CORE Ch7 Cheat Sheet: Pesticides in the Environment

🎯 Top 5 Traps

1

4 PESTICIDE CHARACTERISTICS determine environmental fate: SOLUBILITY (high water solubility = more likely to MOVE in runoff/leaching); ADSORPTION (oil-soluble + positive-charged molecules bind tightly to clay + organic matter = LESS movement); PERSISTENCE (measured by HALF-LIFE — longer = more residue + more risk to nontarget organisms); VOLATILITY (turns into gas/vapor; INCREASES with heat + wind, DECREASES with humidity). 3 BREAKDOWN PROCESSES: CHEMICAL DEGRADATION (chemical reaction, often with water; no living organisms), MICROBIAL ACTION (soil fungi/bacteria), PHOTODEGRADATION (sunlight). Warm + wet speeds breakdown; cool + dry slows it.

2

3 DRIFT TYPES — and the conditions that create each. SPRAY DRIFT (most common) — small spray droplets on air currents; controlled by larger droplets (low pressure + bigger nozzle orifice), wind 3-10 mph, boom 20-24 inches above target, downwind buffers. WIND speed/direction = MOST IMPORTANT environmental factor. VAPOR DRIFT — volatile pesticides become gas in heat; many labels prohibit application above 85 degrees F; pesticides may volatilize HOURS after application. PARTICLE / DUST DRIFT — solid particles (dust formulations or pesticide-bound soil); reduce by closing windows/vents, turning off fans + forced-air systems. LARGE droplets drift LESS than small droplets, but may reduce coverage. Some drift control additives can actually INCREASE drift potential — follow the label.

3

TEMPERATURE INVERSIONS — the counterintuitive trap. Inversion = air at GROUND LEVEL is COOLER than air above. Air is STABLE: little or no vertical movement; almost all air movement is LATERAL. Small spray droplets get TRAPPED in the cool ground layer and travel LONG DISTANCES — more than 1 mile. Inversions develop in EARLY EVENING as ground cools and warm air has already risen; they intensify through the night and persist until MID-MORNING. Drift from an inversion may move long distances 1-3 HOURS after application. DETECTION: dust/smoke rises little and HANGS in the air; or a ground-level thermometer reads BELOW one elevated above the ground. Low-wind early evening + early morning conditions seem ideal — but if an inversion is present, they're the WORST time to spray.

4

POINT-SOURCE vs NONPOINT-SOURCE water contamination + leaching factors. POINT-SOURCE: specific identifiable location — pesticide spills entering storm sewers, BACK-SIPHONING into water supplies, surface water entering sinkholes, repeated spills at mixing/loading sites, careless wash water at cleanup sites, improper container disposal. NONPOINT-SOURCE: widespread area — runoff/leaching from broadcast applications. LEACHING is HIGHEST when: pesticide has HIGH solubility + LOW adsorption + HIGH persistence; soil is SANDY (fast percolation, fewer binding sites) + LOW in organic matter; water table is SHALLOW (less filter); geology is HIGHLY PERMEABLE (gravel). CLAY soil + HIGH organic matter slow leaching. GROUNDWATER provides 70% of US public/private water supply, irrigation, and industry. Once contaminated, correcting it is difficult or impossible.

5

Best Management Practices — operational rules. Mix and load AT LEAST 50 FEET from wells, lakes, streams, rivers, and storm drains. PREVENT BACK-SIPHONING with an AIR GAP between water hose discharge end and tank surface — air gap should be AT LEAST 2x THE DIAMETER of the discharge pipe; alternative: backflow prevention device or check valve. Bees travel UP TO 3 MILES from hive — apply insecticides EVENING OR NIGHT (early morning protects honey bees but wild bees forage at or before DAWN). NEVER apply insecticides to crops or weeds in BLOOM. GRANULAR formulations are particular hazard to BIRDS (mistake them for food/grit) — liquid formulations safer near wildlife. SECONDARY POISONING: predators eating poisoned prey. ENDANGERED SPECIES: consult county BULLETINS LIVE! before applying.

