I'm located in California's Central Valley. I have several apricot trees which have been afflicted with an unidentified disease in most years. Many of the leaves curl up and die during the summer, and the fruit withers and falls off before it ripens.

I haven't identified the disease, but all of the possibilities appear to be fungal, and I know that one basic preventive measure is to clear the fallen leaves away from the tree. I want more clear advice on what that means: how thoroughly must the leaves be cleared, and how far from the trunk?

The trees grow next to the base of a retaining wall about a foot high. In two cases there's a chain link fence along the top of the wall with a hedge behind it. In one case there's a storage shed flush with the wall, and on another side is a chain link fence that separates my property from a neighbor's.

I've raked up most of the leaves in the accessible areas for three or four feet from the base of each tree, except in the last case, where the property line is only a couple of feet from the base. Cleaning under the hedge would be very difficult. Going into the neighbor's yard is out of the question.

How good a job have I done? If I need to do more, any suggestions on the measures that would be most effective?