Chapter 5
Protecting the Environment
Air, water, and land are interconnected, and pesticides applied to reach
target organisms also may reach fish, wildlife, plants, livestock, beneficial
insects, and nearby people. This Chapter describes potential unintended
effects of pesticides on the environment, pesticide movement in the
environment, and successful strategies to protect the environment when
applying pesticides.
Improving water quality and habitat is a priority among Minnesotans, as evidenced by the
passing of the Clean Water, Land and Legacy amendment to the state constitution in 2008.
Photo: Natural Resources Conservation Service (NRCS)
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Notes Page
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Section 1: The Pesticide
Applicator’s Environment
Environmental protection laws and pesticide label directions are designed
to prevent health and environmental problems caused by pesticides. In
addition to knowing the law and following label directions, pesticide
applicators should understand what can happen when pesticides applied to
eliminate targeted pests end up in places these chemicals don’t belong. This
Section discusses the range of “environments”—natural and manmade—
that applicators encounter, and how they can be adversely affected by
pesticides.
Learning Objectives:
1. Give an example of a situation in which pesticides have unintended
consequences on air, water, or soil.
2. Discuss pesticide characteristics that affect the pesticide’s
environmental fate.
3. Discuss environmental factors that can affect pesticides’ fate.
4. Identify three kinds of “sensitive sites” that may be harmed by a
pesticide application.
Terms to Know:
wAdsorption
w Biomagnification
w Break-down products
wDrift
w Food chain
wHalf-life
wPersistence
wSolubility
w Temperature inversion
w Vapor pressure
wVolatility
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Pesticide Use and the Environment
Pesticide applications cannot be safely undertaken without an understanding of the interconnections among air, water, land, and the life they
support. By understanding these environmental connections, pesticide
applicators can better manage target pests while minimizing harm to the
environment.
Air
When pesticides are applied, they may be carried off-site in the air as
spray droplets, vapors, solid particles, or even treated soil particles. The
physical movement of pesticide spray droplets through the air, at the time
of or soon after the pesticide application, to any site other than the intended
site is known as pesticide drift. Pesticides applied in windy or dead calm
conditions (during a temperature inversion) can move off-site and harm
humans, animals, and the environment.
Brisk Wind, Unintended Consequences
Soybean aphids are a target organism
for chlorpyrifos pesticides.
Photo: University of Minnesota
Chlorpyrifos pesticides are used to control soybean
aphids and spider mites on soybeans. In August
2009, chlorpyrifos was being applied to a central
Minnesota soybean field, despite wind speeds of 9-15
mph, gusting up to 17-23 mph. The label specifically
prohibited application in winds in excess of 10 miles
per hour.
The insecticide drifted onto a residential property.
Apple trees and vegetables on the property were
sampled, and chlorpyrifos contamination was
documented. The Minnesota Department of
Agriculture (MDA) cited application violations:
the label prohibited application when wind speed
was greater than 10 mph, there was off-site drift
and damage (contamination) of the apple trees and
vegetables. MDA issued a financial penalty.
By applying pesticides when the weather is
consistent with label directions, off-site drift can be
minimized.
Water
Pesticides are monitored in lakes, rivers, streams, groundwater, and rain
by the Minnesota Department of Agriculture’s water quality program.
The majority of these detections are at very low levels. However, a few
pesticides have been detected at levels approaching or exceeding water
quality benchmarks set for protection of humans or aquatic organisms.
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As pesticides move through the ground, microorganisms in the soil
can break down the pesticide into other chemicals. Pesticides can also
be broken down by sunlight, naturally occurring chemicals in the soil,
and by plants. Most of these break-down products are less toxic to the
environment than the original pesticide, but some can be more toxic.
Land
Land consists of different types of soil (such as sand, clay, or silt) often
layered on top of one another, underlying or exposed rock formations, and
groundwater. Pesticides properly applied to the land surface as directed by
the label usually stay there until they break down into inactive compounds.
Problems arise when surface runoff carries pesticides into lakes, streams,
and wetlands; or water percolating through the soil carries pesticides down
to groundwater. Pesticides with a long effective half-life break down slowly
and may move to a location where they could harm plants, insects, animals,
or bacteria.
Harvested Ditch Hay, Unintended Consequences
A newly planted soybean field in the Lamberton area showed severe signs
of herbicide damage. There had been no recent application of a broadleaf
herbicide in that field, but manure had been applied in the spring. Tracing
back, the manure was from horses that were fed ditch hay treated with
picloram, a broadleaf herbicide used in rights-of-way.
Further investigation revealed harvest restrictions on the picloram product
label. The label warns that if the harvest and grazing restrictions are not
followed, the product may carry through to the manure and urine of animals
fed picloram-treated plants. Picloram in the manure caused the soybean
damage, which occurred because the label was not followed.
