a method for applying a barrier to structures to prevent the infiltration of pest species uses a composition formed from a polyurethane polymer system and a pellet comprising a pesticide incorporated into a sorbent and dispersed in the polyurethane polymer system . the composition protects the structure by application either to the structure or to a pathway that leads to the structure . advantageous polymer systems include polyurethanes rich in urea linkages and predominating in aliphatic and alicyclic backbones .