Shortly before harvest a fine fruit starts to turn brown, covers itself with pale cushions and rots on the branch. Brown rot is a common and annoying problem on apple, pear, cherry and plum. But it has a clear weak point you can target.
This article is the detail edition to the overview in Recognising fruit tree diseases. Understand how the fungus overwinters and gets into the fruit and you can curb it effectively with simple tree hygiene.
How to recognise brown rot
The damage picture is clear. On the fruit a brown, soft rotten patch forms and spreads quickly. On it grow pale, yellowish-grey spore cushions, and indeed in conspicuous concentric rings, like the annual rings of a tree. The fruit finally dries into a hard, dark mummy.
Affected are both pome fruit like apple and pear and stone fruit like cherry, plum and apricot. The fungus almost always needs an entry point: a wound from wasps, birds, hail, the codling moth or a scab crack. Through this injury it enters, and from fruit to fruit it jumps on contact.
The key: the mummified fruit
Here lies the most important point of attack. The dried, affected fruit, the mummies, do not simply drop but often hang on the tree all winter. In them the fungus survives and, in spring, hurls its spores onto the new blossoms and fruit.
Remove these mummies consistently and you break the cycle at its most sensitive point. In winter, gather all dried fruit from the tree and the ground and dispose of it in the residual waste, not on the compost. This one measure works more than any spray.
How to prevent it
Remove the mummified fruit
In autumn and winter, gather every dried fruit from the tree and the ground. That is the most effective single measure, because it takes the fungus's winter quarters.
Avoid fruit wounds
Because the fungus enters through injuries, everything that keeps the fruit intact helps: fend off wasps and birds, keep an eye on the codling moth and keep scab small through resistant varieties.
Keep the crown airy
In an airy crown the fruit dries faster and the fungus spreads more slowly. How to prune correctly is in Summer pruning of fruit trees.
Harvest and store carefully
Harvest gently so the fruit gets no bruises, and store only flawless fruit. A single rotting fruit quickly infects its neighbours in store.
No mummy on the tree, no infection next year. The fight against the rot is won in winter by hand, not with the spray.
The core rule against brown rot
Frequently asked questions
How do I reliably recognise brown rot?
By brown, soft rotten spots with pale spore cushions arranged in concentric rings. Later the fruit dries into a hard mummy. This ring structure is typical and hardly to be confused.
Why are the mummified fruit so important?
Because the fungus overwinters in them. If they stay on the tree, they scatter the spores for the next attack in spring. Consistently removing all mummies from tree and ground is therefore the most important measure.
Can I still use affected fruit?
Rotten fruit affected by Monilia belongs in the bin, not on the compost and not in the kitchen. Still healthy fruit from the same tree you can harvest and use normally, best promptly.
Does a spray help against the rot?
In the home garden there are hardly effective products, and they are not needed either. The combination of removing mummies, avoiding wounds and an airy crown keeps the rot small more reliably than any spray.
Why do my pecked fruit rot in particular?
Because the fungus needs a wound as an entry point. Where wasps, birds or the codling moth have injured the skin, Monilia settles especially easily. Intact, uninjured fruit, by contrast, usually stays healthy.
