Insects, Bugs and Slugs
The process of decomposition in your compost pile is a very complex, but natural one. Living organisms digest the organic matter in the pile. If you are just trying composting for the first time, you may be surprised by 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. Many have the job of eating other organisms and turning them into compost. In your finished compost, at least one-third of the volume is made up of the dead, decomposed bodies of soil organisms.
The food web is divided into three levels as shown on the attached diagram. The roles of the organisms, at each stage of the decomposition process, are explained below.
Who lives in the food web?
The most productive members of your compost pile's food web are the bacteria. Every piece of organic matter you place in the pile is covered with varying amounts of bacteria as they digest the organic material and break it down into its basic elements. While digesting, they are also reproducing at an incredible rate. One gram of bacteria can become about 450 grams of bacteria in only three hours. There are many kinds of specialized bacteria operating in different temperature ranges.
Psychrophilic bacteria work best in temperatures of about 13 degrees C (55 degrees F), but can stay on the job even in below freezing conditions. This is why you will notice your compost pile sinking in the winter; these bacteria are busy breaking down organic matter. As these cooler bacteria go to work, their activity actually begins to heat up the pile. The increased temperature creates the ideal conditions for the next type of bacteria to arrive.
Mesophilic bacteria work best in temperatures of about 21 degrees C to 32 degrees C (70 degrees F to 90 degrees F), but can stay on the job in even hotter conditions. The activity of mesophilic bacteria can heat the pile up to even greater temperatures of 43 degrees C (110 degrees F). Thermophilic bacteria become active when the temperatures reach a range of 40 degrees to 93 degrees C (104 degrees F to 200 degrees F). If you notice your compost pile steaming in the morning or on a frosty day, it's because these bacteria are busy at work, decomposing your organic waste. These bacteria generally last for up to five days, and then the pile begins to cool.
Actinomycetes go to work next. These fine, gray-coloured strands are a cross between the bacteria and fungi that often excrete vitamins and antibiotics as they consume the organic waste in your pile.
Molds and fungi get down to business along with the actinomycetes. They are closely followed by the members of the food web that shock many a new composter. These are small mites, springtails (little insects that hop like fleas), beetles, centipedes, sow (pill) bugs, flies, slugs and earwigs. The slugs, sow bugs, earwigs and beetles all excrete "castings" that are very dark and fine, like those of earthworms.
Worms also arrive at this stage. Unlike the other small and "scary" creatures, worms are generally welcomed by new composters. As a result of the worm's well-deserved reputation for being excellent decomposers, many people think that it's a great idea to add extra worms to their compost pile. This is unnecessary. Let the worms find their own way into the pile, when the conditions are right. They prefer the pile when it is cooler, so adding worms could lead to their quick demise in the hot, steamy pile.
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 and contaminate your compost. 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.
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:
- Create a barrier by spreading a line of wood ash (not barbecue ash) or crushed egg shells around your compost pile. This will keep the activity contained within the pile.
- 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.
Don't get bugged!
Some bugs and insects may overpopulate parts of your garden. If this is the case, try the following solutions.
Earwigs
If you discover earwigs on your plants, simply spray the offending ones with a solution of one tablespoon of liquid soap detergent combined with a litre of water. This will kill the earwigs that are doing damage and spare the helpful bugs that are eating dead organic material. Earwigs can also be trapped in rolled up newspaper, old hose or corrugated cardboard and shaken into the compost pile.
Flies
Flies, particularly fruit flies, can be greatly reduced in the compost pile by burying all food waste in the centre of the pile and covering the top of the pile with a 2.5-centimetre (1-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.
Read on...
If you are interested in learning more about the compost food web, the following books will help:
- Tiny Game Hunting, H.D. Klein and A.M. Wenner
- Bugs, Slugs and Other Thugs, R.H. Massingham Hart
- Ecological Gardening, M. Harris
- How to Get Your Lawn and Garden Off Drugs, C. Rubin (available from Harbour Publishing)
- The Bug Book, H. and J. Philbrick (available from Garden Way Publishing)
- Rodale's Colour Handbook of Garden Insects (available from Rodale Press)