Hawthorn lace bug causes a gray, lacy spotting of the upper leaf surfaces. Brown specks on the lower leaf surfaces are insect excrement. Use Sevin dust or sprays of acephate.
Several scale insects attack cotoneaster, including oystershell and San Jose scale. The insects can build up to large numbers without being seen. Sprays of dormant oils applied in the spring kill overwintering scales. Crawlers can be controlled with sprays of Sevin or acephate. Oystershell scale crawlers may be controlled with malathion. A combination of regular inspection for early detection then a dormant oil spray is the preferred method of control.