Cherry Shot Hole: how to tackle it

I had a question from Marta, one of my regulars, a few days ago (*waves to Marta*): one of her Cherry trees is suffering from a fungal attack, and she wasn't quite sure what to do about it.

Here is a leaf, showing the damage - lots of small holes, puncturing the leaf.

It looks as though someone has been shooting the leaves, and - amusingly - the name for this problem is Cherry Shot Hole Disease.

Because it looks as though someone has fired a shotgun through it.

So, what's Shot Hole Disease, then?

Firstly, it's a catch-all term for a number of fungus and bacterial attacks: I won't give you the scientific names because - well, it doesn't really matter exactly which one you have, the treatment is going to be the same.

The pathogen (which can be fungus or bacteria) is spread by spores, which land on the leaves, and form tiny lesions, or spots. Usually reddish-brown, sometimes quite black.

As these spots grow, the fabric of the leaf dies, and the dead material falls out, leaving a small hole right the way through the leaf.

Later in the summer, the affected leaves turn yellow, and then drop off.

Obviously, this looks dreadful, and is not good for the tree! If left untreated, the tree will eventually die. Well, ok, all trees will die "eventually", but an infected tree will die in a couple of years, far sooner than it ought to.

So what can we do about it?

First things first, we need to break the cycle of spore infection. There's no point spraying anything onto the tree once the infection is present: but in autumn, every single leaf must be raked up and burnt, or put into your green waste bin (the council green waste is processed at high temperatures, which should kill all spores) (and if you are interested, read all about it here!).

This means that you have to keep looking out for falling leaves, and clear up every single one. They don't all fall neatly on one day, so start in late summer, and be vigilant. The spores are formed on the dead leaves over the winter, and released the following spring, so it's important to clear them all away.

This doesn't mean that you have to pick all the leaves off the tree - you can wait for them to fall naturally, but if some of the leaves are mostly yellow, and are clearly really badly damaged, then yes, you can go up a ladder and carefully pick off the damaged leaves. They should be easy to remove, because they are already dying - but make sure you don't damage the branches by ripping the leaves off when they are not ready to be removed.

Right, so now we've removed the main source of spores: but there will still be some spores around, not least because they float through the air, and if anyone else nearby has a Cherry (or any other Prunus such as Plum, Cherry Laurel, etc) which is infected, then their spores might drift over onto your trees.

So, as soon as the leaves start to appear, treat the whole tree with a systemic fungicide, which you will need to apply fortnightly (or as per the instructions on the pack) from the first signs of leaves appearing, which will be Feb and March. 

This might sound like an impossible task - how do you spray an entire tree? - but most Cherry trees are comparatively small, and there won't be a canopy of leaves, so at least you can see what you are doing.  Use a good quality spray bottle: wear a mask, gloves, long sleeves, and goggles: and spray from the bottom up, otherwise you find that you get dripped on when you try to spray the lower branches.

If this sounds too daunting, get someone with a spray licence to do it for you: contact your local arborist firms, they should either be able to do it, or will know someone who can.

Hopefully, by clearing up all the debris in autumn, and spraying early the following spring, your Cherry trees will be able to produce undamaged leaves, and will regain their full vigour.

As always with fungal problems, good airflow is helpful, so if your tree is very congested, it might be worth thinning out some of the canopy, to allow light and air to pass freely through the tree. Cherry trees should be pruned every 3-5 years anyway, to keep the canopy open, and to remove dead or damaged branches, and this can really help to keep the tree healthy.

And as a general point, I would suggest ensuring that the base of the tree is clear of weeds and grass, so that it's not having to deal with too much competition: if it's a dry spring, then water it well, once a week for a few weeks: and you could give it some balanced feed such as Growmore, scattered around the base of the tree, or a liquid feed such as liquid Seaweed, watered in well.

As the year progresses, keep an eye on the tree, and if necessary, repeat the whole process again in autumn, followed by spraying again the following spring.

Hopefully, this will allow your Cherry to recover. If, however, you can't seem to beat the infection, then it might be better to replace the tree with a Cherry which is resistant to disease: but it's always worth trying to save your existing trees, if you possibly can.

Did you enjoy this article? Did you find it useful? Would you like me to answer your own, personal, gardening question? Become a Patron - just click here - and support me! Or use the Donate button for a one-off donation. If just 10% of my visitors gave me a pound a month, I'd be able to spend a lot more time answering all the questions!!