Always follow label grazing and harvest restrictions for herbicides that
carry over into manure and urine.
Pesticide Fate in the Environment
Several processes affect the fate of pesticides in the environment. These
include the way pesticides move in air, water, or soil after they are applied
(transportation) and how they change after interacting with the soil, plants,
or sunlight (transformation).
Herbicides move from ditch
hay to horse manure to a
struggling soybean crop.
Photo: NRCS
Among the ways that pesticides can be transported are:
w Spray drift – during application, pesticides in spray droplets can
be shifted by the wind from the location where they were applied to
another location.
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w Volatilization – pesticides can evaporate into the air and then the
vapors may move on the wind.
w Runoff – pesticides can run off the land during rainfall, snowmelt,
or irrigation.
w Leaching – pesticides can percolate through the soil into
groundwater.
w Adsorption – pesticides can attach to soil and then move when soil
is eroded by water or wind.
Transformation often involves the process of decomposition, when the
original pesticide chemistry is transformed into a different, usually less
complex, chemistry. As the break-down process progresses, the original
pesticide disappears from the environment and is replaced by a series of
break-down products, also called degradates. Pesticides can be transformed
by:
w Plant uptake – plants can take up pesticides from the soil.
w Photodecomposition – sunlight can break down pesticides.
w Microbial decomposition – microorganisms in the soil can break
down pesticides into different chemical compounds.
w Chemical degradation – over time, the soil’s chemistry can break
down or change as bonds between molecules creating new
compounds.
Precipitation
Photo
degradation
Evaporation/Volatilization
Pesticide
spray
Drift
Surface run
off /
ero
sio
n
Soil surface
Root zone
Plant
uptake (absorption)
Degradation
Runoff
Degradation
Percolation/Leaching
Surface water
Water table
Groundwater
Fate of pesticides in the environment. Adapted from the University of Illinois General Standards manual.
Pesticide Properties That Affect Its Environmental
Fate
Pesticides’ chemical properties affect not only how effective they are,
but also how they may move, persist, or break down in the environment.
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Breakdown of pesticides in the environment
19th Edition
In other words, a pesticide’s specific properties affect its fate in the
environment.
Pesticides that are volatile (evaporate readily at normal temperatures and
pressures) are more likely to end up drifting to non-target areas.
Pesticides that have high solubility (the amount of a substance that will
dissolve in a given amount of another substance, such as water, at a
specified temperature and pressure) are more likely to end up in surface
water. Highly soluble pesticides can mix as easily with rain as with the
water used to dilute them to the appropriate application strength. Pesticides
with high solubility also percolate into groundwater more rapidly than less
soluble compounds.
Note:
Information about a
pesticide’s soil halflife is often found in
the Materials Data
Safety Sheet (MSDS)
for the product.
Pesticides with high adsorption (that adhere in an extremely thin layer of
molecules to the surfaces of soil or sediment particles) stick with the soil
and stay in the environment longer.
Pesticides with a long soil half-life (the time required for half the
amount of a substance introduced into a living system or ecosystem to be
eliminated or disintegrated by natural processes) stay in the soil long after
one or many treatments. Over time the pesticide concentration can actually
build up in the soil.
Environmental Factors that Affect Pesticide Fate
Weather conditions have a major impact on pesticide fate. Rain, snowmelt,
wind, humidity, temperature, sunlight, and temperature inversion all
influence how pesticides are transported or transformed.
w Temperature inversions occur when the layer of air at ground
level is colder than air higher up—the opposite of normal air
temperatures. Inversions are very stable and create “dead calm.”
Spray droplets from pesticides applied during inversions can stay in
a concentrated cloud and move slowly toward sensitive plants and
animals.
w Temperature increases make pesticides more volatile and may
cause pesticides to move as a vapor to non-target sites and harm
sensitive plants and animals. That is why some pesticide labels
restrict application over a certain temperature.
Soil properties can influence how quickly chemical pesticides break down
or move from the application location.
w Organic matter and clay particles in the soil are good at tying up
(adsorbing) pesticides to their surfaces so the pesticide is no longer
available in the soil. This is why some pesticides labels have higher
application rates on soils high in organic matter or clay: to ensure
effectiveness. When adsorbed to the surface of organic matter and
clay particles, pesticides are prevented from moving to contaminate
groundwater or surface water. Organic matter in soils also contains
nutrients that nourish micro-organisms that naturally break down
pesticides.
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w Soil texture and porosity also influence pesticide fate. Soils that are
“tight,” such as those with lots of clay, have the benefit of preventing
leaching, and so pesticides are not likely to reach groundwater. But
such soils also allow for greater pesticide volatilization and surface
runoff. Water moves rapidly through soils that are “coarse textured,”
such as sandy or gravelly soil, increasing the chance of pesticides
leaching to groundwater, but preventing surface runoff.