🔢 Numbers You Must Know

Number

What It Represents

4 pesticide characteristics

Solubility, adsorption, persistence, volatility — determine how a pesticide moves and behaves in the environment

3 breakdown processes

Chemical degradation (no living organisms — usually reaction with water); microbial action (soil fungi/bacteria); photodegradation (sunlight)

3 drift types

Spray drift (small droplets in air currents — most common); vapor drift (volatile pesticides as gas); particle/dust drift (solid particles or pesticide-bound soil)

3 to 10 mph

Recommended outdoor wind speed range for spraying. Higher = drift hazard. Very low (especially under inversions) may also produce extensive drift.

20 to 24 inches

Recommended boom height above target crop to reduce spray drift

50 feet

Minimum distance from wells, lakes, streams, rivers, and storm drains for mixing and loading

2x diameter of discharge pipe

Minimum AIR GAP between water hose discharge end and tank surface to prevent back-siphoning. Alternative: backflow prevention device or check valve.

70%

Share of US water (public + private supply, irrigation, industry) provided by groundwater. Once contaminated, hard or impossible to correct.

85 degrees F

Common pesticide label temperature cutoff above which application is prohibited (vapor drift risk for volatile pesticides). Pesticides may volatilize HOURS after application if temperature rises.

More than 1 mile

Drift distance possible under temperature inversion conditions. Inversion drift may occur 1 to 3 HOURS after application.

3 miles

Distance bees may travel from hive to find blooming flowers — notify beekeepers within this radius before applying bee-toxic pesticides

4 bee exposure routes

(1) Direct contact during foliar applications; (2) contact with residues on plant surfaces; (3) drift into hive entrance; (4) ingestion of residues in nectar, pollen, or guttation water

8 ASABE droplet categories

Standard S-572.1 droplet spectrum (with color codes): Extra Fine (Purple), Very Fine (Red), Fine (Orange), Medium (Yellow), Coarse (Blue), Very Coarse (Green), Extra Coarse (White), Ultra Coarse (Black)

Worst-case leaching profile

SANDY soil + LOW organic matter + SHALLOW water table + HIGHLY PERMEABLE geology = highest leaching risk. Pesticide: high solubility + low adsorption + high persistence.

🔀 Easily Confused

Pair / Group

Distinguishing Feature

Solubility vs Adsorption

Solubility: ability to dissolve in solvent (usually water). High water solubility = more likely to move with runoff or through soil. Adsorption: pesticide BINDS to soil particles. Oil-soluble pesticides + positive-charged molecules bind tightly to clay + organic matter. Tightly-adsorbed pesticides are LESS likely to move from spray site.

Persistence vs Volatility

Persistence: how long pesticide remains active in original form. Measured by HALF-LIFE — longer half-life = more persistent. May produce illegal residues on rotational crops. Volatility: tendency to turn into gas/vapor. Increases with TEMPERATURE + WIND, decreases with HUMIDITY.

Chemical vs Microbial vs Photodegradation

Chemical: NO living organisms — usually a chemical reaction with water. Microbial: soil microorganisms — fungi or bacteria. Photodegradation: reaction to sunlight. Warm + wet conditions speed up all three; cool + dry slow them down.

Drift vs Runoff vs Leaching

Drift: movement in AIR (spray, vapor, or particle). Runoff: movement in WATER over the SURFACE (off treated site). Leaching: movement in WATER DOWNWARD through soil to groundwater. Three different transport mechanisms.

Spray vs Vapor vs Particle drift

Spray drift: small spray DROPLETS on air currents — most common; control with droplet size, nozzle/pressure, wind 3-10 mph. Vapor drift: pesticides volatilized into GAS — hot weather; many labels prohibit above 85 degrees F. Particle drift: solid particles or pesticide-bound soil. Different conditions, different prevention.

