Advice
RHS Help & Advice
Blossom wilt
Hosts
Apple,
pear, plum, cherry, peach, apricot and ornamental Prunus.
Some related ornamental trees such as Amelanchier
may also be affected.
Prunus ‘Spire’ and ‘Kiku-Shidare’
and apple ‘Lord Derby’ are particularly susceptible.
Symptoms
Symptoms appear after flowering, as browning and wilting of the flowers and surrounding leaves. These remain hanging on the spurs. In serious attacks the spurs and small branches may also be killed.
Biology
The fungus Monilinia laxa is responsible for this disease. It also causes the fruit disease brown rot in stone fruit; in apples and pears brown rot is usually caused by the closely related Monilinia fructigena.
Buff coloured spores develop on dead tissues in damp conditions. These spread to opening flowers on air currents, especially in damp conditions.
Control
No fungicides are specifically labelled for the control of this disease. However, several fungicides are labelled for control of other diseases on certain fruit and ornamental trees, and could be used at the owner’s risk. These are copper-containing fungicides (Bordeaux Mixture and Murphy Traditional Copper Fungicide) and myclobutanil (Systhane Fungus Fighter). Check the label to see on which trees the products can be used. These products have been approved for use on these plants and are therefore safe to the operator when used as directed. However, they carry no specific recommendations for application rates or frequencies against blossom wilt and there is no guarantee of efficacy. Applications at the rates recommended for other diseases could be made just before bud burst (not during flowering to avoid damage to bees) and may give some control.
Prune out infections in summer and do not allow brown rotted fruit to remain on the tree as these can infect bark and allow the fungus to overwinter.
Resistant cultivars
Apricot: ‘Monique’ and ‘Moorpark’
Plum: ‘Jefferson’, ‘Marjorie’s Seedling’,
‘President’, ‘Reine Claude Violette’