My grandma has a Meyer lemon tree that’s been producing a bumper crop of lemons for decades. Each year the ladies in her bridge club, her bowling partners, and our family eagerly await our annual allotment. It’s about more than a bag of lemons: it’s time spent with Grandma; it’s the kids’ lemonade stand; and it’s the exchange of lemon preserves with neighbors and friends.
As a multi-generation Californian, I’ve taken the abundance of citrus around me for granted. 80% of the country’s fresh citrus comes from our state, and it’s estimated that California has as many backyard citrus trees as commercial. However, a new citrus pest is threatening to destroy our precious trees.
Be afraid, be very afraid!
The Asian citrus psyllid (sill-id) is a tiny insect that spreads the Huanglongbing (Wong-long-bing) disease (HLB), aka Citrus Greening, while feeding on citrus trees. HLB presents itself in the form of bitter inedible fruits, yellow mottled leaves, tree decline and eventual death. After an infected psyllid makes contact with a tree, it can take several years for HLB symptoms to appear.
The Asian citrus psyllid was first identified in Florida in 1998. 7 years later the state confirmed its first HLB infected tree. Florida sprang into action in an attempt to stave off an agricultural catastrophe, but had minimal results. A 2015 Florida University study stated that 80-90% of Florida’s commercial groves were infected with HLB. There has been a 41% drop in the state’s citrus yield since the disease was identified in 2005.
Asian citrus psyllid in our own backyard
While Florida is over 2,000 miles away, the Asian citrus psyllid and HLB have become alarmingly close. In November 2015 the psyllid was identified in Daly City and Pacifica. There’s now a citrus quarantine within San Mateo and San Francisco counties. Residents and nurseries must not move trees, scions for grafting, or additional vegetative matter (not the fruits) in or out of the quarantine boundaries. The quarantine begins at the south end of San Francisco and continues down to Pacifica and Milbrae.
We need you!
Backyard citrus owners constitute the largest group of citrus growers in California, and as such, we must be the vanguard to stopping this disease. It’s not just my grandma’s lemon tree or the state’s $2 billion citrus industry that’s at stake - it’s a way of life unique to Californians.
There is no cure for HLB and the current management practices are concentrated on preventing citrus trees from being exposed to the psyllid. We can fight this deadly disease by following strict quarantine rules and actively monitoring our citrus trees for the psyllid.
Monitoring to save citrus trees
The Asian citrus psyllid emerges when the weather is warm and a tree is flushing; small new leaves emerge in bunches at branch tips. Flushing is often concentrated in the spring, but with our moderate Mediterranean climate, young trees might flush at other times, too. Monitoring should occur on a monthly basis in the spring and anytime the tree has new growth.
Look for two forms of the psyllid when monitoring: the winged adult and the juvenile nymph. The adult psyllid feeds off the tree’s leaves with its head down and its rear-end in the air at a 45° angle. This body position and a dark brown band along the base of its wings are unique identifiers. The juvenile nymph is flat, oval and yellowish tan. It is easy to discern by the copious amounts of waxy tubules produced from its rear end. Adults and nymphs are very small, and a hand lens will help with identification.
What to do if you identify an Asian citrus psyllid
It is critical that you call the CDFA hotline at 1-800-491-1899 if you think you have identified the Asian citrus psyllid. Agricultural authorities will let you know if you are in a quarantined area and will discuss treatment options.
Our backyard citrus trees are just as vulnerable as the state’s commercial groves. Please be diligent about monitoring for the Asian citrus psyllid to prevent the spread of Huanglongbing disease. Our friends, families, and the entire nation depend on us to preserve California's fresh citrus.
Have a backyard citrus tree in San Francisco? Register it with Just One Tree, a non-profit dedicated to creating urban self-reliance through a tree crop.
Not sure what to do this summer, but know it should involve road tripin' and citrus. Check out California's citrus state park in Riverside, CA.
For more on the Asian citrus psyllid, including videos and management info, checkout the UCANR's Asian citrus psyllid website.