Surface water vs Groundwater

Surface water: ditches, streams, rivers, ponds, lakes. Runoff from broadcast applications + erosion. Often a source of drinking water. Groundwater: water in saturated zone underground; reached by leaching. 70% of US water supply. Once contaminated, hard or impossible to fix.

Saturated zone vs Water table vs Aquifer

Saturated zone: layer of soil/sand/gravel/bedrock with all available spaces filled with water. Water table: BOUNDARY between saturated zone and overlying unsaturated rock/soil. Aquifer: overall geologic formation from which groundwater can be drawn. Different layers of the same vertical structure.

Point-source vs Nonpoint-source pollution

Point-source: SPECIFIC identifiable location — spills entering storm sewer, back-siphoning, sinkholes, repeated mixing/loading spills, careless wash water, container disposal. Nonpoint-source: WIDESPREAD area — runoff/leaching from broadcast applications. Typically blamed for outdoor environmental contamination, but point sources also significant.

Soil texture: Sand vs Clay/Silt

Sand: water moves FASTER; FEWER binding sites for pesticides; more prone to leaching. Clay/silt: smaller pore size; slower water movement; more binding sites; less prone to leaching (though leaching can still occur).

Organic matter: High vs Low

HIGH organic matter: greater soil ability to hold water + adsorb pesticides; pesticides more likely held in root zone (less leaching, more plant uptake). LOW organic matter: less binding capacity, more leaching risk.

Permeability: Highly permeable (gravel) vs Clay layers

Highly permeable (gravel deposits): water + dissolved pesticides move FREELY downward to groundwater. Clay layers: much LESS permeable — inhibit and slow downward water movement. Geology lying between soil surface and groundwater determines leaching speed.

Macropores

Cracks, worm holes, and root channels in soil through which small amounts of pesticide may move quickly downward. Distinct from porous flow through soil texture. Common pathway for fast leaching after heavy rain.

Bee timing: Honey bees vs Wild bees

HONEY BEES: forage during the day. Early morning OK before they're active. WILD BEES: forage at or BEFORE DAWN. Best practice for both: apply insecticides in EVENING OR NIGHT — protects all pollinators.

Insecticides vs Herbicides vs Fungicides — bee impact

Insecticides: generally TOXIC to bees; some more hazardous than others. Herbicides: unlikely to harm bees DIRECTLY. Fungicides: do not appear to affect adult bees but MAY AFFECT LARVAL development. Tank mixing insecticides + fungicides may be MORE TOXIC than either alone.

Granules vs Liquids — wildlife hazard

Granular/pelleted formulations: PARTICULAR CONCERN for birds + animals — mistaken for food or grit (used to grind food). Liquid formulations: SAFER when birds and other wildlife are in or near treated area. Place baits inaccessible to pets, birds, wildlife.

Endangered vs Threatened species

Endangered: on brink of extinction throughout all or significant part of range. Threatened: likely to become endangered. Both protected under federal Endangered Species Protection Program — county BULLETINS LIVE! identify required precautions (buffer strips, reduced rates, timing restrictions, possibly prohibition).

Air gap vs Backflow prevention device

Two methods to prevent BACK-SIPHONING. Air gap: physical separation between water hose discharge and tank surface; gap AT LEAST 2x diameter of discharge pipe. Backflow prevention device or check valve: mechanical device that stops reverse flow. Either method protects water source from contamination.

🌍 Pesticide Movement + Environmental Fate Quick Reference

Property / Process

What It Does

Key Specifics

Solubility

Ability of pesticide to dissolve in solvent (usually water).

HIGH water solubility = more likely to move with runoff or through soil. Highly soluble pesticides tend to leach.

Adsorption

Pesticide binds to soil particles. Attraction between chemical and soil.

Oil-soluble pesticides + positive-charged molecules bind tightly to clay + organic matter. Tightly adsorbed pesticides are LESS likely to move.

Persistence

Ability to remain present and active. Measured by HALF-LIFE.

