For those with peach, nectarine, apricot, plum or almond trees in particular, it's almost time to treat your trees before bud burst in order to prevent any hibernating fungal growths from infecting the new growth.
As soon as you see the pink starting to show on the buds, spray your tree - it is not possible to control the fungus once it's entered the leaf, so don't leave it for the buds to open.
For those in the Dandenongs foothills, it may well be time to spray very soon as I've noticed one bud on a new peach tree starting to open. Then of course the temp dropped several degrees and we had rain and hail for a couple of days, so maybe over the next week...
The solutions below all work by temporarily altering the pH of the bark where the fungus overwinters and killing it off, without harming the tree itself.
Try alternately spraying with bicarb soda and then, a few days later, with vinegar solution. Some say apple cider vinegar works best, but I've never tried this.
You can also try spraying with milk, which is commonly used to spray plants such as roses :)
For the more adventurous, try making your own lime-sulphur mix by simply adding sulphur and hydrated (builders lime) with boiling water. For every 5l of boiling water, you need 1kg of sulphur and 500g of lime.
**WARNING - Don't get it on your skin or in your eyes! Wear gloves, eye protection and use a metal implement. The builders lime is very caustic and getting it in your eyes could damage your sight permanently**
PS - do not your DH's BBQ mate or missus favourite spatula as you will not be popular!
You'll need to boil the water in a stainless steel pot. Whilst the water is boiling, simply mix up the sulphur and lime, whilst trying to break up any lumps. Add the mixture to the boiling water and stir frequently for around 35 - 45 minutes. You will see the mixture change to a red colour (this may take longer depending on the quality of the lime).
Once the liquid has changed colour, you need to use a metal sieve and a funnel that will take hot water, to pour this into a container for cooling. Once cooled, store in an airtight container in a dark place for up to 6 months.
For goodness sake, don't forget to label it and put it out of reach of the kids!
There will be some particulates in the liquid which will settle over time. Simply give the bottle a shake before using.
The liquid should be diluted to about 50mls per litre of water. I find that a few drops of biodegradable phosphate free detergent helps in getting it to stick to your tree.
Spray immediately before budswell and then one week later, at budswell. You may also wish to spray again after leaf fall in autumn and this might be required if you leave the spray at budswell too late and notice symptoms through the growing season.
Spray on a dry day, when there's no breeze and preferably when there's no rain expected for at least 24 hours. Hard in this area at this time of year, but give it a go :)
Please do not spray this on any green vegetation, flowers or fruit as peaches and apricots are sulphur sensitive. Also should not be sprayed on Delicious or Cox's Orange Pippin apples or members of the cucumber family AT ANY TIME.
You may also wish to consider taking precautions (i.e. wearing a mask) when spraying as it's not great on the lungs if you breathe it in.
For the yeuchy green stuff at the bottom of your pot and in your sieve, this can be kept in a glass jar and used to paint over wounds and cuts when pruning or removing damaged branches.
Now, I've heard other formulas for lime-sulphur that include Diatomaceous Earth or ash (replaces half the lime), but I've not personally tried these. I would be interested in hearing how you guys have gone with these variations and of course what other organic methods you might use :)
And don't forget - the healthier your soil and plants are, the less chance they have of succumbing to disease or pests. Apply Dynamic Lifter at a rate of 500g for each year of the trees age, to around 5kg max, and water this in well. I would of course water it in with a seasol, molasses and compost tea mix myself :)
UPDATE: We only managed to spray once because when the peach was purchased this year it was already at bud swell. Consequently, in November there were lots of affected leaves which I picked off by hand and binned. The tree was given lots of dynamic lifter, Seasol, magic potion and compost to get it through and now it's January 2013 and there's very little signs of peach leaf curl on the leaves and the tree is very healthy.
The key points that worked in our treatment plan seem to have been picking off affected leaves by hand in the early part of the growing season and ensuring the tree was well watered and fed to promote healthy growth. Therefore we will likely see how the tree fares next year before we apply any more lime sulphur.