACP management, including products for use in a residential setting. Homeowners and landscapers can learn about about insecticides effective against psyllids and tips for application at UC IPM Asian Citrus Psyllid Pest Note.
• If you are in an ACP-infested area, handle green waste carefully. Dry out or double bag citrus trimmings from pruning before moving it offsite to prevent transporting ACP to new areas.
• If clientele think they have seen HLB disease, tell them to immediately call the CDFA hotline 1-800-491-1899. CDFA personnel will take leaf samples to confirm infection of the tree by a biochemical test.
• Take the online course about ACP and HLB in residential citrus: Go to class.ucanr.edu and click on the “ACP & HLB” link under “Master Gardener Courses.”

Be vigilant and help to protect California's citrus trees!