Identify the crop and the aphid

Inspect ears and upper leaves for grain aphids, and leaf undersides for rose-grain aphids.

Resistance-test findings apply to the species sampled, so identify the aphid before you choose an aphid insecticide spray.

Understand feeding damage and virus risk separately

Young cereal plants are particularly susceptible to BYDV. Look for yellowing leaf tips and clusters of stunted plants.

Aphid species in cereals and horticultural crops

Bird cherry-oat, grain, rose-grain, blackberry and fescue aphids occur in Northern Ireland cereals. Follow population trends before deciding whether intervention is needed.

Aphid species by scientific name

Horticultural species include peach-potato aphid, Myzus persicae; potato aphid, Macrosiphum euphorbiae; currant-lettuce aphid, Nasonovia ribisnigri; and willow-carrot aphid, Cavariella aegopodii. Cereal examples include grain aphid, Sitobion avenae; bird cherry-oat aphid, Rhopalosiphum padi; and rose-grain aphid, Metopolophium dirhodum.

Use trap information as monitoring evidence

Suction-trap catches track aphid migration and species abundance. AFBI's dashboard supplies activity trends for Northern Ireland. Use trap data together with crop surveys and evidence about virus-carrying aphids.

Weather and natural enemies can reduce aphid populations substantially. Check whether numbers are rising or falling before choosing a treatment.

Sowing date and the green bridge

Early-sown winter crops stay exposed for longer to migrating aphids such as the bird cherry-oat aphid. Cereals that follow grass are also at risk from the green bridge, where aphids move from grass and weeds into the emerging crop. Sowing time and preceding vegetation matter for BYDV prevention.

Woolly aphid on apple trees: control first, then a pesticide for woolly aphids

Woolly aphid (American blight, Eriosoma lanigerum) is common on edible apple trees, pyracantha and Cotoneaster horizontalis; its white waxy fluff can be mistaken for fungal growth. Tolerate populations where possible, check trees from spring so that action is taken before a damaging population builds up, squash colonies with finger and thumb where practical, and encourage predators such as ladybirds, hoverflies, parasitoid wasps and earwigs; natural enemies normally reduce numbers by late summer. A pesticide for woolly aphids is therefore a second step: choose a product only if its label lists the crop and the pest, and find it through the HSE register guide.

Resistance tests: bioassays and DNA diagnostics

Live-insect bioassays measure reduced sensitivity to insecticides without first identifying the exact mechanism of resistance. DNA diagnostics detect mutations associated with established resistance traits.

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Insecticide for aphids: the product label decides

The product label sets the crop or situation, individual dose, repeat-treatment limits, timing and protection conditions. For the best insecticide or pesticide for potatoes, the identified pest decides first and the label sets the potato use.

For an aphid intervention in Great Britain, Article 55(2) includes compliance with the authorised conditions specified on the labelling within proper use.

Aphid resistance screening

ADAS screening within a Defra-funded project covers peach-potato, bird cherry-oat and grain aphids, plus cabbage stem flea beetle. The sampling invitation was published on 22 January 2026.

Combine crop, virus and economic inputs

For winter-cereal BYDV decisions, assess aphid population dynamics, virus spread and the economics of intervention. The inputs are drill date, aphid pressure, the proportion carrying virus, varietal tolerance and crop economics.

Distinguish resistance of a crop variety or its tolerance to disease from resistance of an insect to an insecticide. The former concerns the crop's response; the latter concerns the pest's sensitivity.

Potato aphid identification

The potato aphid is Macrosiphum euphorbiae. Wingless forms have long legs and antennae. Heavy feeding can produce false top roll, while natural enemies may fail to prevent virus transmission even where they suppress aphid populations.

For potato aphid, no numerical treatment threshold is established. Consider treatment when numbers increase rapidly on varieties susceptible to false top roll. Wingless adults are 2.5–4 mm long, with green to pinkish-red bodies, red eyes and a dark stripe along the back.

Aphids on potato plants and other hosts

Identify aphids on potato plants by species, then assess feeding damage and virus risk. Potato aphids overwinter on weeds, potato sprouts, roses and protected lettuce, and feed and reproduce on summer crops from May to October.

Potato aphid life cycle and virus symptoms

Winged forms migrate to summer crops in May and June. Heavy infestation can prompt another migration in July, with a smaller autumn movement possible in September.

Potato virus Y can produce black streaks beneath lower-leaf veins, followed by collapse and leaves hanging from the stem. Younger leaves may develop necrotic spots. Potato leafroll virus produces upward and inward rolling at young leaflet margins, sometimes with purple discolouration. False top roll caused by heavy aphid feeding appears in distinct patches with aphids or cast skins present.

Inspect natural enemies alongside the colony: parasitic wasps, ladybirds, predatory flies, spiders, ground and rove beetles, lacewings and insect-pathogenic fungi contribute to population control. Virus transmission can occur at low aphid densities, so assess that risk separately from colony size.

Next step

Use the IPM assessment to weigh species, crop susceptibility and population trends, and the HSE register guide to find a product label.