Lettuce

Slugs and snails

What you will see

Irregular holes in soft leaves and young shoots and slime trails; they feed at night.

The source says: it is among the plants that slugs and snails seriously damage.

How to protect

1. Prevention

   • Plant sturdy potted plants, not delicate young seedlings.
   • Water in the morning, not the evening (evening watering helps them move around).
   • Encourage their natural enemies: birds, hedgehogs, toads, ground beetles.
2. By hand evening, after rainPick them off by hand on damp evenings and take them far away. Traps: hollowed-out citrus halves placed cut side down, or sunken containers of beer; check in the morning.
3. Biological when the soil is warm and moistSlug-specific nematodes (from a biological control supplier) are watered into the soil.
4. Chemical — only when nothing else helps according to the product labelLast resort only: a product authorised in your country against slugs and snails. Try non-chemical methods first.

Lettuce downy mildew

What you will see

Yellow patches on leaves and a white mould layer on their undersides.

The source says: it is a common disease of lettuce, both under cover and outdoors.

How to protect

1. Prevention

   • Sow varieties resistant to downy mildew (e.g. 'Leny', 'Lettony'; resistance breaks down over time as new races appear).
   • Rotate lettuce around the bed; spores survive in the soil.
2. By hand as soon as it appearsRemove affected outer leaves straight away; you can often still harvest the hearts, then dispose of the rest of the plant.

Grey mould

What you will see

Soft, rotting parts covered in a fuzzy grey coating.

The source says: grey mould is common on this plant.

How to protect

1. Prevention

   • Keep things clean: remove dead and diseased parts.
   • Ventilate polytunnels and greenhouses.
2. By hand as soon as it appearsCarefully remove affected parts into a bag (spores spread easily) and dispose of them.

Aphids

What you will see

Colonies of tiny insects on young shoots and under leaves, stunted and distorted growth, sticky honeydew and black sooty mould on it.

How to protect

1. Prevention

   • Tolerate a small number: aphids are food for beneficial insects.
   • Check plants often so you can act in time.
   • Encourage ladybirds, hoverflies, lacewings and parasitic wasps.
2. By hand as soon as you spot themSquash colonies with your fingers or remove affected shoot tips.
3. Biological before a heavy infestationIn a greenhouse you can buy in hoverfly larvae, lacewings and parasitic wasps.
4. Chemical — only when nothing else helps according to the product labelLast resort only: a product authorised in your country against aphids. Try non-chemical methods first.

Root aphids

What you will see

Plants wilt and lag behind, leaves are pale; aphids sit on the roots, so they are hard to see.

How to protect

1. Prevention

   • Water and feed plants well; this reduces stress from the aphids.
   • Check the roots when planting.
2. By hand when foundDig up the affected plant, rinse the roots and replant in fresh soil; some aphids may remain, though.