Finally, a soil that is steeply sloped allows dissolved pesticides to run off
more rapidly than soils on flat or gently sloping lands.
The diagram below shows the breakdown of pesticides in the environment.
Photodegradation
Microbial degradation
Chemical
degradation
(hydrolysis)
Chemical degradation
Breakdown of pesticides in the
environment.
National Pesticide Applicator
Certification Core Manual.
Adapted from OSU Pesticides
and Groundwater Contamination.
Pesticide Impacts on Ecosystems
An ecosystem is formed by the interaction of a community of organisms
with their environment. When a pesticide is introduced, it can disrupt an
ecosystem in a number of ways:
w It repels, controls, or kills the target pest The target pest, however,
may be food for another organism. If the target pest is the major
food source for a local bird species, the unintended outcome of
killing the pest may be reducing the bird population.
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w A pesticide that effectively kills a target organism may also
effectively kill a beneficial species. Insecticides that kill wasps in a
barn, for example, may also kill a hive of bees needed to pollinate
fruit trees.
w Pesticides can accumulate through the food chain. As multiple
small organisms are eaten by larger ones, pesticides found in the
smaller organisms can build up in the tissues of the larger one.
Biomagnification is a process whereby some organisms accumulate
chemical residues in higher concentrations than those found in the
organisms they consume.
DDT Concentration
(parts per million)
Biomagnification in the food chain. Adapted from Penn. State Pesticide Education Manual.
Biomagnification in Loons: Unintended Consequences
Common loons were studied to assess the biomagnification of persistent contaminants in lake ecosystems
in Atlantic Canada. Forty-two breeding adults and 20 juvenile loons were captured in August 1995–1997
on lakes in New Brunswick and Nova Scotia. Plasma samples from adult loons were analyzed for PCB and
organochlorine pesticides. Loons from one of the four sites had higher levels of PCBs, DDE, oxychlordane,
trans-nonachlor, mirex, and hexachlorobenzene. The higher pesticide levels in the loons are attributed to the
biomagnification of these pesticides found in their food supply.
Biomagnification is known
to occur in Minnesota’s
state bird, the Common
Loon. Photo: National
Parks Service
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Sensitive Sites
Pesticide applicators exercise caution at any treatment location, but certain
sensitive sites require greater planning and care. As the name indicates,
sensitive sites are more susceptible to negative side effects that pesticides
may have. Sensitive sites include:
w Areas producing organic crops or livestock. Products certified
as “organic” are required to be grown free from most man-made
pesticides for three or more years. Applying a pesticide not
approved for organic production that ends up in the soil, water, or
groundwater of an organic operation could have major economic
and legal consequences.
w Lawns and gardens. Drift minimization is especially important
here. Children and pets play on lawns. People of all ages and states
of health eat food grown in gardens.
w Lakes, rivers, and wetlands. Many pesticides are toxic to fish and
other aquatic organisms, including aquatic plants that form the base
of the food chain. Minimize drift, leaching, and runoff.
w Parks and protected natural areas. Parks and natural areas
contain high-value environmental resources, including threatened
or endangered species. It is illegal to harm an endangered or
threatened species, or to destroy or modify its critical habitat, when
using a pesticide. Protect people in these areas, too, by observing
safe application methods.
Parks and protected
natural areas, such as
Aquatic Management
Areas (AMAs) and
Sensitive Natural Areas
(SNAs) contain high value
species and ecosystems.
Photo: NRCS
w Drinking water supplies. We all need safe drinking water.
Applicators should know if a treatment site has any wells or is
within a wellhead protection area (area around a well from which
drinking water is drawn). Most at risk are shallow wells, abandoned
or broken wells that may be hidden, and wells located in very
permeable soil.
w Municipal drinking water well fields. Location and depth of
municipal drinking water wells is an important consideration.
Check with the local municipal water supplier if there is any
possibility that the treatment site may be within a wellhead
protection area. This is not always easy to determine without
consulting the municipal water supplier.
w Waste management areas. Bacteria play an essential role in
breaking down wastes in compost and manure treatment facilities,
and pesticides can interfere with or kill beneficial bacteria. In
addition, finished compost and re-applied manure are both recycled
into the food supply.
w Air intake systems. Airborne pesticides that drift into an air intake
system can be rapidly distributed throughout a building.
w Daycares, schools, senior facilities, or health-care facilities.
These sensitive sites are likely to house children, the elderly, or
people with health issues, all of whom may be more sensitive to
pesticides than healthy adults.
