This year peach leaf curl has been devastating. Virtually affecting all of my peaches, nectarines, but not to any great extent on my almonds or apricots. Even the varieties that are supposedly resistant have been affected.
The fungus spores that produce the leaf curl, over winters in the bark and bud fissures. When the right spring conditions occur the fungus spores wash off the bark by rain and splash onto the buds, which it then penetrates the leaf tissue causing the characteristic leaf curl. Strangely it is supposed to be when cold and wet conditions occur in the spring.
In very worst cases all the leaves drop off, normally then followed by the tree producing new fresh shoots that are unaffected.
The most effective method is to prevent the spores washing into the buds by building a plastic shelter to keep the rain off. Keep this in place from January to April. Make sure the tree is ventilated by leaving the sides of the plastic open and allow the roots to receive water by leaving a gap near the ground.
Covering of open ground grown trees is not a reality. Therefore fungicides containing copper (Vitax Bordeaux Mixture, Fruit and Vegetable Disease Control) are said to give good protection. Spray in autumn just before leaf fall and twice, two weeks apart, in late January and early February.
To make a home made Bordeaux Mixture spray, measure out 6 ½ teaspoons of copper sulphate and 3 tablespoons of hydrated lime. The lime should be mixed with a pint of water to make a “milk of lime” suspension. The copper sulphate should also be dissolved in a pint of water. The latter process may take several minutes.
Before mixing the lime and copper components of the mixture, one additional step (but an important one) must be carried out. Each container of these materials should be strained through a cheesecloth filter. If cheesecloth isn’t available, use cloth of a similar loose weave. The filtering is necessary to remove small pieces of lime or copper sulphate that won’t dissolve; otherwise, you’ll find these tiny pieces in the end of your garden sprayer tip, clogging up the works!
To make the filter, simply place the cheesecloth loosely over the top of another container and fix securely in place with a string or rubber band.
The filtered copper sulphate solution is added to a one-gallon container, followed by addition of the filtered lime solution. Enough water is then added to the container to bring the total volume up to one-gallon.
You now have one gallon of Bordeaux Mixture ready for use.