Potato psyllid
The potato psyllid, also called the tomato psyllid, is a tiny black-and-white insect, about 2–3 mm long, that looks like a miniature cicada and jumps when disturbed. It damages potatoes, tomatoes and peppers in two ways. The feeding nymphs inject a toxin that yellows and curls the top leaves and stunts the plant (psyllid yellows). The adults also carry the bacterium that causes zebra chip in potatoes. Once a plant is infected with the zebra chip bacterium it cannot be cured. There is no threshold, and biological control is not reliable in the field. Watch for the first arrivals on yellow sticky cards and act before a generation breeds on the plants.
Adult Bactericera cockerelli with its white abdominal band, beside scale-like nymphs and stalked eggs on a tomato leaf underside. Photo: pending.
Identification
Adults look like tiny cicadas. UC IPM gives about 0.08 inch (2 mm) on potato and about 0.12 inch (3 mm) on tomato. The clear wings are held rooflike over the body. The body is mostly black with white markings: a broad white band across the first abdominal segment and an inverted white 'V' on the last one. They jump readily when disturbed.
The nymphs are the stage to find. They are flat and oval, yellowish-green to orange, with red eyes and a fringe of short spines round the edge, and older ones have wing buds. They look like soft scale or whitefly nymphs, but move when disturbed; whitefly nymphs cannot. The football-shaped eggs sit on short stalks, mostly under the leaves along the edge and in the upper canopy. They are white at first, then yellow, and need a 10× lens to see.
Easily confused with
- Whitefly and soft scale nymphsAlso a pestPotato psyllid nymphs are flat and green with a fringe of short spines, and unlike whitefly nymphs they move readily when disturbed.
- Psocids (barklice)HarmlessAdult psyllids jump when disturbed and hold their wings rooflike; psocids run or fly off, and have a narrower neck and chewing mouthparts.
Damage symptoms
The two problems have different causes. Psyllid yellows is caused by the nymphs, which UC IPM suspects inject an as-yet unidentified toxin as they feed. As few as three or four nymphs per plant can produce symptoms, and removing the nymphs stops the disease getting worse. Zebra chip is a bacterial disease, Candidatus Liberibacter solanacearum, that the psyllid carries from plant to plant. It makes sugar build up in the tubers in place of starch, and the tubers fry with dark stripes. An infected plant cannot recover, and potatoes infected early can die within 3 weeks. The same bacterium is associated with yellows symptoms in tomato.
- Upward curling of the leaflets near the stem at the top of the plant
- Yellowing that starts at the leaf edges (purpling in some potato varieties)
- Rosettes of small leaves, short internodes and a dwarfed, pyramid-shaped plant
- Tomato transplants that die, or larger plants that set no fruit or many tiny ones
- Many small misshapen tubers, chain tubers or aerial tubers on potatoes
- Tubers with dark stripes, most obvious when fried (zebra chip); honeydew on the leaves
Lifecycle & degree days
In the West the potato psyllid used to be an occasional pest that flew in from Mexico in some years. UC IPM reports that a more invasive form now overwinters in California, so the psyllid turns up every year and has become a chronic problem there. In the Pacific Northwest the adults arrive in potato fields in late June or early July. In Texas they are on the plants from emergence. Eggs hatch in 4–15 days and the nymphs mature in 2–3 weeks, so generations overlap quickly in warm weather.
- Egg hatch
- 4–15 days
- Nymph to adult
- 5 instars in as little as 13 days (potato) or 2–3 weeks (tomato)
- Arrival
- From emergence in Texas; late June–early July in the Pacific Northwest
- Overwinters
- A more invasive form now overwinters in California; historically migrated from Mexico
Host crops
The psyllid feeds on many plants but prefers the nightshade family: tomatoes, potatoes, peppers and nightshade weeds. UC IPM notes a preference for the yellow pear tomato among tomato varieties. Potatoes suffer the most because they get both problems, the yellows toxin and the zebra chip bacterium. UC IPM calls for an area-wide approach that considers every host crop, tomatoes in particular: the psyllid moves between crops, so planting dates and which crops sit next to each other both matter.
Monitoring & action thresholds
UC IPM states there is no economic threshold for the potato psyllid in any North American crop. Most potato growers treat as soon as the first psyllids are found, because of the zebra chip risk. On tomato, UC IPM says a treatment may be warranted once adults are present. In a garden, the working rule is the same: do not let a generation complete its life cycle on the plants.
Hang yellow sticky cards at the edge of the planting, near the tops of the plants, to catch the first adults. Once one is caught, check the plants at the edges first, because psyllids colonise edges first. Turn over leaves in the top two-thirds of the plant and look for nymphs and stalked eggs with a hand lens; nymphs are easier to find than adults. UC IPM suggests examining 12–50 plants in a field, with 20 as the optimum; in a garden, check every plant at the edge.
Biological control
Biological control is weak outdoors. Spiders, lacewings and the parasitoid wasp Tamarixia triozae all attack the psyllid, but UC IPM notes that most parasites strike too late in the psyllid's life cycle to prevent crop loss. For field tomato it says biological control 'does not appear to be a promising control strategy'. Under glass the picture is better. In a greenhouse tomato trial by Koppert researchers, the predatory bug Dicyphus hesperus established and suppressed the psyllid, though the numbers left could still exceed tolerable levels; adding T. triozae gave better and more cost-effective control (Calvo et al. 2018). T. triozae is not profiled here yet. Outdoors, conserving predators still helps, and so does avoiding sprays that kill them.
Cultural controls
The garden levers are early detection and not making things worse. Carbamate sprays aimed at other pests actually increase psyllid numbers.
- Hang yellow sticky cards near the plant tops at the edge of the bed from planting
- Check leaf undersides in the upper canopy weekly for nymphs and stalked eggs
- Do not use carbaryl (Sevin) for other pests while psyllids are present; UC IPM says it promotes psyllid increase
- Clear nightshade weeds, which are preferred hosts, from around tomatoes and potatoes
- Where you can, avoid planting tomatoes right beside potatoes; UC IPM notes the psyllid moves between adjacent host crops
- Remove the nymphs early: psyllid yellows stops progressing when the immatures are removed
Chemical, last resort
- SpinosadREI 4 h
- SpirotetramatREI 24 h
- AbamectinREI 12 h
- Lambda-cyhalothrinREI 24 h
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
UC IPM Pest Management Guidelines: Potato — Potato Psyllid (Haviland & Trumble; text 04/2019)
UC IPM Pest Management Guidelines: Tomato — Tomato (Potato) Psyllid (text 12/2013)
UC IPM, Psyllids (Home and Landscape Pest Notes)
UC IPM, Relative Toxicities of Insecticides Used in Tomatoes to Natural Enemies (09/2016)
Calvo et al., J. Econ. Entomol. 111:549, 2018 — Dicyphus hesperus with Tamarixia triozae
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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