Clicker train "Leave it" to your dog from the comfort of your own home! Follow the steps in this PDF file to learn how to train your dog how to leave things like food untouched when cued to do so. 
 
Disclamer: Please be aware that all dogs learn differently. These different learning styles will need to be adjuted for by the person working directly with the dog and training may not be able to play out exactly as suggested on the paper.