Insecticide sprays Bnd paint barriers Applied to the surface of extruded polystyrene, and different types of insulation, were evaluated for prevention of lesser melllwonn, Alphitobius diapcn"nlls (Panzer), infestations. In a lahoratOly study, tetrachlOlvinphos 50 ¥lP and pirimiphosmethyl 7E on extruded polystyrene produced> 90% mortality in larval and adult lesser mealwonn populations 71 wk after application. These insecticide spray treatments, however, were not effective under conditions found in the manure pit of a high rise cage layer house. Our field study showed that Styrofoam SS"" and Ethafoarn 220''', were resistant. to lesser mealwonn infestations. Super IQ'" paint., a latex paint impregnated with chlorpyrifos, was also effective in protecting extruded polystyrene from infestations under field conditions.