Identification
Small sucking insects whose adults resemble tiny cicadas and jump off the shoots when disturbed. The flat, yellowish nymphs feed on the shoots, leaves and fruit of the pear, excreting abundant sticky honeydew. Sooty mould develops on the honeydew, coating and blackening the leaves, shoots and fruit, weakening the plant and leaving the fruit deformed and soiled. The pear psylla is also a vector of the dangerous pear decline (phytoplasma), which makes it particularly harmful. The adults are 2.5-3 mm long with roof-like folded wings, and they occur in two seasonal forms - a larger, dark (brownish-black) winter form that overwinters, and a smaller, paler yellow-green summer form that develops in the warmer months. The eggs are small and elongate, at first yellowish then orange, laid in chains along the shoots, at the base of the buds and on the spurs. The newly hatched nymphs are flattened and oval, sitting in a droplet of their own honeydew, darkening with age and developing wing buds. Several overlapping generations (usually 3-5) develop over the season. The insect overwinters as the adult winter form in bark crevices, under flaking bark and in the leaf litter in the orchard and its surroundings; the females lay their first eggs very early, before budburst, on the bare shoots. Under heavy infestation the leaves drop prematurely, growth is weak, and the fruit is russeted and soiled by the sooty mould.
Treatment
Early-spring sprays of paraffin oils reduce eggs and young nymphs before the population builds up. Potassium soap, which washes off the nymphs, and rinsing the honeydew away with a strong jet of water both help. The key is to protect and encourage natural enemies - anthocorid bugs (Anthocoris), lacewings and other predators, which effectively keep the pear psylla in check in a balanced orchard. Decisions rest on monitoring: shaking the shoots over a light-coloured tray and inspecting the buds for egg clusters allow the treatment date to be timed accurately, because control is most effective against the youngest larval stages. A kaolin clay coating applied in early spring discourages the females from laying eggs and makes feeding harder for the nymphs. It is worth limiting excessive nitrogen fertilisation, because lush, sappy growth favours the pear psylla, and maintaining winter orchard hygiene. Broad-spectrum insecticides, especially pyrethroids, should be avoided - they wipe out natural enemies, trigger a rapid rebound of the pear psylla population and accelerate the build-up of resistance. Once the damage threshold is exceeded, the most selective products possible are used, for example insect growth regulators (IGRs) acting on the larvae, rotating the modes of action to delay resistance.
How to tell it apart from look-alikes
| Feature | Pear psylla | Aphids |
|---|---|---|
| Insect appearance | Flat, yellow-green nymphs sitting in a droplet of honeydew; adults shaped like a small cicada, without siphunculi. | Pear-shaped insects with a pair of siphunculi (tubes) at the end of the abdomen, feeding in dense colonies. |
| Reaction to shaking | Adults jump and spring off the shoot (hence 'jumping plant louse'). | Sluggish, do not jump - they stay on the leaf or shoot. |
| Symptom on the leaf | Leaves coated with honeydew and sooty mould, usually without typical curling. | Often strong twisting, rolling and deformation of the leaves (e.g. Dysaphis pyri). |
| Host range | Pear only. | Very wide - many plant species, often with a host change during the season. |
| Importance as a vector | Transmits pear decline (phytoplasma) - a dangerous disease. | Less significant on pear; some species transmit viruses of other plants. |
Control — organic and chemical methods
Organic and biological methods
| Method | How it works | When to use |
|---|---|---|
| Paraffin/mineral oils | Coat the eggs and young nymphs with an oil film, smothering them and discouraging the females from laying eggs on the shoots. | Early spring, from bud swell, before the first generation develops. |
| Protecting natural enemies | Anthocoris flower bugs, lacewings, ladybirds and earwigs eat the eggs and nymphs, keeping the population below the threshold. | All season; protect them by limiting broad-spectrum sprays. |
| Kaolin clay (particle film) | A white mineral film on the shoots deters the females from laying eggs and makes feeding harder for the nymphs. | Preventively in early spring; renew after rains wash off the coating. |
| Potassium soap and washing off honeydew with water | The soap washes off and desiccates the nymphs, while a strong jet of water rinses away the sticky honeydew that fuels the sooty mould. | As a supporting measure at low intensity; requires repetition. |
Chemical methods
| Method | How it works | When to use |
|---|---|---|
| Insect growth regulators (IGRs) | They disrupt the moulting and development of the larvae, checking successive generations, while sparing some of the beneficial predators. | After the threshold is exceeded, targeting the youngest larvae, with rotation of the modes of action. |
We give active-ingredient groups and modes of action, not brand names — specific products and their approval vary by country and are sometimes withdrawn. Always check and follow the current label.
Sources
- Orchard plant protection programme
- Institute of Horticulture in Skierniewice
