Pest & Disease | Citrus Insider

Asian Citrus Psyllid & Huanglongbing

The Pest

The Asian citrus psyllid is an aphid-sized pest that arrived in California in 2008 and has since infested parts of Southern California. The pest itself can be managed with an integrated pest management approach of insecticides and natural enemies; however, the real danger lies in the psyllid’s ability to transmit a bacterium that causes Huanglongbing, a deadly and incurable plant disease. For this reason, identification and control of the psyllid is essential.

The Disease

Huanglongbing (HLB) – also known as citrus greening disease – is a death sentence for California citrus. It is caused by a bacterium that can be transmitted by the Asian citrus psyllid or by grafting infected plant material. HLB symptoms in citrus trees include asymmetrical, blotchy yellowing of leaves, small asymmetrical fruit with bitter juice that easily falls off of the tree and eventually leads to tree death. HLB has been detected in Southern California in parts of Orange, Los Angeles, Riverside and San Bernardino Counties. Citrus trees throughout the state are in danger. While researchers are working diligently on a solution, it is essential to control the psyllid so it doesn’t spread the disease.

For more information on psyllids, the disease, best practices and treatment options, visit the Psyllid & Disease section.

  • Photo of Asian citrus psyllid adults and nymphs

    Asian citrus psyllids feed on citrus leaves and stems, and can infect trees with deadly Huanglongbing disease. Seen here are adults and young nymphs.

  • How to find the Asian citrus psyllid on citrus leaves

    Inspect for Asian citrus psyllids monthly. Look for small, brown pests that feed on citrus leaves with their body at a 45-degree angle.

  • Inspect citrus tree flush for the Asian citrus psyllid pest

    Check new flush, the smallest, tender new leaves sprouting on your citrus tree, for the Asian citrus psyllid. This is a favorite spot for the pest to feed and lay eggs.

  • Asian citrus psyllid nymphs produce a white secretion on tree leaves

    Young Asian citrus psyllids, called nymphs, produce a white, waxy substance to direct honeydew away from their bodies.

  • Adult Asian citrus psyllid photo

    Asian citrus psyllids are small – no more than 1/8th of an inch long – brown, winged insects that feed on citrus tree leaves and stems.

  • Citrus tree sooty mold from Asian citrus psyllid

    Asian citrus psyllids can cause a sooty mold to form on citrus tree leaves.

  • Twisted leaf damage on citrus trees

    When Asian citrus psyllids feed on citrus tree leaves, they can cause a twisting damage to the leaf.

  • Ants and Asian citrus psyllid on tree leaf

    Ants actually protect Asian citrus psyllid nymphs, therefore it is important to apply ant bait around your tree.

  • Asymmetrical yellowing from Huanglongbing disease

    A symptom of Huanglongbing is yellow discoloration on leaves that is asymmetrical, meaning not the same on both sides of the leaf.

  • Huanglongbing causing yellow leaves on citrus tree

    Huanglongbing causes uneven yellowing in citrus tree leaves because nutrients are being restricted.

  • Citrus tree leaves turning yellow from Huanglongbing disease

    This blotchy yellowing of citrus tree leaves is an early sign of Huanglongbing and will worsen as the disease develops in the tree.

  • Pomello tree infected with Huanglongbing

    Huanglongbing seen here in a pomello tree. All varieties of citrus are at risk of contracting and dying from the disease.

  • Citrus greening disease shown on fruit

    Huanglongbing is also known as citrus greening disease because it causes fruit to stay green and not fully ripen.

  • Yellow shoots on citrus trees

    In Asia, Huanglongbing is sometimes known as yellow dragon disease due to the symptoms of entire shoots turning yellow.

  • Misshapen citrus fruit due to Huanglongbing

    Citrus fruit from trees infected with Huanglongbing may be misshapen and lose their symmetrical appearance.

  • Corky vein symptom of Huanglongbing

    Corky veins on citrus tree leaves is another symptom of Huanglongbing.

  • Citrus greening disease in Florida groves

    Huanglongbing, also known as citrus greening disease, has decimated citrus groves in Florida. We must protect California citrus trees from this threat.

  • Grafting citrus tree

    When grafting citrus fruit varieties, it is important to get registered budwood from a reputable source to avoid grafting plant material infected with Huanglongbing to your healthy tree.

  • Removing citrus tree infected with Huanglongbing

    It is important to remove diseased trees to prevent Huanglongbing from spreading to healthy citrus trees nearby.

  • Yellow pest traps placed in citrus trees

    Agriculture officials track the presence of pests like the Asian citrus psyllid by placing yellow sticky traps in citrus trees throughout the state. When you allow these traps on your property, you help protect California citrus.