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An Asian Citrus Psyllid sits on a leaf while a fingertip in the top left corner shows just how small the insect is.
A cluster of 8 yellow, semi-translucent eggs sit on a narrow green leaf.
Dorsal view of 5 nymph stages ranging smallest to largest from left to right of the Asian Citrus Psyllid.
Closeup side view of an Asian Citrus Psyllid sitting on a green branch surrounded by leaves.
Side view of the Asian Citrus Psyllid with outstretched legs.
Dorsal view of the Asian Citrus Psyllid.
Extreme closeup profile of the head of the Asian Citrus Psyllid
The side view of an Asian Citrus Psyllid agains a light blue background.

Asian Citrus Psyllid

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What is it

The Citrus Psyllid is an insect that feeds on the leaves and stems of citrus trees, and the Asian variety (Diaphorina citri, ACP) is a threat to citrus crops in the U.S. The adult ACP is very small (usually 2-4 millimeters) and is typically mottled brown in color. Pregnant females and nymphs (juveniles) are yellowish orange, and nymphs have bright red eyes. Adults are often found feeding on the underside of leaves, but the nymphs feed only on new growth. The ACP eggs are yellow in color and are usually found on the newest growth, tucked in the folds of new leaves.

How does it cause harm?

The adult ACP feeds on the sap of leaves and twigs of citrus trees (including orange, lemon, lime, mandarin, pomello, kumquat, grapefruit and tangerine) producing sticky honeydew, which can cause the leaves to mold. Nymphs are equally dangerous to young plants as they feed only on new growth and can cause leaves to grow misshapen and deformed. Excessive feeding can cause leaf buds to die preventing leaves from forming. Established plants can survive the nymphs feeding, but young plants often die before they can establish healthy leaf growth.

Though excessive feeding and development of mold can kill citrus trees, a more serious problem is related to Huanglongbing (HLB) or citrus greening disease. It is one of the deadliest citrus diseases in the world and has only one natural carrier for spreading the infection, the Citrus Psyllid.

What is Huanglongbing (HLB)?

HLB is a bacterial infection that infects citrus trees and is always fatal. Diseased trees produce hard, bitter, and misshapen fruit, the leaves turn a mottled yellow color, and twigs begin to die. Trees infected with HLB lose their value as fruit-bearing trees and die in as little as five years. There is no cure for HLB, and rapid removal of infected trees is vital to preventing the spread of the disease.

How do we stop it?

Because there is no cure for HLB, early detection is the key to preventing the spread of the disease. Nursery workers within the federal quarantine must screen for the Asian Citrus Psyllid and look for symptoms of HLB, and homeowners are encouraged to inspect their citrus trees and report any infestations. Efforts are underway to find other insect species that prey on the ACP, the most promising of which is the Tamarixia radiate, a tiny parasitic wasp. Chemical treatments, such as insecticidal soaps and sprays are effective at killing off the adults and nymphs but only last a few days to a few weeks and must be repeated regularly. To date, the most effective means of protecting citrus trees from HLB is limit the spread of the ACP.