Lettuce Mosaic Virus
Lettuce mosaic virus (LMV), Potyvirus
Overview
A seed-borne virus of lettuce causing mosaic patterns, stunting, and reduced head formation. Transmitted by aphids and through infected seed. Lettuce Mosaic Virus cannot be cured with sprays. Management means preventing spread through insect vectors, infected seed or sap, and removing sources of inoculum early. Causal agent: Lettuce mosaic virus (LMV), Potyvirus. In regenerative gardens, prioritize sanitation, airflow, and unbroken soil cover over calendar spraying, and intervene early when symptoms appear.
Symptoms
Mosaic patterns of light and dark green on leaves. Leaf distortion and reduced size. Stunted growth. Poor head formation. Necrotic spots in some cultivars. Bolting. Compare several plants and note whether symptoms spread after rain, insect feeding, or wet foliage. Photograph undersides of leaves and cut stems when wilt is present to refine the diagnosis. Rule out simple drought, fertilizer burn, and herbicide drift before assuming a pathogen - abiotic injury often mimics disease.
Environmental Conditions
Variable
Prevention
Use virus-indexed seed (tested negative). Plant resistant varieties. Control aphid vectors. Remove weed hosts. Destroy crop residues. Mulch to reduce splash, clear season-end debris, and avoid working plants when wet. Design beds for airflow and diverse plantings that support beneficial insects without creating permanent humid pockets around susceptible crops.
Management
No cure. Remove infected plants. Use tested seed. Control aphids. Remove weed hosts including wild lettuce species. Prefer drip irrigation, morning watering, and open spacing so leaves dry quickly. Disinfect pruners between cuts on woody plants. Use copper, sulfur, or biological products only as labeled protectants when pressure is high - they rarely reverse advanced infections alone. Destroy (do not casually compost) highly infectious debris.