Brown rot is a fungal disease of apples, pears, plums, cherries and other fruit and ornamental trees, causing a brown, spreading rot in fruit. It is caused by the same fungi that cause blossom wilt of the flowers and fruit spurs.
What is brown rot?
Brown rot is a fungal disease of top fruit, caused by the fungi Monilinia laxa and M. fructigena. The two fungi are very closely related and indistinguishable to the naked eye. M. laxa more commonly causes blossom wilt on pears and stone fruit, and a specific form, M. laxa f. sp. mali is restricted to apples. M. fructigena can cause brown rot in most fruit trees.
Many ornamental and fruit trees are affected, including apples, pears, plums, cherries, nectarines, peaches, apricots, including ornamental varieties.
Rotting fruit are found from mid-summer onwards.
You may see the following symptoms:
- Brown rot in the fruit, spreading out from wounds, especially those made by birds, codling moth and apple scab infection
- Affected fruit may remain hanging on the tree in a mummified state
- Buff-coloured pustules of the causal fungi on the fruit surface, often in concentric rings. Usually seen under wet conditions
- At flowering time the same fungi cause blossom wilt, where blossoms and leaves on fruiting spurs turn brown and shrivel
- Severity varies greatly from year to year, depending on weather conditions at flowering
Non chemical control
- Minimise carry-over of the pathogens by removing all brown rotted fruit promptly and composting. Do not allow rotted fruit to remain on the tree
- Brown rot infects through wounds, especially those caused by birds, so if possible, net to reduce bird damage
- Prune out and burn infected spurs and blossoms to reduce the amount of fungus available to infect fruit
- The plums ‘Czar’, ‘Jefferson’, ‘Ontario’ and ‘President’ have some resistance
The fungicide difenoconazole (Westland Plant Rescue Fungus Control) is labelled to control brown rot on cherries, plums, prunes, gages and damsons. Spraying susceptible trees at the beginning, peak and end of flowering may reduce the severity of the disease. Fungicides applied for other purposes, such as scab control, may give some incidental control though this is not claimed by the manufacturers.
Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)
Fruit becomes infected through wounds. Affected fruits mummify and may remain hanging on the tree and where they touch the bark they cause small infections (cankers). The fungus remains in the dead fruit and cankers over winter and releases spores in the spring to cause the blossom wilt phase of the disease. These infections in turn release spores to infect wounded fruit.
Common name Brown rot
Scientific name Monilinia laxa and M. fructigena
Plants affected Many ornamental and fruit trees, including apples, pears, plums and cherries
Main symptoms Brown, rotted fruit
Caused by Fungi