Lettuce inflorescence aphid

Acyrthosiphon lactucae

1. Identification

• Common name: Lettuce inflorescence aphid
• Scientific name: Acyrthosiphon lactucae Passerini
• Order: Hemiptera
• Family: Aphididae

2. Pest description

• Apterous adults: Elongated body; light green to yellowish-green colouring; long, cylindrical siphunculi; well-developed cauda.
• Alate adults: Darkened head and thorax; transparent wings; yellowish-green body; wing venation typical of the genus Acyrthosiphon.
• Nymphs: Similar to apterous adults, but smaller and of paler colouring.

3. Main hosts

• Species of the genus Lactuca (lettuce).
• Also recorded on Cichorium spp. and other wild Asteraceae.

4. Symptoms and damage

• Curling and deformation of young leaves.
• Reduced vigour and stunted growth.
• Excretion of honeydew, favouring the development of sooty mould.
• Potential to act as a vector of phytopathogenic viruses in horticultural crops.

5. Biological cycle

• Predominantly anholocyclic species in temperate regions.
• Reproduction by parthenogenesis during much of the year.
• Rapid development, with multiple generations per year.
• Populations increase in mild climates and under low pressure from beneficials.

6. Monitoring

• Direct observation of the underside of young leaves.
• Assessment of the presence of colonies and honeydew.
• Counting of individuals per plant to support decision-making in integrated protection.

7. Management measures

• Cultural: Removal of infested plants; control of wild host plants; management of planting density.
• Biological: Conservation of beneficials such as Coccinellidae, Syrphidae and parasitoids Aphidiinae.
• Integrated protection: Intervention only when population levels justify it; preference for selective methods compatible with beneficials.

Bibliographic references

• Blackman, R. L., & Eastop, V. F. (2000). Aphids on the World’s Crops: An Identification and Information Guide. Wiley.
• Blackman, R. L., & Eastop, V. F. (2006). Aphids on the World’s Herbaceous Plants and Shrubs. Wiley.
• van Emden, H. F., & Harrington, R. (2017). Aphids as Crop Pests (2nd ed.). CABI.
• Dixon, A. F. G. (1998). Aphid Ecology: An Optimization Approach. Chapman & Hall.