Leaf Curl on Peach Trees and other fungus:
Peach leaf curl causes leaves of peaches and nectarines to discolor, thicken, pucker, curl, distort and eventually fall off. The fungus overwinters in these trees as spores, usually in the new buds. The rains splash these spores onto the emerging leaves, causing more problems.
Onion spray is very effective against disease organisms such as molds and fungus. California fruit grower Roger Dondero mixed up his own spray to see if it would help the leaf curl on his peach trees. Within a few weeks, the fungus on the leaves turned black and fell off after just spraying the trees heavily for three evenings in a row. Within a few weeks, all the fungus turned black and fell off. This spray can also be used on vegetables being destroyed by cutworms or aphids. One gardener states that he just ties the stems of wild onions to his plants to get rid of cutworms.
Put a few onions in a blender with water. Let this puree sit overnight and then strain the onions out so it will go through a spray bottle. Keep refrigerated so it doesn’t spoil. This will have to be re-applied each time it rains. You can add a few drops of dish soap or vegetable oil to the spray to get it to stick to the leaves better. Shake well before each application.