Pesticides and the Environment

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Pesticides and the Environment

• ASM 336

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Pesticides

• Goal to stop or limit pest occurrence
• Types
• Insecticides kill insects
• Herbicides kill weeds
• Fungicides suppress or kill fungi

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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.

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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.

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Pathways of pesticide movement

• Runoff
• Chemical degradation
• Volatilize (gas vapor)
• Leaching and breakdown in soil
• Leaching and degradation by microbes
• Photo degradation (sun)

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Factors influencing a pesticides fate

• Properties of the pesticide
• Conditions where when applied
• Application method

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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

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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.

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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).

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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.

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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.

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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.

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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.

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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