We have an outside deck with many cockroaches under it. What can we use to get rid of them? 

American Cockroach –Periplaneta americana This is generally the cockroach that people in our area see running around at night and sometimes in the daylight if disturbed. It seems they get called ‘water bugs’ quite often because their nature habitat is moist or damp areas. Under a deck will supply a great habitat. Generally, lots of leaves, shady and damp.

The following are answers from several Parker County Master Gardeners.

1. Mix Boric acid and anything that will draw them in like sugar

2. My thoughts on this:  boric acid and powdered sugar mixed together and placed in crawl spaces and around doors etc. I saw it in the paper several years ago. Sugar attracts them, boric acid kills them. 

3. This is from the University of Florida “Dusts”:  Indoors, non-organic dusts, such as silica gel and boric acid can be placed in out of the way cracks and crevices. Can be applied with a bulbous type duster under sinks, stoves, refrigerators, behind baseboards, in electrical outlets and in cabinet cracks. Silica gel is finely ground glass or sand that rubs the protective waxes off the cockroach cuticle resulting in dehydration. Cockroaches walking across the boric acid pick up the dust on the sticky cuticle. As they groom off the boric acid dust they ingest it into their stomach and it kills them

4. Take horse apples (these are the large rough, green apple-like fruit of the Bois d’Arc tree) in the fall and place them by outside doors and around the foundation of the home and the roaches won’t come in. Use whole apples, will need to be replaced each year. They don’t smell.

5. We just mix a little sugar with boric acid. We use it to also get rid of ants. A tablespoon of boric acid with about 1/2 teaspoon of sugar placed in a shallow container on the floor. We keep one in the RV. 
Please try one of the above methods because they are affective and safe to use. 

You can also treat with chemicals (find the large plastic containers with the tubing and sprayer attached). You can also call a professional exterminator to do the job but we recommend the above methods first.