Is this what the caterpillars and leaves look like? If so then a boilogical agent like Spinosad or Dipel could do the trick. These are relatively safe products to use as they are completely biodegradable, but the disadvantage is you may need to re-apply on a daily basis. Don't apply before rain, or if it's going to rain in 24hrs. I control these little monsters with my fingers, and they usually infest my quince and plums in spring.
