Tomato stunted growth
There are 9 common causes, and they need completely different responses — so working out which one you have matters more than treating quickly.
6 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 9 causes, and how to tell them apart
1.Bacterial Wilt
Act nowBacterial disease
Individual leaves wilt suddenly and dramatically while still fully green, then whole runners, then the plant. No yellowing, no spots — just collapse. Cut the stem, touch the two cut faces together and pull them slowly apart: sticky white threads stretch between them.
How to know it is this one
The string test: cut stem, press the faces together, pull apart. Sticky threads confirm it.
2.Fusarium Wilt
Act nowFungal 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.
3.Herbicide Damage
Act nowGrowing conditions
New growth twisted, cupped, fern-like or strap-shaped, with stems that may spiral. Leaves take on a leathery texture and abnormally prominent parallel veins. Older leaves below stay entirely normal.
How to know it is this one
Only new growth is affected; older leaves are untouched.
4.Mosaic Virus
Act nowVirus
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.
5.Root Rot
Act nowFungal disease
Above ground, yellowing and wilting that looks like drought but does not respond to water. Below ground, roots that are brown or black, soft, and smell sour — healthy roots are firm and pale, and the outer sheath of a rotted root slides off leaving a thread.
How to know it is this one
Wilting that does not improve after watering, and often gets worse.
6.Verticillium Wilt
Act nowFungal 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.
7.Aphids
TreatablePest
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.
8.Flea Beetles
TreatablePest
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.
9.Nitrogen Deficiency
TreatableNutrient 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.
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