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The applicator who is aware of the potential harm to living things that
depend on clean air, water, and land can take steps to minimize any
unintended effects of pesticides. The next Section describes strategies to
help the pesticide applicator to protect the environment.
Section 2: Preventing Impacts of
Pesticides on the Environment
Pesticides that move from a treatment site to nearby air, water, or land can
have unintended adverse effects on living things. Applicators can prevent
harm to the environment by understanding how pesticides move from
treatment sites to locations where they might cause environmental damage
or harm.
Learning Objectives:
1. Name five pesticides that have best management practices (BMPs)
developed for them by the Minnesota Department of Agriculture.
2. Know who is legally liable for damage caused by pesticide drift.
3. Name at least three of the factors that affect the droplet size of an
applied pesticide.
4. Describe what benefits a vegetative buffer zone has in preventing
impacts of pesticides on non-target sites and organisms.
Terms to Know:
w Application setback
w Best management practices (BMPs)
w Karst geology
w Non-point source pollution
w Vegetative buffer
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Protecting Water
The Minnesota Department of Agriculture (MDA) and other agencies
monitoring water quality have sometimes found pesticides in Minnesota’s
surface and groundwater. By preventing “point source” water
contamination that comes from places where pesticides are stored, mixed,
or loaded into application equipment, applicators can protect our water
resources. Preventing “non-point source” contamination that occurs when
a pesticide runs off the soil surface or leaches through the soil profile, is
just as important.
Pesticide applicators can do many things to protect Minnesota’s waters.
Minnesota’s Pesticide Management Plan spells out pollution prevention
strategies that applicators can follow.
Minnesota ranks
number one in fishing
licenses per capita, and
the state places a high
priority on clean rivers,
lakes, and streams.
Minnesota’s Pesticide Management Plan
Minnesota law requires the state to have a Pesticide Management Plan
for the protection of groundwater and surface water. This plan calls for
monitoring for pesticides and, if they are found, developing appropriate
response plans. Most importantly, this plan focuses on preventing
pesticides—and their break-down products—from reaching Minnesota’s
water resources.
To reach this goal, the Pesticide Management Plan requires the MDA
to develop Best Management Practices (BMPs). BMPs are practical,
research-based ways for users of pesticides to prevent or minimize surface
water and groundwater contamination. BMPs reduce water contamination
by helping applicators properly:
w
w
w
w
w
w
120
Store pesticides;
Transport pesticides;
Mix and load pesticides into application equipment;
Apply pesticides;
Manage pesticide waste; and
Develop incident response plans for pesticide leaks, spills,
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The Pesticide Management Plan established a process for the MDA
to develop water-quality BMPs for pesticides commonly detected in
groundwater or present at levels of concern in surface water. These BMPs
will reduce water contamination that may result from the normal, legal
use of pesticides. The BMPs are voluntary unless they reference label
requirements. As always, read and follow label directions.
Minnesota currently has core water quality BMPs for all agricultural
herbicides and specific BMPs for these five herbicides:
wAcetochlor,
wAlachlor,
wAtrazine,
w Metolachlor, and
wMetribuzin.
Pesticide applicators using agricultural herbicides should understand
and implement water quality BMPs whenever possible to protect water
resources and avoid additional requirements. Under the Pesticide
Management Plan, Minnesota may impose pesticide-use restrictions if
voluntary BMPs do not keep water contamination from a specific pesticide
within water quality standards.
To learn more about the Pesticide Management Plan or to review current
BMPs, see the MDA’s pesticide management website information at www.
mda.state.mn.us/pesticides.
Find fact sheets describing water quality BMPs for herbicides on the MDA
website at www.mda.state.mn.us/herbicidebmps.
The MDA has developed an electronic distribution list (e-mail listserv) to
communicate via e-mail about MDA activity related to pesticide non-point
source water quality issues. To subscribe to the MDA Pesticide Non-Point
Source electronic distribution list, go to the following website and follow
the instructions for signing up to receive e-mail updates: http://webmail.
mnet.state.mn.us/mailman/listinfo/mda-pesticide-non-point-source.
Surface Water
Surface water includes the lakes, rivers, streams, ponds, ditches, and
wetlands with which Minnesota is richly endowed. Following application,
pesticides can move into surface water in several ways, including through:
w Surface water runoff. Runoff from hard surfaces, such as
pavement and compacted soil, travels faster and transports more
pesticide than runoff from surfaces that absorb water.
w Tile drainage. Tile systems and their surface tile intakes can
transport pesticides from the land to surface waters.
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w Air deposition. Pesticides can enter surface water as spray drift,
from movement of volatized pesticides or from the deposition of
airborne dust.
Pesticides that have high solubility are more likely to end up in surface
water and groundwater because, once they are dissolved in water, they can
go wherever water goes.
