Tomato rotting fruit
There are 5 common causes, and they need completely different responses — so working out which one you have matters more than treating quickly.
1 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 5 causes, and how to tell them apart
1.Late Blight
Act nowFungal disease
Large irregular blotches that look greasy or water-soaked, grey-green at first and turning brown-black. In humid weather a fine white fuzz appears on the underside at the edge of each lesion. Fruit develops firm, greasy brown patches.
How to know it is this one
Lesions look wet or greasy rather than dry and crisp, even in dry weather.
2.Anthracnose
TreatableFungal disease
On fruit, circular sunken spots that darken and develop concentric rings of tiny black dots, often with a pinkish spore ooze in wet weather. On leaves, irregular brown blotches that frequently follow the veins.
How to know it is this one
Sunken circular lesions on ripe fruit that deepen over days.
3.Blossom End Rot
TreatableNutrient problem
A flat, sunken, leathery brown-black patch on the bottom of the fruit — the end opposite the stem, where the flower was. It starts as a small water-soaked spot and enlarges. The rest of the fruit looks perfectly healthy.
How to know it is this one
Always at the blossom end, never the stem end, and never on the side.
4.Grey Mould (Botrytis)
TreatableFungal disease
A soft, dusty grey-brown fuzz that puffs into a cloud of spores when disturbed. It colonises dead or damaged tissue first — spent flowers, pruning wounds, bruised fruit — then moves into healthy tissue beside it.
How to know it is this one
Grey fuzzy growth that releases a visible puff of spores when touched.
5.Sunscald
Mostly cosmeticGrowing conditions
On fruit, a pale whitish or yellow patch on the shoulder facing the sun, which becomes papery, sunken and sometimes greyish as it dries. On leaves, bleached or brown patches on the most exposed surfaces rather than at the edges.
How to know it is this one
Damage on the side facing the sun, not the blossom end or stem end.
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