Long half-life = more persistent. May provide long-term control but also produce illegal residues on rotational crops + harm nontarget organisms. Check label for replanting restrictions.

Volatility

Tendency to turn into gas or vapor.

INCREASES with temperature + wind. DECREASES with humidity (evaporation increases in drier conditions). Volatile pesticides cause vapor drift.

Chemical degradation

Pesticide breakdown by chemical reaction (often with water). NO living organisms involved.

Warm + wet conditions speed up; cool + dry slow it down.

Microbial action

Pesticide breakdown by soil microorganisms (fungi, bacteria).

Active in moist, warm soil with organic matter. Most important breakdown process for many soil-applied pesticides.

Photodegradation

Pesticide breakdown by sunlight.

Important for surface-applied pesticides. Some formulations include UV-protective coatings (e.g., microencapsulation) to slow photodegradation.

Spray drift

Off-target movement of small spray DROPLETS on air currents during liquid application.

Most common drift type. Control: larger droplets (low pressure + bigger nozzle orifice), wind 3-10 mph, boom 20-24 inches above target, downwind buffers, drift control additives. WIND speed/direction = most important factor.

Vapor drift

Pesticides as gaseous vapors moving from target area.

Volatile pesticides only — change to gas in heat. May volatilize HOURS after application. Many labels prohibit above 85 degrees F. Choose low-volatility products.

Particle / dust drift

Movement of solid particles (dust formulations or pesticide-bound soil) during or just after application.

Some pesticides remain active on soil particles long after application. Indoors: turn off fans, forced-air heating, A/C. Outdoors near buildings: close windows + vents.

Temperature inversion

Air at GROUND level COOLER than air above. Stable atmosphere; little vertical movement; mostly LATERAL air movement.

Drift more than 1 MILE possible. Develops EARLY EVENING, persists through night to MID-MORNING. Detection: smoke/dust HANGS in air; ground thermometer reads BELOW elevated thermometer. Drift may occur 1-3 hours after application.

Runoff

Surface movement of pesticides off treated site in water.

Greatest risk: heavy rains immediately after application; saturated or frozen ground. Travels via drainage systems, streams, ponds, surface water. Leave grass buffer strips next to streams/ponds.

Leaching

Downward movement of pesticide through soil to groundwater.

Worst profile: HIGH solubility + LOW adsorption + HIGH persistence + sandy soil + low organic matter + shallow water table + highly permeable geology. Macropores (cracks, worm holes, root channels) accelerate.

🛡️ Best Management Practices + Nontarget Protection Quick Reference

Practice / Concern

Rule

Key Specifics

Mixing/Loading distance

At least 50 FEET from wells, lakes, streams, rivers, storm drains.

Use sealed permanent or portable mixing/loading pad to prevent seepage. When possible, mix and load AT the application site.

Back-siphoning prevention

Maintain AIR GAP between water hose discharge end and tank surface — gap AT LEAST 2x diameter of discharge pipe. OR use backflow prevention device or check valve.

Back-siphoning starts with reduction in water pressure. Sucks tank contents directly into water source. Air gap prevents contamination of hose AND keeps pesticides from back-siphoning if pressure drops.

Wells

Do NOT store or mix pesticides around wells.

Poorly constructed, improperly capped, or abandoned wells allow direct entry of contaminated surface water into groundwater. Wells often located in/near treated fields.

Sinkholes + drainage

Never dispose of containers, dump, or rinse sprayers near sinkholes. Avoid contaminating drainage ditches.

NEVER clean tanks or discharge water from a tank into a street, along a road, or into a storm drain.

Granular cleanup

After granular applications, sweep or blow granules from sidewalks, driveways, patios onto the treatment area.

Granules on hard surfaces wash into storm drains during rain.

Sprayer cleanup

Clean sprayers at application site at safe distance from wells, ponds, streams, storm drains. Spray rinsate on treated area or label-permitted site, or use in next tank mix.

Do not exceed label rates. Check application equipment regularly for leaks/damage.

