Asian citrus psyllid
A mottled-brown psyllid 1/8 to 1/6 inch (3–4 mm) long that breeds only on the soft new growth of citrus and a few relatives such as orange jasmine and curry leaf. Its feeding twists and notches young leaves, which UC IPM says trees can tolerate, though killed shoots set back young trees. The danger is that it spreads huanglongbing (HLB, or citrus greening), a bacterial disease with no cure that UC IPM says can kill a tree in as little as five years. Where it is under quarantine, do not move citrus plants or clippings, and report suspected finds to your state department of agriculture.
Adult Diaphorina citri in its tilted, head-down feeding posture on a young citrus leaf. Photo: pending.
Identification
Adults are 3–4 mm (1/8 to 1/6 inch) long, with a mottled brown body, a light brown head, red eyes and short antennae, and often look dusty with white wax. The brown band along the edge of the wing is broken by a clear stripe. The surest tell is the posture: the adult feeds with its head down, almost touching the leaf, and its body raised at an angle: about 45° according to UC IPM, closer to 30° according to UF/IFAS. UC IPM notes that no other insect pest of citrus holds itself this way.
The eggs are tiny, yellow-orange and almond-shaped, tucked into the folds of unopened leaves. Nymphs are yellow-orange to brownish, flat and wingless, and grow from 0.25 mm to about 1.5–1.7 mm through five instars; they stay on tender shoots and cannot fly. Each nymph trails a waxy tubule from its rear, and a curly tube with a bulb at the end is unique to this psyllid. A hand lens makes all of this far easier to see.
Easily confused with
- Potato (tomato) psyllidAlso a pestUC IPM names tomato psyllid among the psyllids ACP is confused with. Only ACP has the brown wing edge broken by a clear stripe and the steep head-down feeding tilt, and only its nymphs make curly wax tubules with a bulb.
- Eucalyptus and eugenia psyllidsAlso a pestUC IPM lists them among the psyllids mistaken for ACP. Only ACP has the brown wing edge broken by a clear stripe and the steep head-down feeding tilt, and only its nymphs trail curly wax tubules with a bulb.
Damage symptoms
The psyllid's own damage is modest. Nymphs inject a toxin as they feed that twists and curls the new leaves, and can stunt or kill the shoot; when the leaf matures it keeps a characteristic notch. Honeydew leads to sooty mould, which UC IPM calls unsightly but not harmful. The serious harm is disease. The psyllid spreads the bacterium Candidatus Liberibacter asiaticus, which causes huanglongbing. UC IPM says symptoms may not show for two or more years after infection, and that an infected tree can die in as little as five years.
- Twisted, curled new leaves that keep a notch as they mature
- Stunted or dead new shoots after heavy feeding by nymphs
- White wax tubules and sticky honeydew on new flush, then black sooty mould
- HLB: blotchy yellow mottling that differs on either side of the midrib, often on one limb first
- HLB: small, lopsided, bitter fruit with aborted seeds that drops early, and twig dieback
Lifecycle & degree days
Everything depends on new growth. Females lay only on flush, the soft leaves at the tips of shoots, and the nymphs cannot survive on hardened leaves. Mature trees flush mostly in spring and autumn, while young trees and lemons flush on and off all year in warm weather, which keeps the psyllid breeding. In a Southern California residential study, numbers were highest from July through November and rose with temperature. Extreme heat slows it: UC IPM says development slows at 104 °F (40 °C), and three or more hours a day at 108 °F (42.2 °C) kills nymphs. The figures below come from Florida (Mead and Fasulo, UF/IFAS) and UC IPM.
