Why is my fruit rotting on the plant?
Fruit rots split cleanly into three groups: a fungus that entered through the skin, an insect that bored in and left a fungus behind, and a disorder where nothing infected the fruit at all. The position of the damage on the fruit tells you which group you are in.
The one observation that decides it
Find where it started. A sunken dark leathery patch at the BLOSSOM end — the bottom, opposite the stalk — is blossom-end rot, a calcium and watering problem with no pathogen involved, and no spray will touch it. A small hole near the STALK with brown crumbly frass is a boring caterpillar. An expanding firm brown rot with tan spore tufts, on a fruit still hanging, is brown rot. Soft watery collapse with grey fuzz is botrytis, and a split that rotted afterwards started as fruit cracking after rain.
Start from the plant in front of you
13 things it could be
Ordered by how much they can cost you — if the first entry fits what you can see, rule it out before considering the milder ones.
Dark, water-soaked greasy patches on leaves that rapidly turn brown; white fuzzy sporulation on leaf undersides in humid mornings; firm brown lesions on stems and fruit. Whole plants can collapse within days.
Conditions: 10–25°C · humidity ≥90% · wet leaves / rainFirst move: Remove affected material nowDark, sunken circular lesions on fruit often oozing pink spore masses when wet; irregular dead blotches on leaves along veins; cankers on stems and twigs.
Conditions: 20–30°C · humidity ≥85% · wet leaves / rainFirst move: Treat, then re-check in 5–7 daysSeen on: Cucumbers, Beans, Raspberries, Blackberries, Walnut trees
A small water-soaked spot spreads into a soft, wet, cream-to-brown mush with a distinctive foul smell. In stored bulbs and tubers the inside collapses while the skin still looks intact. Standing plants wilt and topple at the rotted point.
Conditions: 20–32°C · humidity ≥90% · wet leaves / rainFirst move: Treat, then re-check in 5–7 daysBlossoms wilt and turn brown (blossom blight); fruit develops expanding brown firm rot covered with tan spore tufts; mummified fruit clings to the tree over winter.
Conditions: 18–28°C · humidity ≥85% · wet leaves / rainFirst move: Treat, then re-check in 5–7 daysSmall entry holes plugged with brown crumbly frass on fruit, tunnels bored to the core, premature fruit drop, and pinkish-white caterpillars inside.
Conditions: 15–32°CFirst move: Treat, then re-check in 5–7 daysSeen on: Apple trees, Pear trees
Tan circular leaf spots with dark borders dotted with black specks; berries turn brown then shrivel into hard black mummies that stay on the cluster.
Conditions: 15–27°C · humidity ≥85% · wet leaves / rainFirst move: Treat, then re-check in 5–7 daysSeen on: Grapes
Fuzzy grey-brown mould on flowers, fruit and stems; soft watery rot; tan spots with concentric zoning on leaves. Spores puff out in clouds when disturbed.
Conditions: 5–22°C · humidity ≥90% · wet leaves / rainFirst move: Treat, then re-check in 5–7 daysSeen on: Grapes, Strawberries, Raspberries, Blackberries, Redcurrants, Gooseberries and 10 more
Fruit softens and collapses within a day or two of looking perfect, with a tiny puncture scar on the skin. Cut it open and there are small white maggots inside. Whole pickings of raspberries turn to mush overnight.
Conditions: 15–30°C · humidity ≥70%First move: Treat, then re-check in 5–7 daysSeen on: Cherries, Grapes, Raspberries, Blackberries, Blueberries
A sunken, leathery, dark brown-black patch at the blossom (bottom) end of the fruit, often on the first fruit of the season or during dry spells; the rest of the fruit may ripen normally.
Conditions: Spread by handling, insects or soil — not weather-triggeredFirst move: Fix the cause, not the leafSeen on: Tomatoes, Peppers, Aubergines
Premature ripening and fruit drop from July. A small hole near the stalk with brown crumbly frass around it, and a pinkish-white caterpillar in a tunnel beside the stone when the fruit is cut.
Conditions: 15–30°CFirst move: Treat, then re-check in 5–7 daysSeen on: Plums
Dried, browned patches at the stalk end of the fruit, and a small cream-coloured grub in the core when the fruit is picked or eaten. Flowers may show feeding damage earlier in the season.
Conditions: 15–28°CFirst move: Treat, then re-check in 5–7 daysSeen on: Raspberries
Concentric or radial splits in the skin around the stem or across the fruit, which then invite rot and insects; most common after rain on ripening fruit.
Conditions: wet leaves / rainFirst move: Fix the cause, not the leafPale, papery, blistered or sunken bleached patches on the sun-exposed side of fruit that may later rot; on tree trunks, cracked, sunken dead bark on the south-west side.
Conditions: 32–45°C · dry air ≤50%First move: Fix the cause, not the leaf