California Department of Resources Recycling and Recovery (CalRecycle) 

Organic Materials Management

Compost Pile Microbes

The process of decomposition is a very complex but natural one. There are many organisms that create the breakdown of organic matter. Most are not seen by the human eye, but they are there throughout the process. Others that are large enough to see are usually associated with the later breakdown stages.

Something Got You Bugged?

So you've been working on your compost pile for eight months and figure it's time to harvest and use some of that "good stuff" you've been making.  So out you go to your compost bin and you find ... BUGS!!! What do you do now?

First, don't panic! Not all bugs are bad. In fact, all bugs play a role in nature. Many compost pile organisms eat other organisms and turn them into compost. At least one-third of the volume in a compost pile is made up of the dead, decomposed bodies of soil organisms.

Still, you don't want just any old bugs in your compost pile. So lets learn about what you might find in your compost pile so you'll be able to decide whether there really is a problem or not.

The Compost Food Web

If you are just trying composting for the first time, you may be surprised by the size and complexity of the community of small organisms that take up residence in your compost pile. These organisms, which include many insects, bugs, slugs, bacteria, and fungi, form what is called a "food web." In the food web, each organism has a job to do in turning your organic waste into dark, crumbly finished compost.

The food web decomposition process is divided into three levels:

  • Level One (primary consumers) is comprised of the organisms that shred organic matter and the microscopic organisms that eat the shredded organic residues.
  • Level Two (secondary consumers) is comprised of the organisms that eat level one organisms.
  • Level Three (tertiary consumers) is comprised of the organisms that eat level two organisms.

Maintaining the Balance

All members of the compost food web are very beneficial to your compost pile and should be left alone to do their work. They need each other to survive. If you remove any of the member organisms through the use of insecticides, you will interfere with their natural cycle as well as contaminate your compost with insecticide residues. While the organisms are busy recovering from the imbalance created in their food web, your compost pile will be decomposing much slower. On the other hand, if you are willing to closely monitor the temperature in your compost pile, you can speed up the process by gathering excess sow bugs, earwigs and slugs and adding them to your pile after it has cooled.

The "Great Escape" Issue

Home composters often fear that the hungry organisms in the compost pile may escape to the garden or lawn and eat everything in sight. Fortunately, this is not the case. The compost pile is their preferred environment. In fact, other organisms from the garden or lawn may leave their homes and go into the compost pile!

However, if you are concerned about the food web in your compost pile "breaking out," try the following tips:

  1. Create a barrier by spreading a line of wood ash (not barbecue ash because of fat residues) or crushed egg shells around your compost pile. This will keep the activity contained within the pile.
  2. A similar, but more lethal technique, is to sink small margarine containers full of stale beer, molasses and water, or yeast and water in the ground around the compost pile. Unsuspecting slugs, sow bugs, and earwigs will be attracted to the liquid, crawl inside, and drown.

Of course, some bugs and insects may overpopulate parts of your garden. If this is the case, try the following solutions.

Flies
Compost piles made entirely from yard trimmings do not usually attract flying insect pests in large numbers. So if you have flies, particularly fruit flies, you're probably putting food waste too close to the surface in your pile or you are including meat or dairy products, or even animal manure. Flies can be greatly reduced by keeping meat, dairy, and manure out of the pile. Also, you should bury all the plant food waste in the center of the pile and cover the top of the pile with a one-inch layer of soil, dry leaves, or finished compost. Ensure that the pile is not too damp or too acidic by maintaining a balance of materials. You could also compost your food waste in a worm bin or just bury them under 8- to 10-inches of soil.

Earwigs
If you discover earwigs on your plants, there are two solutions. Earwigs can be trapped in rolled up newspaper, old hose, or corrugated cardboard and shaken into the compost pile. Another solution would be to simply spray the offending earwigs with a solution of one tablespoon of liquid soap detergent combined with one quart of water. This will kill the earwigs that are doing damage and spare the helpful bugs that are eating dead organic material.

Home Composting

Last updated: June 7, 2012
Organic Materials Management http://www.calrecycle.ca.gov/Organics/
Contacts: http://www.calrecycle.ca.gov/Organics/Contacts.htm