Application Setbacks and Vegetative Filter Strips
Two recommended BMPs for protecting surface water are application
setbacks (also called application buffer zones) and vegetative filter strips
(also called vegetative buffer strips).
An application setback is created when the pesticide applicator leaves
distance between an area treated with a pesticide and an associated
sensitive area, such as surface water in need of protection. Application
setbacks reduce the possibility of a pesticide drifting into the sensitive area
during application or entering the sensitive area after application in field
runoff.
A vegetative buffer or filter strip is an area of permanent close-growing
vegetation over which field runoff passes before entering surface water.
Vegetative filter strips trap pesticides running off treated locations before
they reach surface water. Filter strips often are located on the field edge
adjacent to water bodies, but can also be located within the field in the form
of a grassed waterway.
Some product labels require mandatory application setbacks or vegetative
filter strips to protect water quality.
Grassed waterways
trap pesticides and
prevent runoff to
surface water.
Photo: NRCS
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Examples of pesticides with labels requiring mandatory application
setbacks are the herbicide atrazine and the pyrethroid family of
insecticides. At this writing, atrazine requires a 66-foot application setback
from points where field runoff enters streams or rivers and a 200-foot
application setback from the water edge of lakes. Pyrethroid insecticides
currently require a 25-foot application setback from the water edge of
aquatic habitats if ground applied and a 150-foot application setback if
aerially applied.
In addition to an application setback, pyrethroid insecticides require a 10foot-wide vegetative filter strip between the field edge and downgradient
aquatic habitats. Fact sheets to assist applicators with interpreting these
requirements on the atrazine and pyrethroid product labels can be found on
the MDA’s website.
Application setbacks and vegetative filter strips may be required on the
labels of other pesticide products. Read pesticide labels carefully to see
whether these practices are required.
Soil and water conservation district staff can be consulted for assistance on
the design and installation of vegetative filter strips, grassed waterways, and
other conservation practices that protect surface water.
Berm
el
d Runo f
f
Stre
am
or River
Fi
Minnesota Department of Agriculture graphic
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Groundwater
Seventy percent of Minnesota’s drinking water is obtained from groundwater. Pesticides can move into groundwater in a number of ways:
w With rain water, as it leaches through pesticide-treated soil.
w Through improperly constructed or abandoned wells that act like a
conduit between surface water and groundwater.
As noted in the previous section, pesticides with high solubility, low
adsorption, or a long half-life have a greater potential to move into
groundwater.
Pesticide applicators can avoid groundwater contamination by knowing site
conditions in advance, including:
w Permeability of soil. Water leaches more rapidly through a
“coarse-textured” soil (such as sandy soil) than through a “tight”
soil (such as clay-like soil). Information about soil permeability
can be obtained from the local soil and water conservation district
office.
w Depth to groundwater. The greater the depth to groundwater, the
more protected the groundwater is from pesticides leaching through
soil. Some product labels have application restrictions based on
depth to groundwater. The Minnesota Department of Agriculture’s
voluntary water quality BMPs recommend specific rates of
application on certain soil types to help protect groundwater.
Karst Geology: Sensitive Groundwater Resources in Southeastern Minnesota
Karst geology is one of Minnesota’s most interesting and well-studied environmental features. Karst forms on
soluble rock (frequently, but not always, limestone) that is worn down by water over time. Karst is characterized
by caves, sinkholes, a lack of surface drainage, and other climatically controlled features.
These characteristics
make southeastern
Minnesota water
resources challenging to
protect. Chemicals, such
as pesticides, used on the
landscape infiltrate rapidly
into groundwater and then
migrate, reappearing at
unexpected times and in
unexpected locations.
Know your farm’s
soils and geology.
Select pesticides and
application methods
that prevent groundand surface water
contamination.
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Preventing Drift
The EPA defines pesticide spray drift as the physical movement of
a pesticide through the air, at the time of or soon after the pesticide
application, to any site other than the intended site (often referred to as
an “off-target” site). Pesticide drift is not a new problem. However, with
increasing acreage planted to herbicide-resistant crops and a shift to more
post-emergence spraying, the potential for off-target drift damage has
increased. Drift can transport either particles or vapors through the air.
Particle drift occurs at the time of application, as small droplets and
particles of the spray solution suspended in air move to an off-target
location. Recent research has shown that all pesticides have the potential to
move via particle drift, and that particle drift is much more common than
vapor drift.
Vapor drift occurs when the pesticide changes from a liquid to a vapor, or
gaseous form, and then moves away from the treated area. Vapor drift can
occur both during and soon after application. Vapor drift is more common
with certain pesticides that are volatile (evaporate more readily). It is
possible with some pesticides that the chemical turns into a vapor after it
has been applied—sometimes even hours after application.
