Wisconsin Cranberry IPM Newsletter, Vol. 8, Iss. 9, September 5, 1994

              

Wisconsin
Cranberry IPM
newsletter volume .1, lumber 9, september s, 1994
Integrated Pest Management for Cranberries
FATE OF PESTICIDES IN THE
ENVIRONMENT
The fate of a pesticide in the environment
begins with its initial distribution and continues
through its subsequent movement and persistence
in each component of the environment.
Distribution may begin when you apply a
pesticide to the target area. Studies have shown
that a significant percentage of pesticides never
reach the intended site of application because of
drib, volatility, or misapplication.
A pesticide can move from the target area in a
variety of ways. It may'
* Volatilize from plant or soil surfaces,
* Be moved by wind or water from treated
foliage to the soil,
a Be carried laterally by surface water l'tmofl| or
through soil erosion,
* Be incorporated into the soil with crop
residues,
@ Be taken,from the site as residue on
transplants or harvested fruit, or
* Leach through the soil.
Eventually, a large portion of many pesticides
we apply ends up in the soil. lf the soil does not
have a chance to break down pesticides before it
leaches through the soil profile or is washed away
on the soil surface, the pesticides we apply may
ultimately contaminate surface waters or
groundwater.
Many factors determine the extent of pollution
which is likely to result from the use of a given
pesticide. Pesticides vary in their degree of
attachment or adsorption to soil particles. Those
which are strongly adsorbed are less likely to be
carried from the treated area by surface water or
to leach through the soil into the groundwater;
they may, however, be moved readily by soil
erosion. Pesticides also vary in their degree of
water solubility; obviously, those with greater
solubility have a greater potential for both
movement and water contamination. The
volatility of a pesticide is a measure of its
tendency to turn into a vapor. Pesticides with
greater volatility dissipate more rapidly and pose
less risk of soil and/or water pollution.
An often-critical favor in determining the
extent of pollution is the rate of degradation or
breakdown of the pesticide; pesticides vary
substantially in their susceptibility to degradation.
Degradation may be chemical, physical,
biological, or any combination of the three.
Biological breakdown of a pesticide results from
attack by fungi, bacteria and other
microorganisms. While most degradation of
pesticides occurs in the soil, breakdown also may
occur in water or on soil or plant surfaces.
Biological activity in the soil and its subsequent
eject on the rate of pesticide degradation depend
upon adequate soil moisture and temperature.
When a pesticide is degraded, it is changed
chemically', it is usually, but not always, broken
down into nontoxic compounds. A1l pesticides,
including the chlorinated hydrocarbons, are
subject to degradation; only the rate of
degradation varies. Although some pesticides
may remain in the environment for years, none
will remain forever. Once degradation has
proceeded to a juiciest extent, most pesticides
are no longer active and pose no further risks of
pollution.