Soil Insect Killers

Soil Contents

• Decaying organic matter in soil is the source of energy and nutrients for garden vegetables and ornamental plants. Humus is the portion of organic matter that is already decomposed. Active organic matter is partially decomposed and is the portion that feeds insects and microorganisms. Oribatid mites are tiny insects that chew and shred the active organic matter in soil, releasing its nutrients to be cycled through new plants. Many species of soil mites also eat fungi, algae, snow fleas and dead springtails.

Soil Insects

• Oribatid and other soil mites depend on other organisms to create tunnels to move through in the soil. They move through and live in the spaces between soil particles, called aggregates. Insect and microorganism activity is often centered on the root system of plants growing in soil, cycling nutrients through their bodies and into the plants. Sowbugs are a vital insect in the soil food web. Their powerful mouth parts are used to fragment plant residues and assist in the decomposition process.

Predator Insects

• Species of centipedes, spiders, ground-beetles, rove-beetles and gamasid mites feed on a broad range of harmful garden soil pests that cause plant disease. Killing these types of soil insects with pesticides, synthetic fertilizer, monoculture planting and excessive tilling increases the presence of disease-producing organisms. Soil health and vegetable plant health depends on a wide diversity of insects and microorganisms. Populations of essential beneficial bacteria and fungi also decline when predator insects decline.

Harmful Agricultural Practices

• Synthetic fertilizer relies on high nitrogen content to stimulate plant growth, but it may also disrupt soil insect communities. High levels of nitrogen stimulate the growth of harmful soil insects such as chinch bugs, as well as pathogenic fungi. Some yard and garden chemicals and heavy applications of fertilizer kill earthworms and other beneficial organisms, which slows the essential creation of organic matter in the soil. Practices such as maintaining a wide diversity of plants, making backyard compost and adding mulch create a healthy environment for insects and other contributors to soil health.