Pests in Gardens and Landscapes: Quick Tips
Asian Citrus Psyllid and Huanglongbing Disease
Brownish adult, yellow nymphs, and white wax of Asian citrus psyllids (left).
Symptoms of HLB on leaves and fruit (right).
Yellowish nymphs of Asian citrus psyllid with red eyes and white waxy tubules.
The Asian citrus psyllid and the deadly bacterial disease it spreads, Huanglongbing (HLB), threaten citrus trees in backyards and on farms. The psyllid arrived in Southern California in 2008, and HLB disease was first detected in Los Angeles in 2012. All types of citrus—including oranges, grapefruit, lemons, and mandarins—are affected as well as a few closely related ornamentals.
What are some of the concerns?
- The Asian citrus psyllid carries HLB disease from tree to tree.
- HLB disease will kill trees in as little as five years.
- There is no cure or effective control method for HLB disease.
Inspect your citrus trees for psyllids.
- Reducing the psyllid population helps to slow the spread of HLB disease.
- From spring through fall, look for psyllid eggs, nymphs, and adults on newly forming leaves.
- Adults are about the size of an aphid and have brownish mottled wings. They feed with their head down and their “tail” in the air.
- Nymphs are tiny and yellowish, and they excrete white waxy tubules.
- Psyllids feed on plant sap and produce sticky honeydew that may be covered with black sooty mold. However, other citrus pests (e.g., aphids and soft scales) may cause this symptom too.
- Although this psyllid can damage leaves, it doesn’t kill trees by itself, and fruit is safe to eat.
What are the symptoms of HLB disease?
- Leaves show an asymmetrical yellow mottling with patches of green.
- Fruit are small, lopsided, and fall off the tree easily, and the juice tastes bitter.
What should you do if you think you have the Asian citrus psyllid or HLB disease?
- Contact your agricultural commissioner’s office, or call the California Department of Food and Agriculture (CDFA) Exotic Pest Hotline at 1-800-491-1899 to confirm a find.
How can I manage the psyllid and disease?
- Plant trees from reputable nurseries to avoid bringing either the insect or HLB into your yard.
- Check your trees monthly, especially the newly forming leaves psyllids prefer to live on.
- Parasitic wasps that attack Asian citrus psyllids have been released in some areas. These wasps will help to reduce psyllid numbers but aren’t likely to stop the spread of HLB disease.
- You can reduce psyllid numbers by treating infested trees with insecticides including oils, soaps, carbaryl, or systemic imidacloprid. Oils and soaps don’t last long, so they need to be reapplied every few weeks. Carbaryl and imidacloprid are longer lasting, but because both are toxic to bees, don’t use these products when citrus are in bloom. Make sure foliar-applied insecticides reach the new growth where young psyllids hide.
- Learn where you are relative to quarantines. Don’t move plants or clippings out of infested areas, because doing so can spread the insect and disease.
- Because there are currently no cures for HLB disease, diseased trees must be removed to protect the trees around them from becoming infected.
Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.