BioWiki / Pests

Aphids

tags: - public-ready - export-bio

Aphids

Overview

Aphids multiply rapidly on soft growth and can cause distortion, honeydew, and virus spread.

Symptoms

  • Leaf curl / distortion
  • Sticky honeydew / sooty mould
  • Colonies on shoots/undersides

Conditions that increase risk

Biological control options

IPM notes

  • Monitoring & Thresholds
  • Avoid disruption: Avoid Broad Spectrum Sprays

Further guidance

  • Aphids — Biocontrol Foundations

Key UK aphid species

  • Aphids — Uk Commercial Species Index

Key natural enemies

Environmental drivers

  • Rapid build-up in mild to warm conditions when plants are pushing soft growth.
  • Plant stress (e.g., heat/water stress) can increase susceptibility and reduce tolerance.
  • Natural enemy activity can lag behind aphid growth during fast crop flushes.

Thermal Overlap Example — Aphids × Parasitoids (Aphidius spp.)

Aphids (Generalised Thermal Behaviour)

  • Low developmental threshold (~4–8°C species dependent)
  • Rapid multiplication in moderate warmth (18–25°C)
  • Parthenogenetic reproduction enables exponential increase
  • Consecutive mild nights accelerate population growth

Aphidius spp. (Conceptual Thermal Behaviour)

  • Active in moderate warmth
  • Optimal parasitism typically 18–25°C
  • Reduced efficiency in extreme heat
  • Parasitism rate temperature dependent

Overlap Analysis

Mild–moderate temperatures (18–23°C): Strong thermal overlap. High suppression potential.

Warm spells (25–30°C): Aphid reproduction accelerates. Parasitoid performance may plateau. Lag window narrows.

Heat stress conditions: Risk of Rp − Rd widening.

Ecological Insight

Aphid outbreaks in warm springs are often:

Temperature-driven
before they are visibly count-driven.

Parasitoids require:

Time
Host density
Favourable thermal conditions

to respond effectively.

See: - Thermal Overlap Risk Model - Predator–Pest Ratio Modelling - Intervention Decision Logic — Act Or Hold

Risk Index Scoring (Aphids)

For structured scoring see: - Aphids — Risk Index Calibration (V1)

Consider: - Warm nights as acceleration trigger - Colony expansion speed - Mummy ratio trend - Crop sensitivity window

IPM Risk Engine Integration

Aphids are classified in the IPM Risk Engine as:

Nutrient Surge Responders

See: - Ipm Risk Engine Hub - Ipm Risk Engine — Protected Crops

Risk escalates during soft vegetative flush and nitrogen-driven growth.