Join the RHS today and support our charitable work
Free personalised gardening advice
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Free entry to RHS members at selected times »
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Join the RHS today and support our charity
I have forgotten my password
Register for free to receive our newsletters, add comments to blogs/articles and to save content.
See what events are on near you and browse your bookmarked pages.
Tar spot is a very conspicuous fungal leaf spot disease of sycamore and some other maples. Whilst the large leaf spots sometimes cause gardeners concern, they actually do very little damage to the tree.
Tar spot of maple
Tar spot is a leaf spot disease caused by the fungus Rhytisma acerinum. It is seen most commonly on sycamore, but can also affect a number of other acer species. The spots are unsightly, and the disease can cause slightly premature leaf fall. It has no long-term effect on the vigour of affected trees, however.
You may see the following symptoms:
If the disease is considered unsightly on ornamental maples, some reduction in infection levels for the following year may be obtained by sweeping up and burning the fallen leaves.
There are no fungicides available to home gardeners for the control of tar spot.
Tiny fruiting bodies develop during winter on disease-affected fallen leaves at the base of the tree. The fruiting bodies produce microscopic spores that are released in April and May. The spores are carried upwards by air currents to infect the newly-emerging leaves.
No long-term damage is done to affected trees. Even if the leaves are shed slightly prematurely, by the time that they fall they have already made the bulk of their contribution to the growth of the tree for that year.
There are a number of genetically-distinct ‘races’ of the fungus, which vary in the species of acer that they affect.
Acer: leaf scorchDisposing of diseased materialJapanese mapleVerticillium wilt
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.