Original image courtesy of mcatalena of Flikr

California is famous for its oranges and other citrus crops.

This is not your seasonal Flu shot advisory. Nor is this a post about home wrecking pests. There is a citrus quarantine in the San Francisco Bay Area, as those pesky bugs mean business.

Do you like citrus?

Maybe you’ve heard stories about the disappearance of oranges in Florida. The cause is orchard destruction due to citrus greening – a disease which destroys fruit and eventually kills trees. Since it was first discovered in Florida, it has now infected 90% of groves in the state. No tree is naturally resistant and, while scientists and farmers race to find a solution, there is no treatment for the disease. (source)

California may have strict agricultural transportation rules, but citrus greening has spread to many areas of our state as well. Including the Bay Area.

So how does this impact homeowners? Well, do you own a citrus tree? One organization estimates that more than 50% of Californians have a citrus tree on their property. Even if you are not a citrus farmer, you probably enjoy the fruit and want to keep your tree healthy. If you have a citrus tree, plan on getting one, take fruit from friendly neighbors, or purchase fresh citrus products outside of grocery stores, the following information is important.

What is it? Citrus greening is a bacterial vector disease most commonly spread by invasive insects. While journalists typically call it citrus greening, most scientific articles call it by the Chinese huánglóngbìng, shortened to HLB. There are two known vectors for HLB: the Asian citrus psyllid (Diaphorina citri) and the African citrus psyllid (Trioza erytreae). Both psyllids are so small they are usually unnoticed, and their eggs may not be visible to the naked eye.

There are many guides to recognizing symptoms of citrus greening, so I won’t go into detail. Please use these links to the Univeristy of Florida page, the Citrus Pest & Disease Prevention Program website for California, and the University of California Asian Citrus Psyllid Distribution and Management page which have plenty of information on identification and prevention. Though there is no cure for the bacterial infection, the vectors can be destroyed with insecticides to prevent further spreading.


Prevention is key to survival, so if you believe your plant is infected or you live in or around quarantine areas there are certain habits you should learn to adopt. Here are the primary rules:

  1. Prevent transportation!

This is straightforward. Do not bring any citrus plant or part of plant from a quarantine area to an area outside of quarantine. If your home is outside of quarantine, you can bring your fruit to a friend in quarantine, but not vica versa. If you go to a nursery inside quarantine, they can still sell citrus trees, but these will be tagged to notify you they are required to remain within quarantine zone, and it is the buyers’ obligation to comply and to know the quarantine boundaries. Thankfully, the maps are readily available online in a number of locations. (Here are two: one by CDFA and one by UC.)

But it’s not just transportation of fruit and live plants that can spread the vector. Cut branches may pose the greatest threat to the spread of the HLB. After a branch is cut, the psyllid and its eggs may remain on the limb and leaves for days. A Silicon Valley local has a good, concise video on pruning trees and proper disposal methods to prevent spreading.

  1. Report it!

If you do suspect your tree to be infected, please report it to the California Department of Food and Agriculture Toll-Free Pest Hotline at 1-800-491-1899. Take all preventative measures to keep it from spreading, especially if you have other citrus trees in your garden. If you act carefully, your other tree(s) may never become infected. Consult professionals for the best information on dealing with an infected tree.

  1. Do your research!

The quarantine boundaries can always change. Stay up to date and check the map before you buy plants or travel with home grown fruit. Maybe down the line, successful treatments and immune plants will be developed, so keep an eye out for those in the long run.

  1. Act with caution!

If you’re unsure, better to be on the safe side. Farmers who rely on their groves for income are taking extra measures to protect the grove by acting as though it is already infected. Through precautionary measures, they are less likely to become infected, and if they do, it will be on a smaller, more controllable scale they are already prepared to handle. As a homeowner, be cautious – prevention might save your favorite garden feature!