Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as 

Non-biodegradable substances like pesticide residues cannot be digested or consumed by organisms, so, they are just passed on to organisms of next trophic level along with food. These non-biodegradable residues keep on accumulating. This phenomenon is called as biomagnification

Higher the trophic level an organism occupies in the food chain higher will be the accumulation of non-biodegradable pesticide residues.