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Thursday, April 30, 2015

Prevent Roaches from Mulches Entering the Home

Q. I know you recommend bark mulches around trees to help in water retention. However, there are negatives to consider such as cockroaches, bugs, etc.  I encounter lots of cockroaches in the ground when I have excavated in certain areas of our yard.

Untreated wood chip mulch including pine needles and leaves
A. I encourage the use of wood mulches more than bark mulches. Bark mulches seldom decompose much and add very little value to the soil. They are purely decorative. Wood mulches decompose easily in moist soils and add a lot of value to desert soils.

Benefits of wood chip mulch

You are absolutely right. Insects such as cockroaches are scavengers. Like many insects they like two things; water and a food source. This is why you frequently see tons of them inside irrigation boxes.

They feed on plants and animal life that have died and help in its decomposition. Feeding on dead and animal life helps return organic life back to the soil.

Cockroaches do not discriminate between dead plant or animal life whether it is inside the home or outside the home. They will enter the home if given the opportunity.

Using a foundation spray

Using a foundation spray or pesticide around the perimeter of the home and in valve boxes helps to keep them from entering our home. This is an insecticide spray barrier applied to the outside of the home at soil level and 12 inches above the soil. A good time to make this application is when temperatures begin to cool in the fall.

 It also helps if you keep wood mulches away from the foundation of the home. There is no reason you need to apply wood mulches up to the foundation.


  1. Looks like you misstyped in the first paragraph of your answer meaning Wood mulches decompose

    1. Right you are! I corrected it and it now reads correctly. Thank you!

  2. I too am a huge believer in the benefits of wood chip mulch in the arid desert home yard. I would hate to see anyone not practice this important method to improve their soil through increased moisture retention and water infiltration, increase air space, increase available carbon and nitrogen, lower salts, root cooling, lower soil compaction, decreased need for fertilizer and others I am forgetting.

    So I recommend increasing the barriers for cockroaches must pass through to get inside your home. I installed security doors on my home and besides that purpose it noticeably both lowered my electricity and gas costs (presumably it kept wind from forcing its way inside) and dramatically reduced the insects found within my home.

    While I find cockroach nymphs inside my house fairly frequently say three times a week, I doubt I see more than one adult every three months. A puff from the bug spray kills them within 20 minutes.

    There are other methods (see links below). Remember bugs generally do not want to be inside your home any more than you want them there. It is a foreign environment to them. Sometimes it is appealing because it is cooler or warmer than outside, but most of the time it is an accidental exploration that is not working out to well for either party.

    Also remember if you kill of their predators you will see an increased presence of roaches including within the home. I remember when I was in high school I once went out at night and killed every black widow I found all around the home's foundation. About three dozen all together; hanging in their web transfixed in my flashlight unaware the impending smash of my thong. They were all dead withing five nights. Roaches and crickets invaded the house like never before within a couple of weeks.

    Cockroaches: The Environmentally Friendly Pest Control Series—No. 1

    How to bug-proof your home:

    Cockroach Management

    Identification of Common Landscape Pests and Beneficial Organisms in Nevada

  3. I mostly find rol-y pol-ys (pill bugs) in my wood mulch. My biggest concern, though, is whether or not it's a fire hazard. It's kept away from the foundation of our home, but with a "postage-stamp" back-yard orchard, I'm never sure if 15-20 feet is far enough. I tend to wet it all down during July fireworks, for instance...