I’ve said for many years that my role in my plant realm, is to “solve others’ gardening dilemmas” via consultations, classes and personalized instruction.
One such gardening dilemma that all San Diego gardeners face with any type of citrus (lemon, lime, orange, grapefruit, tangerine, kumquat, etc.) are “curled leaves.” I often hear “the leaves on my citrus are curled what do I do about it?!” Here again, one must definitely see the plant or large enough of a sample that accurately represents the problem.
When you walk into a nursery and ask someone what’s causing my citrus leaves to curl, you will almost always hear that the culprits are citrus leaf miners. Sure almost everyone in San Diego gets citrus leaf miners. But did you show them a sample of a curled leaf?
The two main pests that cause the leaves to curl on a citrus plant are (1) citrus leaf miners and (2) aphids. Both only attack the youngest leaves on growth tips. However, they are totally different from each other in how they feed on the plant and therefore how they make the leaves curl.
CITRUS LEAF MINERS are tiny little “chewing” insects that fly around and lay an egg on a young citrus leaf. When the egg hatches, the larva, eats the inside of the leaf which creates a tunnel (like a mining tunnel – hence, the name “leaf miner”). As the young leaf grows, the tunnels create scars that cause the leaves to curl as they develop and enlarge.
APHIDS, however, are tiny little “sucking” insects that poke microscopic holes in the youngest tissue of the growth tip, because young leaves and stems are the most tender. The aphids suck out the sugary photosynthate of the plant and secrete sticky goo called honeydew. The stickiness on your car after having been parked under a tree results from sucking insects in the tree (e.g. scale, mealybugs, aphids).
Look at these two photos of curled citrus leaves.
Damage resulting from citrus leaf miners; the “tunneling” causes leaves to curl randomly, where tunnels occur.
Lots damage from citrus leaf miners. This leaf is so damaged that will probably turn yellow and fall off later in the year.
Aphids are causing the new leaves to curl on this citrus plant. No tunnels are present and leaves are uniformly curling in a downward pattern.
Citrus Leaf Miners are chewing insects. “Spinosad” is an excellent, organic control for chewing insects. It comes in many forms like the Bonide brand Captain Jack’s Dead Bug. Alternatively one can use Citrus Leaf Miner pheromone traps.
Aphids, on the other hand, are sucking insects that require a different control. Try a Neem Oil-based product.
Organic bug controls breakdown quickly, and that’s a good thing. It also means that you will likely not get rid of all the bugs the first time, and that repeat applications will be necessary. See my previous blog on the difference between “chewing” and “sucking” insects.
Before using any controls, remember to read the entire instruction label, especially focusing on:
- When and when not to apply;
- How much to use;
- How often to reapply.
The purpose of this article is to enable you to correctly diagnose curled leaves on your citrus, and how to remedy the problem. If you are not 100% sure what your problem is after reading this article, have a specialist look at your citrus or take a large sample to a reputable, independent garden center for diagnosis.