I have a cotoneaster hegde that is very suseptible to a number of pests and diseases. The one problem that I have identified is the pear slug, but there are sections that appear fine and then the foilage shrinks and curls in on itself and then the disease spreads down the hedge until the foilage drops. There are spots in the hedge that don't come back after the winter--- these sections are enlarging. Help! I don't want to lose it all.