What is it.
Known as Taphrina deformans leaf curl is a fungus that loves cold and wet conditions. It also loves peach, almond and nectarine trees, where it likes to live during the winter months. As the tree buds swell the fungus gets to work infecting the leaf cells. This stimulates the leaves to grow larger than normal and often with a reddish tinge. To be honest leaf curl affected leaves look pretty hideous, and anyone unfortunate enough to have seen or read ‘The Day of the Triffids’ will no doubt think they’re experiencing just that.
What you can do about it.
There are a number of sprays available – most of them being copper based. Now this started out with some French peasants in the late 19th century who were getting very grumpy as passers by kept stealing their grapes. Noting the vivid colour left on the vine leaves when sprayed with blue stone (copper sulphate) the peasants discovered no-one stole their prized fruit for fear of the blue poison! Don’t you love it when two wrongs make a right. An unexpected outcome of the new deterrent was a big reduction in fungal diseases and therefore an increase in yield. Voila! Bordeaux mixture was born and aptly named named after the city that now produces 700 million bottles of wine annually.
Making your own Bordeaux mixture
(Ingredients available at most hardware stores and nurseries)
Dissolve 100 gram of builders’ (hydrated) lime in half a standard (plastic) bucket of water. (About 5 litres).
Dissolve 100 grams copper sulphate (aka blue stone) in a separate half bucket of water.
Keep stirring the lime mixture to prevent it settling and pour it steadily into the half bucket of dissolved copper sulphate.
Add enough extra water to make up a total of 10 litres of the finished Bordeaux mixture.
It is at its most effective strength when freshly mixed so used immediately or within a couple of days. Using it straight away also means it’s less likely to clog spray nozzles etc.
If you’re not up for the above alchemy go for the following off-the-shelf least toxic ways to deal with leaf curl:
Lime Sulphur has been around for a long time hence is still favoured by organic operators. As with the copper based sprays it will damage foliage so ensure the tree is dormant.
Cupric Hydroxide has the advantage of being able to be sprayed after leaves are visible. You’ll see this marketed as a next generation copper spray that needs less copper to do the job.
They had me at “plasma technology”
Safety first for you, your trees and your soil
Only spray while the trees are dormant i.e. the buds haven’t burst and no leaves are visible. Copper based sprays will burn leaves which really stresses out a tree that may already be fighting leaf curl so if it’s too late and spring has sprung just make a note to do earlier next year.
Spray to cover all the bare branches of peach, nectarine and almond trees. You need to spray enough so it’s dripping (see pic below). Wear old clothes and safety glasses plus gloves. I did this once in black sneakers and they now have a blue speckled look… If you choose one of the copper based spray options, be mindful that this is a heavy metal and will accumulate in the soil below your trees. Over years this can add up so it pays to lay out some builders plastic/old curtains under the drip line to protect the ‘good’ fungi we want to encourage in your soil.
Don’t leave it for another week! Get out there this weekend and make sure this you tube clip is the only curling going on at your place.