Pepper stunted growth

There are 6 common causes, and they need completely different responses — so working out which one you have matters more than treating quickly.

3 of them can kill the plant. Rule those out first.

Check these two things first

  • Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
  • Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.

Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.

The 6 causes, and how to tell them apart

1.Fusarium Wilt

Act now

Fungal disease

Yellowing and wilting that often affects one side of the plant, or one branch, while the rest looks fine. Slice the main stem lengthwise near the base and the tissue just under the skin is stained chocolate brown instead of pale green.

How to know it is this one

Cut the stem lengthwise: brown staining in the ring just under the skin confirms it.

Full treatment for fusarium wilt

2.Mosaic Virus

Act now

Virus

A patchwork of light and dark green across the leaf, giving a mottled or marbled look with no clear spot edges. New leaves come out narrow, puckered, strap-like or fern-like. Fruit is small, mottled and often fails to set.

How to know it is this one

Light and dark green mottling with soft, blurred boundaries.

Full treatment for mosaic virus

Fungal disease

Yellow wedges spreading inward from the leaf edges, often forming a V shape pointing at the midrib. Lower leaves go first. Cutting the stem shows brown discolouration in the vascular ring, usually lighter than fusarium's.

How to know it is this one

V-shaped yellow wedges at the leaf margins.

Full treatment for verticillium wilt

4.Aphids

Treatable

Pest

Clusters of small soft-bodied insects, usually green but also black, grey, pink or white, packed along new shoots and the undersides of young leaves. Leaves curl and pucker, and everything below becomes sticky with honeydew.

How to know it is this one

Dense clusters on new shoots and flower buds rather than scattered individuals.

Full treatment for aphids

5.Flea Beetles

Treatable

Pest

Dozens of tiny round holes through the leaf, as though it had been hit with birdshot. The beetles are minute, dark and shiny, and jump like fleas when disturbed — which is usually all you see of them.

How to know it is this one

Many small round shot-holes rather than a few large ones.

Full treatment for flea beetles

Nutrient problem

Uniform pale yellowing of the whole leaf, including the veins, starting with the oldest lowest leaves and working upward. Growth is slow and the plant looks generally thin and pale.

How to know it is this one

Whole leaf yellows evenly, veins included.

Full treatment for nitrogen deficiency

Still not sure?

The diagnostic key adds two more questions — which part is affected and where the trouble started — and those usually settle it.

Run the diagnostic key