Chapter 8: Right-of-way Environmental and Personal Safety Concerns

Backflash

The uptake of herbicide by untreated trees adjacent to treated trees

Back-Siphoning

The accidental movement of liquid pesticide back through the fill hose and into the water source (also called back flow)

Biofilter

An untreated area of vegetation between a treated area and a sensitive area such as a steam or crop

Biotype

A weed within a given species that has a slightly different but distinct genetic makeup from other weeds of the same species

Degradation

The breakdown or decomposition of a pesticide or other substance. May be through several processes including biological (microbial), chemical (hydrolysis), or uv light (photodegradation)

Groundwater

Water beneath the surface of the earth in soil or rock. It often collects in pore spaces among silt, sand, gravel, or rock

Herbicide resistance

The inherited ability of a plant to survive an herbicide application to which the natural or wild type is susceptible

Herbicide tolerance

The inherited ability of a species to survive following an herbicide treatment

Non point source pollution

Contamination that comes from a wide, or diffuse area

Phytotoxicity

A toxic effect by a compound (usually on herbicide or growth regulator) on normal plant growth

Persistence

The ability of a pesticide to remain as an effective residue because of low mobility and chemical stability; long-lasting

Point source pollution

Contamination that comes from a specific identification place or point (e.g ditch, pipe, gully etc)

Recharge

Inflow of surface water to a groundwater reservoir that maintains the water level in that reservoir

Residual control

The ability of an herbicide to remain active and control weeds effectively for a certain period following application

Venturi effect

The reduction in fluid pressure that results when a fluid flows through a constricted section of pipe

Viscosity

The resistance of fluid to flow

Environmental changes

Pesticides are just one group of many chemicals blamed, sometimes unfairly for environmental abuses by the public and activists

- up to you to understand how pesticides enter into, retained in, affect, and degrade in the environment so that you can reasonably and accurately address public concerns

Pesticide faith

- it enter the environment where it enters various ecological-compartments through movement, distribution, persistence in soil, and eventual degradation by biological, chemical, and physical processes,

- much of the pesticide you apply may never reach its intended destination

Pesticide movement and residual control

- wind or water may transport it from foliage to soil or may volatilize from plant or soil's surfaces during warm weather

- leach through the soil laterally by surface runoff or through soil erosion by wind or rain

- eventually, much of the pesticide we apply ends up in soil and trace amounts may find their way into surface water or ground water

A pesticide's persistence

- a measure of how long it remains in an active form

- depends on the pesticide's adsorption, solubility, and eventual degradation

- can be good or bad thing it may provide long-term control or become a harmful residue and damage non target plants

- most herbicides used in right-of-way do not persist in animals

Degradation

- beneficial process that removes pesticide residues from the environment

- microbial degradation, photodegradation, and chemical degradation

- microorganisms in the soil consume pesticide, breaking them down into less toxic or non toxic forms

microbial degradation works best when the soil is warm, moist, aerated, and fertile

Degradation cont`

- in photodegradation, sunlight, primarily high energy UV-B light rays, gradually breaks down chemical bonds within the pesticide changing it into less toxic and non-toxic residues

- when a pesticide degrades it changes chemically it usually, but not always immediately breaks down into nontoxic compounds

- no pesticide last forever

Drift

- airborne movement of a pesticide beyond the target site. occurs when small spray particles vapors, or both are carried on air currents off the target site

- may kill nontarget plants, cause health and environmental effects, and property damage

- most troublesome and costly problem facing you as a commercial applicator

Drift cont,

The most common reason that drift occurs is applicator error

- drift can occur hours or even days later

- typically occurs during or shortly after the pesticide is applied when wind or application equipment blows the pesticide off the intended site

- volatilization of herbicide can occur

Types of pesticide drift

off target movement of pesticide can be in the form of spray droplet drift, vapor drift, and particle or dust drift

Spray drift

off target movement of pesticide during liquid application. Result of small spray droplets being carried off site by air movement

- occurs more frequently because almost all spray applications result in some off target movement

- adding drift reduction agents can help reduce drift

- spray at low pressure, use tips with narrow discharge angles, use largest practical nozzle diameters, use additives, and spray during the calmest parts of the day avoiding temperature inversions

Vapor drift

formulated as low-volatility product (good)

movement of pesticide as gaseous vapors from the target area

- some pesticides can change from a solid or liquid into gas

- occurs with high temperatures and low humidity levels. vapor or gas may drift further and for a longer time

