Aphids (Green Peach, Cabbage, Cotton)
Myzus persicae; Brevicoryne brassicae; Aphis gossypii
Soft-bodied sap-sucking insects that cluster on shoots and leaf undersides. They transmit many plant viruses.
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Identify from a photoBackground
Several aphid species damage Australian vegetable gardens. The green peach aphid is the most common and also the most important virus vector. The grey-green waxy cabbage aphid specialises on brassicas. The cotton or melon aphid attacks cucurbits and many other families.
Aphids cause direct damage by sucking sap, leading to yellowing, curled or distorted leaves, and excrete sticky honeydew that grows sooty mould. Their greater significance, however, is as vectors of plant viruses such as cucumber mosaic, potato virus Y and tomato spotted wilt.
How to identify
- Green peach aphid: 1.5-2.5mm, pear-shaped, pale green to pink
- Cabbage aphid: greyish-green with a mealy white wax coating, clustered on brassica flowers and new growth
- Cotton/melon aphid: small (1-2mm), variable from pale yellow to dark green, on cucurbits and many other plants
- Damage: curled and yellowing leaves, stunted growth, sticky honeydew with black sooty mould
Life cycle
In Australia most aphid colonies reproduce parthenogenetically. Live young born already pregnant. A single female can found an entire colony in days. Winged forms appear when colonies get crowded or plants start to fail, spreading to new hosts.
Weather triggers
- Temperature: 10-30°C
- Populations build fastest in mild dry weather 18-25C. Heavy rain physically knocks colonies off plants.
Peak season (southern hemisphere)
Red = active season · Dark red outlined = this month
Affected vegetables & crops
Click any crop to see current prices and growing info.
Climate zones at risk
Organic & low-impact control
- A strong blast of water every few days dislodges colonies
- Soap sprays (potassium soap) or horticultural oil targeted at leaf undersides
- Encourage ladybird beetles, hoverflies and lacewings. Do not spray them out with broad-spectrum insecticides
- Pyrethrum for heavy outbreaks, applied at dusk
Chemical control
- Home garden systemic products containing imidacloprid work but are harmful to bees. Avoid on flowering crops
- Pirimicarb is selective for aphids and less damaging to beneficial insects (check current registrations)
Always read product labels. Registrations change.
Prevention
- Inspect new growth and leaf undersides weekly
- Remove and destroy the first colonies before winged forms develop
- Avoid excessive nitrogen fertiliser. Lush growth attracts aphids
Companion planting
Alyssum, dill, coriander, yarrow and buckwheat in flower attract hoverflies and parasitic wasps. Nasturtium is a trap crop for many aphids.
Biosecurity
Cosmopolitan pests, widely established.
Sources
- Agriculture Victoria, Aphids in vegetable crops: https://agriculture.vic.gov.au
- NSW DPI, Aphids as virus vectors
- CSIRO, Aphids of Australia
Accuracy confidence: high. We update this library as new extension guidance is published.
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