Leafminer

Liriomyza spp.

1. Identification

• Common name: Leafminer
• Scientific name: Liriomyza spp. (includes L. trifolii Burgess, L. huidobrensis Blanchard, L. sativae Blanchard)
• Order: Diptera
• Family: Agromyzidae

2. Pest description

• Adults: Small flies of 1.5–2.5 mm, yellowish-grey body, dark thorax and yellowish abdomen; very mobile.
• Larvae: Apodous, whitish to yellow, they develop inside the leaves forming winding mines.
• Pupae: Usually in the soil, but they may occur on the leaf itself.
• Eggs: Laid individually in the leaf tissue, leaving small visible punctures.

3. Main hosts

• Vegetables: tomato, bean, cucumber, melon, lettuce, celery, potato.
• Ornamentals: chrysanthemum, gerbera, gypsophila, among many others.
• Highly polyphagous species, with dozens of hosts.

4. Symptoms and damage

• Winding mines in the leaf blade, initially narrow and then widening.
• Feeding punctures of adults on the leaf surface.
• Reduction of the photosynthetic area and yellowing.
• Premature leaf drop in severe attacks.
• In vegetable crops, production losses and reduction of commercial quality.

5. Biological cycle

• Fast cycle, which can be completed in 2–3 weeks under favourable conditions.
• Adults live 1–2 weeks, feeding and ovipositing actively.
• Larvae develop inside the leaf for 4–7 days.
• Pupation mostly in the soil; adults emerge after 7–14 days.
• Development favoured by high temperatures and high host density.

6. Monitoring

• Direct observation of fresh mines and oviposition punctures.
• Counting of live larvae inside the mines.
• Yellow chromotropic traps for detection of adults.
• Reinforced monitoring in greenhouses and warm periods.

7. Management measures

• Cultural: Removal of heavily infested leaves; elimination of crop residues; avoid excess nitrogen fertilisation; adequate ventilation in greenhouses; avoid proximity to highly susceptible ornamental plants.
• Biological: Use of authorised entomopathogenic microorganisms; application of microbial bioinsecticides; conservation of native parasitoids through appropriate cultural practices.
• Integrated protection: Regular monitoring; intervention only when necessary; practices that reduce the survival of larvae in the leaves and the emergence of adults.

Bibliographic references

• EPPO Global Database – Liriomyza spp.
• CABI Invasive Species Compendium – Liriomyza trifolii, L. huidobrensis, L. sativae
• Parrella, M. P. (1987). Biology of Liriomyza spp. Annual Review of Entomology, 32: 201–224.
• Weintraub, P. G. (2001). Changes in the host range of Liriomyza huidobrensis. Crop Protection, 20: 783–788.
• Spencer, K. A. (1973). Agromyzidae (Diptera) of Economic Importance. Dr. W. Junk Publishers.