- as air temperature increase and humidity decreases the likelihood that pesticides will volatilize, and drift increases

Particle drift

The movement of solid particles from the target area by air during or just after an application

- particles formulated as dusts or the smallest of granules that are nearly the size of dust or soil particles which pesticides are attached

- some pesticides can remain action on soil particles for long periods. If particles are blown off the target area, contamination or damage to sensitive areas can occur

Factors influencing pesticide drift

- can be influence by spray solution characteristics, the weather, the application equipment, and the applicator's decisions

Droplet size

The number one factor influencing drift is droplet size. Small droplets do not have enough mass to drop quickly, so they remain airborne which reduces their mass even further

- large droplets will fall faster and be less exposed to wind and evaporation

- the higher a droplet is released and the stronger the wind, the greater the chance that a droplet will travel downwind and drift

- have a balance between increased drift from small droplets and decreased coverage from larger droplets

Pesticide formulation

The viscosity of a liquid is a measure of its resistance to flow and thus affects droplet size

- as the viscosity of a pesticide mixture increases, so does the droplet size, thus reducing the potential for off target movement

- invert emulsions aid in reducing drift

- invert emulsions have less water loss, and more of the pesticide reaches the target

Drift control agents

- adjuvants and application systems can help overcome drift

- drift control additives, foams, high viscosity invert systems

- added to the spray mixture to increase the viscosity of spray solution, reducing the number of small droplets

- the best management practices to minimize drift potential are to correctly manage nozzle types, height of application, and operating pressure

- foams/invert emulsions

Foams (drift control agent)

foam generating systems involve the use of an adjuvant with a specially designed air expansion nozzle, which combines tree to four parts of air to one part of spray mixture to form a "wet foam". results in large heavy viscous spray particles

Invert emulsion (drift control agent)

a water in oil preparation with oil being the larger part of the mixture as opposed to the standard oil in water emulsion

- heavier droplets than foam or stabilized by spray additives

Wind speed (weather)

- wind speed most important factor influencing drift

- high wind speeds will move droplets down wind and deposit them off target

- dead calm conditions not recommended because of inversions

- drift potential is lowest a wind speeds between 3 and 10 mph blowing away from sensitive areas

Wind direction (weather)

- influence where off target spray droplets will be deposited

- apply pesticide whenever the wind is blowing away from sensitive areas

Air temperature and relative humidity (weather)

high air temperature and low humidity go hand in hand in creating a worst case scenario for pesticide drift

- caution when relative humidity is at below 50% and when temperature is high

- drift is most likely during the hottest part of day

- hot conditions reduce droplet size

Temperature inversions (weather)

A condition that exists when the air at ground level is cooler than the temperature of the air above it

- conductive to pesticide drift

- occurs early morning or evening hours

- drifts that occurs over a long distances often the result of temperature inversions

- early morning and evening best time to apply pesticides

application equipment (nozzle selection)

- select the best nozzle type

- superior droplet size characteristics

- low drift designs

- drift reduction nozzles to create large droplets at the same flow rate and operating pressure as comparable standard-flat fan nozzlees

- nozzles are cheap compared to cost of materials and litigation cost

Boom/nozzle configuration and spray height (application equipment)

- for ground sprayers, keep the boom close to the target in accordance with the nozzles being used

- do not spray at greater heights than those recommended

- the spray release height will influence how far droplets will travel downwind

- nozzles with wider spray angles allow lower boom heights

Spray pressure (application equipment)

- use lowest possible spray pressure

- pressure is an ineffective way to increase coverage and canopy penetration

- increasing pressure is not an efficient method to make significant increases in output volume

- changing to a nozzle tip with a larger orifice is most practical

Carrier volumes (application equipment)

Although some product labels require low volumes there are others that you may select with a higher volume that allows the use of larger nozzles, which produces larger, less drift prone droplets when operated at the correct pressure

Application speed (application equipment)

- higher speeds are not only harder on your equipment and difficult to maintain but also result in enough air movement to cause some drift

- increasing operating speeds can cause the spray to be diverted back up into upward wind currents and vortexes behind the sprayer, trap small droplets and contribute to drift

Applicator decisions (application equipment)

- applicator's job to determine the critical factor and to take precautions against it

- must recognize sensitive areas around each site before starting application

- use judgement to minimize chances of drift by regarding equipment and weather factors