- Egg to adult
- 15–47 days, by season (UF/IFAS); a generation takes about 3 weeks (UC IPM)
- Eggs per female
- Several hundred (UC IPM); more than 800 (UF/IFAS)
- Generations / yr
- 9–10 in Florida; 16 seen in field cages
- Adult lifespan
- 1–2 months (UC IPM); several months (UF/IFAS)
Host crops
Only plants in the citrus family, Rutaceae: all common citrus, plus relatives such as calamondin, box orange, orange jasmine (Murraya paniculata) and Indian curry leaf. Orange jasmine and curry leaf are ornamentals that people forget are hosts, and a Southern California study found the most adult psyllids on curry leaf. HLB affects orange jasmine as well as citrus.
Monitoring & action thresholds
Outside a known infested area, a single find matters: report it (in California, the CDFA hotline is 1-800-491-1899) and the quarantine may be extended. Where the psyllid is already established, UC IPM advises treating only when psyllids have been seen. The only published numeric threshold is commercial: any life stage on 2 or more flushes out of 10 sampled (UC IPM citrus guidelines).
Check citrus monthly from spring through autumn, and whenever the tree is putting out new growth. Look at the young flush with a hand lens for yellow eggs in the leaf folds, nymphs with their curly wax tubules, and adults tilted head-down on the leaves. The eggs and nymphs cannot fly, so they are the stages to look for. Watch too for leaves yellowing unevenly on one limb, which can be HLB, and report it straight away.
Biological control
The main biological control is a tiny parasitic wasp, Tamarixia radiata, collected from the psyllid's native range. It lays eggs on older nymphs and turns them into hollow, darkened 'mummies' with an exit hole. In California it is reared and released by the state (CDFA), which reports releasing more than 34 million across the state, targeting residential areas where the psyllid is known; the sources we checked describe no way for gardeners to buy it. The results are real but partial. The UC IPM citrus guidelines report parasitism as high as 70% where it has established, but a 2012–2014 study of Southern California yards averaged under 5%, and UC IPM says it has not stopped the spread of HLB. Wild predators also eat psyllids: lady beetles, hoverfly larvae, lacewing larvae, minute pirate bugs and spiders. The UC IPM citrus guidelines name hoverfly larvae as the key predators of the nymphs, but find little field evidence that lady beetles, lacewings or spiders give significant control. Argentine ants farm the psyllid's honeydew and drive these enemies off, so ant control is part of the job.
Cultural controls
For a home citrus tree, the priorities are keeping the psyllid and HLB out, and reporting what you find. Sprays come after that, and only where the psyllid is already known.
- Buy citrus from reputable local nurseries; APHIS asks buyers to use only USDA-certified plants
- Never move citrus plants, branches, clippings or green waste out of a quarantine area
- Check before moving home-grown fruit: APHIS says keep it in the quarantine area; UC IPM says California allows washed fruit free of leaves and stems
- Report suspected psyllids or blotchy, uneven yellowing to your state plant agency
- Control ants on the trunk so parasitoids and predators can work
- Check new flush monthly with a hand lens, when the tree is putting out new growth
Chemical, last resort
- Narrow-range (horticultural) oilREI per label
- SpinosadREI 4 h
- PyrethrinsREI 12 h
- Imidacloprid (soil drench)REI 12 h
- Beta-cyfluthrinREI 12 h
Sources
UC IPM Pest Notes 74155, Asian Citrus Psyllid and Huanglongbing (Grafton-Cardwell & Daugherty, 2018)
UC IPM Pest Management Guidelines: Citrus — Asian Citrus Psyllid (11/2024)
UC IPM Citrus Guidelines, Selectivity of Insecticides and Miticides (06/2022)
UF/IFAS EDIS IN160 (Featured Creatures EENY-033), Asian Citrus Psyllid (Mead & Fasulo)
USDA APHIS, Citrus Greening and Asian Citrus Psyllid (updated 04/2026)
CDFA Citrus Pest and Disease Prevention Division: ACP quarantine; Tamarixia biocontrol
Kistner et al., Phenology of ACP in Southern California residences, J. Econ. Entomol. 2016
Vankosky & Hoddle, Competition between two ACP parasitoids, Insect Sci. 2019
California Citrus Threat (CDFA): HLB hosts; Tamarixia releases
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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