Sweet corn

European corn borer

What you will see

Broken or snapped tassels (male flowers), holes at the break with frass and droppings in the leaf axils; larvae bore into the stalk.

The source says: it is the most important pest of maize.

How to protect

1. Prevention

   • Plough in deeply or bury sweetcorn debris after harvest (most effective, about 25 cm in the field); shredding alone is not enough.
   • Larvae overwinter in stubble, so do not leave debris on the bed.
2. Biological at the start of moth flight and again after 12–14 daysUse Trichogramma parasitic wasps against the pest's eggs; the average reduction is about 55%. Heavy rain right after release reduces the effect.
3. Gentle spray when larvae hatch, before they bore inBacillus thuringiensis has a weak effect (below 30%), as it breaks down quickly in sunlight.

Smut (sweetcorn)

What you will see

Spots, blisters, distortions and dark spores; symptoms vary with the type of smut.

How to protect

1. Prevention

   • Grow resistant sweetcorn varieties (they exist).
   • Destroy affected plants and rest the soil.
2. By hand when foundDestroy affected plants; rest the soil from that crop for several years.

Mice and voles

What you will see

Freshly sown sweetcorn seeds eaten, seedlings gnawed; in cold weather they enter polytunnels.

How to protect

1. Prevention

   • Protect freshly sown seeds and seedlings with a cover or netting.
   • In cold weather, check the greenhouse and cold frame.
2. By hand after sowingCover sown rows with netting or a cover and check for damage.

Badgers

What you will see

Churned-up lawns and beds, damaged vegetables and fruit, tunnels dug under fences.

How to protect

1. Prevention

   • Protect sweetcorn with fencing: metal mesh buried at least 50 cm deep; first check that there is no sett in the garden and that it is not an important badger route.
2. By hand before the cobs ripenMetal mesh buried at least 50 cm deep around the bed. If a badger digs underneath, a two-way gate is an option. Do not feed badgers. Electric fencing is not recommended.

Slugs and snails

What you will see

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

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.