Control of American cockroaches (Dictyoptera: Blattidae) in sewers

Baits, dusts, and aqueous sprays were applied to sewer shafts to control American cockroaches, Periplaneta americana (L). Boric acid and hydramethylnon baits failed to provide consistent control because of problems with mold on the baits and because large populations of cockroaches depleted the bait. Bendiocarb, boric acid powder, and a powder mixture of silica gel + synergized pyrethrins provided excellent control for at least 1 mo, but cockroaches reinfested treated shafts within 3-6 mo. Treatments made in the fall when adult cockroach populations were lowest (about 26%) provided best results. Aqueous sprays of wettable powder chlorpyrifos and microencapsulated diazinon provided outstanding control for at least 9 mo. Microencapsulated and emulsifiable concentrate chlorpyrifos sprays provided greater than 94% reductions for a year.