Toxicity of Turfgrass Chemicals to Earthworms
Edited by Laurie Weiss, Former Commercial Horticulture Agent for Milwaukee County

At a recent talk, Dr. Chris Williamson, UW-Extension Entomologist, gave some interesting research data on the toxicity of various lawn chemicals to earthworms, generally considered beneficial in our home lawn situations because they break up compaction, turn over soil and break down thatch. These results are summarized from a research paper.>

Toxicity  Level

Herbicides

Fungicides

Insecticides

Plant Growth
Regulators
Colored line

No 
Significant 
Toxicity

Dicamba

Chlorothalonil 

Azariractin 

Flurprimidol 

Dithiopyr 

Iprodione 

Bifenthrin 

Melfuide

Isoxaben

Cyproconazole

Cyfluthrin

-

Pendimethalin

Fenarimol

Endomopathic

-

Prodiamine

Fosetyl-AL 

Nematodes

-

Triclopyr

Iprodione

Fluvalinate

-

-

Metalaxyl 

Isofenphos

-

-

Propiconazole

RH5849

-
Colored line

Moderate Toxicity  
(25-50% reduction)

-

-

Clorpyrifos
(Dursban)

-

-

-

Diazinon

-

-

-

Trichlofon
(Dylox / Proxol)

-
Colored line

Severe Toxicity
(75-100% reduction)

-

Benomyl (Benlate) 

Bendiocarb (Turcam)

-

-

Thiophante-methyl
(Cleary's 3336WP)

Carbaryl (Sevinol,
Sevin)

-

-

-

Ethoprop (Mocap)

-

-

-

Fonophos (Crusade)

-
Colored line

This data was generated existing by Daniel A. Potter, University of Kentucky.