Worming medicine makes horse manure toxic to earthworms?

Larry London (london@calypso.oit.unc.edu)
Wed, 16 Feb 1994 11:01:24 -0500 (EST)

How widespread is the use of Zimectrin (or other medicines possibly
toxic to earthworms) at riding/boarding stables? Will this render
organic growers using horse manure ineligible for organic certification
or worse yet will this seriously affect earthworm populations in their
garden soil?

london@sunsite.unc.edu
-

From: jmcnult@orion.it.luc.edu (John A. Mcnulty)
Newsgroups: sci.agriculture
Subject: Horse manure, Zimectrin, and earthworms
Date: 16 Feb 1994 13:48:40 GMT

I have been following a thread in rec.equestrian on outlawing
horse manure in California as "toxic waste", and one in
rec.gardens on the commonly used de-wormer Zimectrin as being
toxic to earthworms. If horse manure is mixed with urine/wood
shavings bedding, won't the decomposition of the shavings
require extra nitrogen, thereby negating the urine problem?

Are de-wormers fatal to earthworms (makes sense!) and how long
does the stuff last in compost?

Patty, not John