Distance Spray Drift Can Travel (3 mph Wind)
Droplet Size
Fog
Very Fine
Fine
Medium
Coarse
Fine Rain
Diameter (in
microns)
Time to Fall 10
Feet
Travel Distance
20
4.2 minutes
1,100 feet
5
100
240
400
1,000
66 minutes
3 miles
10 seconds
44 feet
6 seconds
2 seconds
1 second
28 feet
8.5 feet
4.7 feet
Source: Herbicide spray drift, North Dakota State University Extension.
Damage from pesticide drift can be significant. Drift to adjacent fields can
cause crop destruction or produce crops with pesticide residues so high
that they can’t be used or sold. Even long-established trees and ornamental
plants can be harmed. Fish and wildlife kills, including destruction of
desirable honeybees, can result from minimal off-target movement of some
pesticides, particularly insecticides.
Pesticide labels and laws are clear that off-target drift is illegal:
w State law specifies that pesticide applications must be performed
in a manner that does not endanger humans or damage agricultural
products, food, livestock, fish, or wildlife.
w State and federal laws require that pesticides must be applied in
a manner consistent with labeling. Since pesticide product labels
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almost always contain language that says “Do Not Allow This
Product to Drift,” or words to that effect, drift is a violation of state
law. Labels often give recommendations for minimizing pesticide
drift.
w Evidence that drift occurred is a violation of federal pesticide
control law.
w Minnesota has a strict liability legal standard for enforcement
of cases involving pesticide drift; if drift occurs, the applicator
is responsible. No proof of negligence, carelessness, or intent is
necessary for the MDA to bring an enforcement action against the
applicator.
w The applicator is responsible for pesticide drift damage.
The bottom line is that whether or not damage results, pesticide drift is
illegal and is not tolerated in the regulatory or agricultural community.
Drift also has non-financial consequences, and an incident of off-target
drift can incur hostility from neighbors, businesses, and other land owners
in the area.
Damage and concerns about pesticide drift are the most common types
of complaints reported to the MDA (for information about complaints,
see http://www.mda.state.mn.us/chemicals/pesticides/complaints.
aspx). Pesticide drift issues continue to be a national priority for the
U.S. Environmental Protection Agency, state departments of agriculture,
farm groups, industry organizations, advocacy groups, and the Extension
Service. Many complaints of pesticide drift are filed by farmers who
are frustrated and angered by the repeated and damaging drift from
neighboring farms. If farmers have or seek certification as an organic
producer, drift can destroy years of work and an entire crop.
Development of urban/suburban communities in formerly rural areas has
increased the potential for complaints about suspected damage. In urban/
suburban communities where residents aren’t familiar with pesticide use for
agricultural settings, residents often consider pesticide drift a threatening
“chemical trespass,” no matter what the actual risk or damage may be.
Although drift is by far the most common way for pesticides to move to
off-target locations, other ways that pesticides move through air include
volatilization and windblown contaminated soil particles.
Drift Prevention
Spray droplet size is the single biggest factor in determining whether a
pesticide will drift. Small droplets take longer to fall and can be carried
further by wind currents. Medium or large droplets fall faster and travel
much shorter distances. New technologies, such as drift-reduction nozzles
or spray additives that reduce drift, can be helpful in keeping pesticides on
the target site.
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ASAE1 Standard
Symbol
VF
Category
Very Fine
Comparative Size
Code
Red
Approx.
VMD2
<100
Relative Size
Comparative Size
Point of Needle
(25 microns)
Atomization
Fog
F
Fine
Orange
100–175
Human Hair
(100 microns)
Fine Mist
M
Medium
Yellow
175–250
Sewing Thread
(150 microns)
Fine Drizzle
C
Coarse
Blue
250–375
VC
Very
Coarse
Green
375–450
Staple
(420 microns)
Light Rain
EC
Extremely
Coarse
White
>450
#2 Pencil Lead
(2000 microns)
Thunderstorm
1American
Society of Agricultural Engineers.
Adapted
from
Bob Wolf, Wolf Consulting & Research, LLC
2Volume Median
Diameter.
Droplet size is a function of:
w Nozzle size. When selecting nozzles, consult the manufacturer’s
information on average droplet size under various pressures. If
possible, avoid nozzles that produce fine, very fine, or fog droplets
—those 200 microns or less—at the pressure you plan to use.
w Pressure. Higher application pressures create more small droplets
that are likely to drift.
w Boom heights. Calibrate application equipment to apply pesticides
at a lower boom height to decrease the distance that droplets travel
to reach the ground.
w Temperature and relative humidity. As the air temperature
increases and humidity decreases, droplets evaporate, become
smaller and lighter, and travel further.
