Every September we get customers bringing in thickened bubbly curled and distorted leaves from their peaches and nectarines, by then it is too late to treat and all we can do is offer a rueful smile and tell people what to do for next year. This is Peach Leaf Curl, a very unsightly and damaging problem caused by the fungus Taphrina deformans. If left untreated, it can cause dieback of new shoots, early fruit drop, reduction of vigour, and eventually death of the tree. The cool wet spring conditions in Victoria are ideal for this particular fungus, so you need to be proactive in controlling this disease.
If you have a bad infestation then apply three sprays in the first year to get it under control. Initially spray in autumn at leaf fall, then a week or so before bud swell in winter, and finally at bud swell (about a week later). Timing is critical, if you leave it too late, you have wasted your time. If there is significant improvement the following spring then you can move to a single spray at bud swell.
Which fungicide do you use? There are several options available to you. You can use one of the commercially available copper or lime based fungicide sprays, or you can make up a Bordeaux or Burgundy spray (these make the trees look slightly blue and are used when trees are completely dormant – never ever when they are in leaf).