before choosing a compost method)
it safe to use compost from yard wastes that have come in contact
with pesticides, or other toxic chemicals? The major route of
breakdown of pesticides is through microbial degradation, which
is the process
of decomposition. Any pesticide a homeowner can buy without a
license will be broken down in the compost pile before the end
of the process.
The one exception to this is clopyralid, which is contained in
certain Dow products. Confront is the product that homeowners
might use. This is a long lasting herbicide, and vegetation that
been treated with this should NOT be composted, since the resulting
compost can cause serious injury to sensitive crops.
typical home yard chemicals, and their reaction to composting:
bait: Most commercial slug baits contain metaldehyde which,
when exposed to water, quickly breaks down to a harmless alcohol.
(Fresh metaldehyde is toxic to slugs, snails, birds, cats, dogs,
raccoons, rabbits, and humans).
Herbicides: Some herbicides become harmless in a very short time
in the soil and compost piles (such as Diquat, Paraquat). Others
(such as 2,4-D and propanil) break down in compost piles, but only
after thorough composting. Still others (such as arsenic, borate,
picloram, simazine, sodium chlorate) are extremely long-lived and
will probably survive most composting processes. Do not use organic
matter in your compost pile if it was treated with long-lived herbicides,
such as CONFRONT.
Insecticides: All contemporary insecticides will break down during
the decomposition process. Old chlorinated hydrocarbon insecticides
such as DDT (which has been banned for a long time) may survive.
Fungicides: Vegetation that has been just sprayed with a fungicide
may suppress the development of decomposing fungi if it is added
to the compost pile. A few weeks will degrade the fungicide enough
so that it will not effect the decomposition process. Currently,
one turf fungicide, PMA, contains mercury and may only be used by
commercial pesticide operators. This should not be used.
not use pressure
treated wood to construct compost bins. It is now well
demonstrated that chemical components of the pesticide do leach
from treated lumber. The compost may retain a good share of those
chemicals, and some would be carried with water into the soil or
drains below. This could affect the compost’s quality, as well
as safety and performance.