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Jeffrey from Hauula, Hawaii writes

How to treat inside hollow concrete block walls for roaches. Beach house in Hawaii on ocean.

I have tried everything, even tented the house but the enamel paint on the walls prevented penetration of gas. Place is clean, tight, no garbage problems, and I have used powders in attic and interior walls, built on slab. They have moisture from the ocean and humidity, and food might be old dead comrades in the walls. This has been going on for years and in summer they come out in numbers and die on floor...stink up the place, seem to stay inside walls mostly during rest of year. I am thinking of drilling holes at intervals and putting a cap in the hole for treatment access. Have caulked many gaps, still have a few trim boards to do. Spray(cedar oil) and worse stuff and gel every 3 months, exterior granules and spray. Roaches not infesting inside house, come out of walls and die on floor...scares the vacation renters. What can I put in these walls that will fume the voids? I am afraid to let up on the treatments and have not tried stuff that gets carried back into the walls...they die before they can return. Need a roach expert guru opinion.


There is not a product that can create a fog within the wall voids. Using an insecticide dust such as Delta Dust is the longest lasting treatment for voids since the formulation is very stable. This dust is also moisture resistant. You can use residual sprays along baseboards and baits in cracks and crevices up high. You can also place glue boards in areas where you have seen activity to better identify what kind of roaches you are seeing so that you can better tailor your treatment.

Answer last updated on: 06/05/2014

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