Volatility

The evaporation and movement of pesticide vapors after application

- liquid to gas/problem like drift

- choose amine formulations when possible

- spray during coolest part of day

- avoid high temperatures and low humidity

- stone and asphalt surfaces have relatively greater potential for volatility

Lateral movement

- the displacement of herbicide across the soil surface in flowing water, often called runoff

- compaction caused by road construction encourages surface water flow

- beware of heavy rains, steep slopes, saturated soils

- light rains more likely to move herbicide in soil reduce lateral movement

- all soil active herbicides can move laterally

Leaching

- movement of herbicides with water downward through the soil

- factors that affect leaching: soil's qualities, herbicide' water solubility, residual and adsorption properties of the herbicide, type and amount of precipitation

- if an herbicide is strongly adsorbed to soil particles it is less likely to leach

- leaching is more common in sandy soils

The amount of water

- too little water may fail to move the herbicide into the root zone of target plants

- too much water may contaminate the root zone of nontarget plants with herbicide

- excess water may also carry the herbicide past the root zone of target plants

Brownout

Discoloration of plant foliage after an herbicide application

- can become a serious public relation problem

- unsightly contrast to surrounding green vegetation

- do late season treatments, dormant basal treatments

- use products that do not cause rapid foliage discoloration

- apply late in brush growing season to blend with developing fall color

Backflash

Uptake of herbicide by untreated trees adjacent to treated trees

- occasionally occur between unrelated species

- noticed where affected trees are located out of the treated area but show similar effects to the treated treees

Livestock

Johnson grass becomes more attractive to livestock after spray, it produces prussic acid or cyanide that can kill animals

- animals can ingest herbicide residue from treated plants

- the herbicide could be an illegal residue in the meat or milk, thus restricting the sale of these products

Roadside loading and mixing

Loading along roadside is hazardous because of potential for contamination when taking water from creeks and ditches

- have a backflow device to avoid back-siphoning

- maintain a air gap

- use reduced pressure backflow prevention device

- install a double check valve assembly in filler hose

Roadside mixing and loading cont

- use a nurse tank which never carries chemicals, on a second vehicle

- do not mix or load next to an open water source

- do not discard empty containers/triple rinse them emptying rinsate into tank

- close chemical containers immediately after each use

Mechanical safety

safety rules for machines

- good fit operator clothes

- first aid kit

- tractor with safety devices

- properly ballasted tractor

- be alert of obstructions

- avoid sudden starts, stops

- short frequent breaks are better than longer, less frequent ones. if you are exhausted stop

Dealing with pesticide spills

you must clean up any spills that happen

- quicker you contain, absorb, and dispose of a spill, the less chance there is that it will cause harm

- wear ppe

- control, contain, clean up (3cs)

- control actively spilling chemicals, contain the spilled material, and clean up.

do not leave spill unattended

Herbicide resistance

Influenced by spray coverage application method, herbicide rate, environmental conditions

- herbicide tolerance is the inherent ability of a species to survive following an herbicide treatment

- if simply possess a natural tolerance

Herbicide resistance cont

Herbicide resistance is different from tolerance and is the inherited ability of a plant to survive an herbicide application to which the natural or wild type-plant is susceptible

- small numbers of herbicide resistance individuals occur in plant population

- herbicides select for herbicide resistant individuals by controlling susceptible plants

Biological factors behind resistance

- herbicide is sequestered in cell vacuole

- weed is capable of metabolizing herbicide

- herbicide depends on binding to an enzyme for toxic effect

- herbicide is not absorbed into the weed

Herbicide factors

Several herbicide families act on only a single site of action within a plant. They are more likely to select for resistant weeds because a change in only one gene may be enough to affect an herbicide's binding potential

- herbicide with multiple action sites are beneficial

Managing herbicide resistance

- Products were constantly switched back in the day

- today herbicides tend to be more complex, difficult to manufacture and expensive to develop/use

- assume weeds can develop resistance

- Use integrated vegetation management plan

- use herbicides only when needed

- apply herbicides at proper rate

- rotate herbicides with different modes of action

- keep accurate records

Differences in preception

- answer property owners questions and respond to their concerns clearly and directly

- view as opportunity to educate public

- know the answer to questions before they are asked

Carelessness

Often problems of pesticide application are best resolved by improving operational practices

- most problems are within control

- misuses related to the actual application usually are due to carelessness

- follow the label and use common sense