September 20, 2014

1 - Roaches are common inhabitants of compost piles, but there are several ways to manage them to keep them out of your home.

Yard and Garden September 20, 2014


I have a compose pile that has been neglected for months. I have been just piling the veggies and fruits. I have added hardly any dirt, so the pile is about a foot high. I went yesterday to dig a bigger hole to bury the stuff and saw that there were some cock roaches in that pile. Without thinking to get advice from you I dug a bigger hole and buried all the stuff including the roaches. I got to thinking about it and is there something I can use to kill the roaches without damaging the compost? What can I do at this point? I found a few roaches around the outside of my house; I think this is where they are coming from even though they are a little ways in my back yard. Help!

-Helen M.


A neglected compost pile will continue make compost, but more slowly than one that is managed to work optimally. The main things needed for composting to continue are undecomposed organic materials (kitchen scraps) and moisture. Moisture is often the most limiting factor in many New Mexico compost piles. The soil is not critical, but may help maintain moisture in the pile and perhaps seal-in objectionable odors if they are present. A well maintained compost pile should not have unpleasant odors a few feet from the pile.

Insects are a common element in compost piles. They are part of the process of making compost. Roaches can be part of the composting process, but most people do not like to have roaches near their homes. Roaches are common in parts of New Mexico with warm winters. The compost pile may be attractive to roaches, drawing them away from your home. If the compost is far enough away from the house, it may not create a problem. However, if you wish to treat the compost, diatomaceous earth may help manage the roaches. Diatomaceous earth is composed of the broken silica (glass) shells of sea algae (diatoms). This material cuts the skin of soft bodied insects and causes them to dry out. It will not harm your compost.

Another option is to collect your finished compost and pasteurize it with heat. In this manner you allow the insects to help with the composting process. Do this only if the compost is not allowing the roaches and other insects to invade your home. A pesticide barrier outside your home may also help with this. This barrier may be an organic or non-organic product used according to its label directions. Heat pasteurization may be done in an oven, on a barbeque, or by solarization (using solar energy). Heating in an oven inside creates unpleasant odors indoors and may bring the roaches you do not want into your home. Solarization means covering the finished compost with clear plastic, sealing the edges with soil, and letting the sun raise the temperature of the compost to adequate temperatures to kill the insects, diseases, and weed seeds that have survived the composting process. The necessary temperature is 140 to180 degrees Fahrenheit. Maintain this temperature throughout the compost mass for at least 30 minutes. The higher temperatures are recommended if there are weed seeds present in the compost. You can measure the temperature with a soil thermometer (if it can reach these temperatures), or a meat thermometer (never again used with food). Press the thermometer stem through the plastic to the bottom of the pile of compost. The thicker the layer of compost, the longer it will take to reach pasteurization temperatures.

Pasteurization is the process of heating a substance enough to kill diseases, insects, and weed seeds, but not high enough to kill some beneficial organisms. Sterilization to kill all organisms allows potentially harmful organisms to reestablish while pasteurization leaves beneficial organisms present. After pasteurization, the beneficial organisms rapidly colonize the pasteurized material and prevent recolonization by diseases.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email:, office: 505-865-7340, ext. 113.


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