Blossom wilt is a fungal disease of apples, pears, plums, cherries and related ornamental trees. It kills blossoms, spurs and small branches. The problem is caused by the same fungi responsible for brown rot of the fruit.
Scientific name Monilinia laxa and M. fructigena
Plants affected Many trees, including apples, pears, plums and cherries
Main symptoms Brown and shrivelled blossom and leaves
Caused by Fungi
What is blossom wilt?
Blossom wilt is a fungal disease of trees, especially fruit trees, caused by the fungi Monilinia laxa and M. fructigena. The two fungi are very closely related and indistinguishable to the naked eye. M. laxa is the most common cause of blossom wilt on pears and stone fruit, whilst a specific form, M. laxa f. sp. mali is restricted to apples. Whilst occasionally causing blossom wilt, M. fructigena more commonly causes the disease known as brown rot in the fruit.
Many tree fruit are affected, including apples, pears, plums, cherries, nectarines, peaches, apricots, and ornamental varieties.
The damage begins at flowering time in mid-spring, but becomes more obvious as shoots die back in late spring and early summer.
You may see the following symptoms:
- Brown and shrivelled blossoms and leaves on the fruiting spurs at flowering time
- Small, buff-coloured pustules of the causal fungi on dead tissues. Usually seen under wet conditions
- Severity varies greatly from year to year, depending on weather conditions at the time of flowering
Non chemical control
- Minimise carry-over of the pathogens by removing all brown, rotted fruit promptly. To dispose of fruit, you can bury them at least 30cm (1ft) below the soil surface, or put them in the local council green waste (although check first as some councils will not accept large volumes of rotting fruit). 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
- If practical, prune out and burn infected spurs and blossoms to reduce the amount of fungus available to infect fruit
- Choose resistant cultivars: apricots ‘Monique’ and ‘Moorpark’; plums 'Jefferson', ‘Marjorie’s Seedling’, ‘President’ and ‘Reine Claude Violette’ are resistant. The apple cultivars 'James Grieve' and ‘Lord Derby’ are very susceptible
There are no fungicides labelled specifically to control blossom wilt. On ornamental trees only, fungicides applied for other purposes, such as powdery mildew or rust 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, particularly bird damage. Affected fruits exhibit brown rot, mummify and remain hanging on the tree and, where they touch the bark, 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.
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