After droplet size, wind speed and direction are the most important factors
affecting pesticide drift. Recording wind speed and direction (from which
the wind is blowing) for each application will help private applicators
document correct application if a drift complaint is filed.
Avoid spraying any pesticides when winds are greater than 10 mph. Know
the wind speed and direction at the time of application. Conditions reported
by local weather services vary greatly from conditions at the application
site. Measuring wind and temperature at the time and place of application
is best. New rigs may come with wind and temperature gauges. Otherwise,
a simple hand-held gauge is good.
1. Protecting
Integrated the
PestEnvironment
Management
Chapter 5.
Note:
If you need to
hire a commercial
pesticide applicator,
make sure that the
applicator follows
label directions,
too. Commercial
applicators are
required to give
you a copy of the
application record,
which must include
wind speed and
direction at the time
of application.
127
Although dead-calm conditions may seem ideal for pesticide application,
they may signal a temperature inversion. An inversion occurs when the
air close to the ground is colder than air higher up in the sky and air
doesn’t mix. Under inversions, the winds are very light to dead calm and
variable in direction. Pesticide sprays form small droplets (fines) that do
not fall out under inversion conditions. The pesticide fines can rise up until
they hit the warmer air layer. The pesticide cloud may drift horizontally
as a concentrated cloud for long distances. For this reason, do not apply
pesticides during temperature inversions.
As stated earlier, be especially careful near sensitive sites. If the wind is
blowing towards sensitive sites, even at low speeds, damage from drift may
occur. The best recommendation when applying pesticides near sensitive
sites is to spray when the wind is gentle (3-10 mph), steady, and blowing
away from high-risk areas. Sensitive sites can be protected by pesticide
applicators using application setbacks, also referred to as application buffer
zones—areas in which no pesticide is applied. If drift occurs despite every
effort on the applicator’s part, it will fall on the buffer zone rather than the
sensitive area adjoining the target site.
This farmer established a buffer zone between his fields and nearby sensitive water
resources. Photo: NRCS
To prevent drift, responsible and knowledgeable applicators set up and
calibrate application equipment with drift-reduction nozzles, lower pressure
settings, and lower boom heights to minimize drift. They check wind
speed, temperature, humidity, and conditions that signal inversions before
application. They establish buffers around sensitive sites or resources to
ensure that pesticides will stay on site and on target.
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PRIVATE PESTICIDE APPLICATOR TRAINING MANUAL
19th Edition
Section 3: Protected Species
Avoiding damage to non-target plants and animals is always the
responsibility of pesticide applicators, but that responsibility is all the
more critical when endangered or threatened species are concerned. In
this Section, pesticide applicators will learn about the federal Endangered
Species Act, Minnesota’s endangered species, and methods to check in
advance whether these species are within range of an area where pesticide
application is planned.
Learning Objectives:
1. Identify the three categories of endangered species covered in the
federal Endangered Species Act.
2. How does Minnesota’s endangered species statute differ from the
federal law?
3. Describe how you would find out what protected species are
located in the area in which you plan to apply pesticides.
Terms to Know:
w Candidate species
w Endangered species
w Threatened species
Prairie bush clover, a threatened species,
is found in agricultural areas of the state.
Photo: DNR
5. Integrated
Protecting the
Chapter 1.
PestEnvironment
Management
129
Endangered Species Act
Congress passed the federal Endangered Species Act in 1973 to stop further
extinction of plants and animals. The act defines endangered species as
a plant or animal in danger of extinction, and a threatened species as a
plant or animal likely to become endangered within the foreseeable future.
Candidate species—those that are in the process of being designated as
threatened or endangered—are also listed.
It is illegal under the Endangered Species Act to kill or harm an
endangered or threatened species. It is also illegal to destroy or modify
critical habitats on which they depend. Pesticide applicators should delay
or forgo pesticide application if protection of endangered or threatened
species cannot be ensured. There is no legal excuse for harming endangered
or threatened species or their crucial habitats with a pesticide. The U.S.
Fish and Wildlife Service (FWS) keeps the federal list of endangered,
threatened, and candidate species (see the table on page 131).
Minnesota Endangered Species
Statute and Rules
Minnesota also has an endangered species statute. The Minnesota
Department of Natural Resources (DNR) implements the Minnesota
Endangered Species Statute and related state rules. Minnesota has a
separate protection program and its own listings of endangered and
threatened species, as well as species of special concern.
Minnesota’s Endangered Species Statute prohibits killing, harming,
importing, transporting, or selling any part of a member of a species listed
by the state as being endangered or threatened. For more information, see
the DNR Web sites on endangered, threatened, and special concern species
(www.dnr.state.mn.us/ets/index.html and www.dnr.state.mn.us/rsg/
laws.html).
