Tomato problems
Tomatoes get more diseases than anything else in a vegetable garden, and most of them start on the lowest leaves and work upward. Where the trouble starts is usually more informative than what the spots look like.
Start from what you can see
Each of these has more than one possible cause, and each page separates them.
Everything that commonly affects tomato plants
Most serious first. Most of the list is treatable or can be ignored.
Bacterial disease
The string test: cut stem, press the faces together, pull apart. Sticky threads confirm it.
Fungal disease
Cut the stem lengthwise: brown staining in the ring just under the skin confirms it.
Growing conditions
Only new growth is affected; older leaves are untouched.
Fungal disease
Lesions look wet or greasy rather than dry and crisp, even in dry weather.
Virus
Light and dark green mottling with soft, blurred boundaries.
Fungal disease
Wilting that does not improve after watering, and often gets worse.
Pest
Fine even stippling rather than discrete spots or holes.
Fungal disease
V-shaped yellow wedges at the leaf margins.
Fungal disease
Sunken circular lesions on ripe fruit that deepen over days.
Pest
Dense clusters on new shoots and flower buds rather than scattered individuals.
Bacterial disease
Greasy, water-soaked appearance, especially in the morning.
Nutrient problem
Always at the blossom end, never the stem end, and never on the side.
Fungal disease
Concentric rings inside each brown spot — the bullseye is the giveaway.
Pest
Many small round shot-holes rather than a few large ones.
Fungal disease
Grey fuzzy growth that releases a visible puff of spores when touched.
Nutrient problem
Whole leaf yellows evenly, veins included.
Fungal disease
Very many small spots rather than a few large ones.
Pest
Whole stems stripped to bare stalks, not scattered holes.
Growing conditions
Leaves dry and crisp rather than soft and limp.
Pest
A cloud of tiny white insects that flies up when you shake the plant.
Growing conditions
Damage on the side facing the sun, not the blossom end or stem end.
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.
Diagnose your tomato
Already filtered to tomato plants. Add the symptoms and where the trouble started.
1.What plant is it?
Many problems are specific to one family, so this removes a large share of the list straight away.
2.What does it look like?
optionalPick everything you can see. Any one match keeps a cause on the list, because you rarely see the whole picture at once.
3.Which part is affected?
optionalIf the roots are involved you will have to unpot or dig to find out — and with a declining plant that is usually the most informative thing you can do.
4.Where did it start?
optionalThe most underused question in plant diagnosis. Trouble that begins at the bottom means something very different from trouble that begins at the top.
- Bacterial WiltAct nowBacterial disease
- Fusarium WiltAct nowFungal disease
- Herbicide DamageAct nowGrowing conditions
- Late BlightAct nowFungal disease
- Mosaic VirusAct nowVirus
- Root RotAct nowFungal disease
- Spider MitesAct nowPest
- Verticillium WiltAct nowFungal disease
- AnthracnoseTreatableFungal disease
- AphidsTreatablePest
- Bacterial Leaf SpotTreatableBacterial disease
- Blossom End RotTreatableNutrient problem
- Early BlightTreatableFungal disease
- Flea BeetlesTreatablePest
- Grey Mould (Botrytis)TreatableFungal disease
- Nitrogen DeficiencyTreatableNutrient problem
- Septoria Leaf SpotTreatableFungal disease
- Tomato HornwormTreatablePest
- UnderwateringTreatableGrowing conditions
- WhitefliesTreatablePest
- SunscaldMostly cosmeticGrowing conditions