Pesticides and Earthworms

Preservation of a healthy earthworm population is important for thatch and compaction management in turfgrass systems. When insect, disease, or weed problems occur and a pesticide application is deemed necessary, it is important to select products that have the least detrimental effect on earthworm populations. Some pesticides can cause severe and long-term reductions in earthworm numbers. Most earthworm species grow slowly, live for several years, and have low reproductive rates. Earthworm populations may take many months or years to recover following intentional or non-intentional pesticide applications that reduce worm populations.

To reduce detrimental effects of pesticide use on earthworm populations in lawns:

1. Apply pesticides only when needed; eliminate preventive applications whenever possible.

2. Use spot applications of pesticides.

3. Select products that are least injurious to earthworms and do not exceed labeled rates.

4. Avoid pesticide applications when earthworms are near the soil surface (soon after a rain or irrigation).