Effects of pesticide in the environment

1. Pesticides and the
Environment
ASM 336

2. Pesticides
• Goal: to stop or limit pest occurrence
• Types:
– Insecticides – kill insects
– Herbicides – kill weeds
– Fungicides – suppress or kill fungi

3. Benefits
• Allow agricultural producers to improve the
quality, quantity, and diversity of our food
supply.
• Used in timber, turf, horticulture, aquatic,
and structural pest control industries.
• Homeowners and home gardeners often
use pesticides in their homes, yards, and
on pets.

4. What Happens after Application?
• When pesticides are applied the goal is that they
will remain in the target area long enough to
control a specific pest and then degrade into
harmless compounds without contaminating the
environment.
• Once applied, many pesticides are mobile in the
environment (air, soil, water).
• This movement can be beneficial (moving
pesticide to target area, such as roots) but can
also reduce the effect on the target pest and
injure nontarget plants and animals.

5. Pathways of pesticide movement
• Runoff
• Chemical degradation
• Volatilize (gas vapor)
• Leaching and breakdown in soil
• Leaching and degradation by microbes
• Photo degradation (sun)

6. Factors influencing a pesticide’s fate
• Properties of the pesticide
• Conditions where & when applied
• Application method

7. Properties of the pesticide
• Vapor Pressure (volatility) – pesticides
with a high vp are more likely to change to
a gas and escape into the atmosphere.
• Sorption – attraction to soil surfaces,
pesticides with higher sorption values
have reduced leaching

8. Properties of the pesticide
• Water Solubility/dissolvability - more
soluble pesticides have lower sorption and
are more mobile in the environment as
they are leached or moved with runoff.
• Persistence – the amount of time a
pesticide remains in the environment,
measured by half-life. Pesticides with
longer half-lives pose a greater threat to
the environment.

9. Conditions where & when applied
To maximize pesticide effectiveness and
minimize negative environmental impacts,
the pesticide must be compatible with the
physical, chemical, and biological
conditions of the application site.
• For pesticides use in crop or plant pest
control consider the following conditions:
• Soil: physical and chemical properties
(texture, amount of organic matter, pH).

10. Conditions where & when applied
• Geology – depth to water table (larger distances
give more soil to act as filter)
• Surrounding water sources – nearby water is
more susceptible to contamination when
pesticides are applied to highly erodible soils,
over-irrigated, or rain-soaked soils. Managing
crop residues and maintaining grass waterways
and filter strips help to protect surface waters
from sediment and pesticide pollution.

11. Conditions where & when applied
• Environmental conditions – heavy or sustained
rainfall or irrigation shortly after pesticide
application can increase runoff, leaching, and
volatilization.
• Soil temperatures (extremely high or low) can
interfere with pesticide performance. Pesticides
generally become more volatile in high
temperatures and windy weather.
• Pesticides can be incorporated (disked in) or
applied directly into the soil to decrease the
potential for drift and volatilization.

12. Application method
The challenge for pesticide applicators is to
maximize the benefits of pesticides through
sound management while reducing
environmental risks. This includes:
• Keeping current of the latest information.
• Taking all necessary preventive measures,
including transportation, secure storage, proper
disposal of containers and rinsate, and spill
prevention. Furthermore, avoid sensitive areas
such as sinkholes, depressions, wells, surface
water, public institutions and private buildings.

13. Product labels
• The pesticide label is a binding, legal
document. Compliance is required by state
and federal regulations.
• Label directions must be carefully followed
– from purchase to container disposal.
• High risk pesticides may only be
purchased and applied by certified
persons.

14. Pesticide Use
• Careful selection for a specific pest –
understand the pest, site, product, and
risks.
• Careful and responsible use.
…shows a consideration for the
environment.
….responsible stewardship
Acknowledgement: WQ-19
By B. Joern, B. Lohman, and F. Whitford