Q: I have a lemon tree growing in a pot on my patio. It has been happy for several years and gets moved indoors for winter, but I now notice that some of its leaves are curling. What can cause the ...

Overwatered citrus trees will often have yellow leaves that are drooping or falling off, and the area around its roots will be soggy and bog-like. Sometimes, you'll notice a foul-smelling odor too.

Or treat the tree with a drench of imidacloprid (Bayer Advanced Fruit, Citrus and Vegetable Insect Control) once in spring after flowering or in early summer to prevent citrus leaf miner damage.

Citrus trees in containers grow best when provided some shade, especially during mid-day. Too much sun bleaches out exposed leaves, causing them to develop buff-colored blotches.

Citrus trees infected by citrus greening often have the Asian citrus psyllid. The adult insect is small (about 3 mm or ⅛ inch) with a distinctive 45-degree angled posture when present on leaves.

Lemon trees need to be regularly fed to promote healthy fruit production. “Feed [your lemon tree] monthly with a fertilizer ...

Researchers noticed that citrus trees on the edges of oak forests suffered fewer greening symptoms. With further investigation, the scientists determined that an extract in the oak leaves was ...

A version of this story appears in the February 2017 issue of National Geographic magazine. Citrus, in many ways, stands alone. So many cultivated species have come from so few primary ancestors.

Hornbaker encouraged residents with questions or those who may have seen insects on their citrus trees or have a situation requiring attention, to call CDFA’s Pest Hotline at (800) 491-1899.