Dr. Phyto

lettuce

Lactuca sativa

Diseases & pests on this plant

• lettuce downy mildewBremia lactucae

  Yellow angular leaf spots bounded by veins (upper surface), corresponding white powdery sporulation on undersides in moist conditions, severe infection causes leaf collapse + crop loss, market quality lost from yellow patches alone, plants in greenhouses worst affected.

• lettuce aphidNasonovia ribisnigri

  Pale green-to-yellow aphids in heart of lettuce heads (the diagnostic location), heads with visible aphids unmarketable, sticky honeydew + sooty mould on lower leaves, severe infestations cause stunting + head deformation, virus transmission a secondary concern.

• slugs & snailsGastropoda

  Irregular holes with smooth (not jagged) edges eaten from leaves, flowers and soft stems, often starting at the margins; whole seedlings can vanish overnight; tender hostas, lettuces and bedding are stripped; the tell-tale sign is a silvery dried slime trail on leaves, soil and pots. Damage is worst at night and in mild, wet weather.

• sclerotinia stem rotSclerotinia sclerotiorum

  White cottony growth on stems at flowering height, stems split open to show black sclerotia (1–5 mm) embedded in pith, premature ripening of affected plants.

• Lettuce mosaic virus (LMV)Lettuce mosaic virus

  Yellow mosaic patterns on leaves, distorted + crinkled leaf shape, stunting + reduced head formation, plants infected early in growth fail to form marketable heads, virus persists in some weed species + carried in seed if not certified.