Three Real Sources of Aphid Infestation
Infested planting material — quarantine for 7–10 days with thorough inspection before introducing plants to the growing area.
Winged forms — when a colony becomes overcrowded, winged aphids develop and migrate through damaged ventilation screens.
Ants as carriers — ants feed on honeydew, protect aphid colonies from natural enemies, and spread populations to other plants.
Why Aphids Are Dangerous
- Honeydew → sooty mould → reduced photosynthesis
- Virus transmission — aphids are the primary vector for cucumber mosaic virus and potato virus Y
Control
Monitoring: inspect shoot tips and young leaves regularly. One week's delay equals a population in the thousands.
Mechanical removal: small, localised colonies can be removed by hand.
Biological control:
- Aphidius colemani — parasitic wasp that creates mummified aphids
- Aphidoletes aphidimyza — predatory midge effective at higher aphid densities
Beneficial insects do not work effectively when ants are present.
Chemical control: systemic products (flonicamid, pirimiphos-methyl) or contact products with IRAC group rotation.
Three Mistakes That Cost the Most
- Ignoring ants — they drive off beneficials and introduce new aphids
- Waiting for numbers to grow — at 5–10 individuals, action is already required
- Pyrethroids as the first line of defence — most aphid populations carry resistance
Signs of Successful Control
- Two weeks of inspections with no new colonies
- Mummified aphids present (indicating parasitic wasp activity)
- No new honeydew deposits
- Ants absent or physically excluded from plants