Through the work of the FWS, DNR, and MDA, landowners in Minnesota
generally know when an endangered, threatened, or candidate species is
living on their property. Pesticide applicators should check with landowners
about the presence of protected species before applying pesticides.
130
PRIVATE PESTICIDE APPLICATOR TRAINING MANUAL
19th Edition
Federally Listed Endangered, Threatened and Candidate Species in Minnesota
Plants
Leedy’s roseroot (Sedum integrifolium ssp.
leedyi)
Threatened
Cool, wet groundwaterfed limestone cliffs
Fillmore, Olmsted
Minnesota dwarf trout lily (Erythronium
propullans)
Endangered
Dakota, Goodhue, Rice, Steele
Prairie bush clover (Lespedeza leptostachya)
Threatened
North-facing slopes and
floodplains in deciduous
forest
Native prairie on welldrained soils
Brown, Cottonwood, Dakota,
Dodge, Goodhue, Jackson,
Martin, Mower, Olmsted,
Redwood, Renville, Rice, Rock
Western prairie fringed orchid (Platanthera
praeclara)
Threatened
Wet prairies and sedge
meadows
Clay, Kittson, Lincoln, Mower,
Nobles, Norman, Pennington,
Pipestone, Polk, Red Lake, Rock
Mammals
Canada lynx (Lynx canadensis)
Threatened
Northern forested areas
Aitkin, Beltrami, Carlton, Cass,
Clearwater, Cook, Itasca,
Koochiching, Lake, Lake of the
Woods, Marshall, Pine, Roseau,
St. Louis
Gray wolf (Canis lupus)
Threatened
Northern forested areas
Northeastern portion of the
state
Sandy beaches and
islands
Lake of the Woods, St. Louis
Wetlands and nearby
upland areas
Houston, Wabasha, Winona
Birds
Piping plover (Charadrius melodus)
Endangered
Reptiles
Eastern massasauga (Sistrurus catenatus
catenatus)
Candidate
Mussels
Higgins eye (Lampsilis Higginsi)
Endangered
Large rivers
Lower St. Croix River
Snuffbox (Epioblasma triquetra)
Candidate
Chisago and Washington
Spectaclecase (Cumberlandia monodonta)
Candidate
Small to medium creeks
and rivers
Medium rivers and
streams, large rivers
St. Croix River south of
Taylor’s Falls
Sheepnose (Plethobasus cyphyus)
Winged mapleleaf (Quadrula fragosa)
Candidate
Large rivers
Endangered
Lower St. Croix River
Large rivers
Main channel St. Croix River
Upland prairie
Western boundary of the state
Small rivers and
streams
Southwest corner of the state
Insects
Dakota skipper (Hesperia dacotae)
Karner blue butterfly
(Lycaedes melissa samuelus)
Candidate
Endangered
Sandy barrens and
savannas
Anoka, Winona
Fish
Topeka shiner (Notropis topeka)
Endangered
1. Protecting
Integrated the
PestEnvironment
Management
Chapter 5.
131
Steps to Protect Endangered Species
w Know the endangered, threatened and candidate species that live in
your area.
w Before applying pesticides on another person’s land, learn if a
protected species lives on the property being treated or on adjoining
land. For the most part, landowners know of the presence of
protected species from field work conducted by the Minnesota
Department of Natural Resources.
w Use strategies to prevent damage to non-target organisms, including
application setbacks, reduced rates, and application timing. Delay or
forgo pesticide application if protection of endangered or threatened
species cannot be ensured.
w Look for EPA Endangered Species Protection Statements when
reviewing pesticide labels.
w When an EPA Endangered Species Protection Statement appears
on a label, check to see if an EPA Endangered Species Protection
Bulletin exists for the county in which the pesticide will be used.
Call the telephone number or visit the website provided. The
bulletin is part of pesticide labeling—if one exists, you need to
obtain, read, and follow it.
w Obtain a new Endangered Species Protection Bulletin if the one
you have will be more than six months old on the day you apply the
pesticide.
Landowners and applicators can find out if federal or state listed
endangered, threatened, or candidate species are in the area. See the DNR
website at www.dnr.state.mn.us/rsg/index.html or call the DNR at (651)
296-6157 or (888) 646-6367. For more information, contact:
w U.S. Environmental Protection Agency
Endangered Species Protection Program
Office of Pesticide Programs
www.epa.gov/espp
(703) 305-5239
w U.S. Fish and Wildlife Service
Twin Cities Ecological Services Field Office
www.fws.gov/midwest/twincities
(612) 725-3548
w Minnesota Department of Natural Resources
Natural Heritage and Non-game Wildlife Research Program
http://www.dnr.state.mn.us/eco/nhnrp/index.html
(651) 259-5073
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PRIVATE PESTICIDE APPLICATOR TRAINING MANUAL
19th Edition