Sensitive areas — Outdoor

Schools, playgrounds, recreational areas, endangered species habitats, apiaries (honey bee sites), wildlife refuges, parks, livestock areas, ornamental plantings, sensitive food/feed crops.

Leave untreated buffer zone around sensitive area within larger target site. Check label for special restrictions.

Sensitive areas — Indoor

Hospitals, daycare centers, food processing/preparation/storage/serving areas, animal areas, ornamental plantings (in malls, buildings).

Pest management professionals only — well-trained applicators when sensitive area must be treated for regulated pest.

Bee protection

Apply insecticides EVENING or NIGHT. Do NOT apply when crops or weeds are in bloom. Avoid drift to attractive habitat or beehives. Choose least hazardous formulation/method.

Bees travel UP TO 3 MILES from hive. Notify beekeepers before applying bee-toxic products. Look for BEE HAZARD ICON in "Directions for Use." Tank mixing insecticides + fungicides may increase bee toxicity.

Bird protection

Liquid formulations safer near birds; granular/pelleted are PARTICULAR HAZARD (mistaken for food or grit).

Birds may: ingest granules/baits/treated seeds; be sprayed directly; eat treated crops; drink contaminated water; eat poisoned insects/prey. Place baits inaccessible to wildlife.

Secondary poisoning

Predators (birds, mammals) eating animals killed by pesticides.

Pesticide residues in dead animal bodies harm predators. Check label for secondary poisoning warnings. Past pesticides have been BANNED for fish/bird kills + reproductive failures.

Livestock contamination

Most contamination through feed, forage, drinking water — improper transport, storage, handling, application, or disposal.

Areas where domestic animals/livestock are kept = sensitive areas. Special precautions during nearby applications.

Endangered species

Federal Endangered Species Protection Program (state agencies + EPA). Pesticide products that might harm endangered species carry label statement directing applicators to county bulletins.

BULLETINS LIVE! (EPA Internet system) — county-specific. Required precautions: buffer strips, reduced application rates, timing restrictions, prohibition within identified habitat. ESA distinguishes ENDANGERED (brink of extinction) from THREATENED (likely to become endangered).

Phytotoxicity (plant injury)

Chemical injury to roots, stems, leaves, flowers, fruits.

Most phytotoxic injury due to herbicides. Damage from drift primarily, but also runoff and root uptake. Higher rates, wrong timing, unfavorable conditions all increase risk.

Required EPA outdoor label statement

"Do not apply directly to water, or to areas where surface water is present, or to intertidal areas below the mean high water mark. Do not contaminate water supplies when cleaning equipment or disposing of equipment wash waters."

Required on all pesticide products labeled for outdoor uses. Pesticides that could contaminate groundwater carry additional groundwater warning statements.

💡 Memory Hooks

Four properties: "Solubility, adsorption, persistence, volatility." How a pesticide behaves in the environment.

Three breakdown paths: "Chemical, microbial, sunlight." How pesticides degrade.

Three drift types: "Spray, vapor, particle." Three off-target air movements.

Wind window: "3 to 10 mph for spraying." Operational wind range — and watch for inversions when wind is low.

Mix-load buffer: "Fifty feet from wells and water." Critical separation distance for mixing/loading sites.

Back-siphoning rule: "Air gap two times the pipe diameter." Or use a check valve.

Groundwater significance: "Seventy percent of America's water." Why protection matters.

Bee range: "Bees fly three miles from the hive." Notification radius.

Pollinator timing: "Apply insecticides evening or night — bees forage by day." Best practice for both honey bees and wild bees.

Inversion identifier: "Cool below, warm above — smoke hangs in the air." Visual + thermometer detection.

Worst leaching profile: "Sand, low organic, shallow water, permeable geology." All four = highest leaching risk.

Bird hazard: "Granules look like food to birds." Liquids safer when wildlife present.

Volatility cutoff: "Above 85 degrees F = vapor drift risk." Common label limit.

Inversion timing: "Drift can move long distances 1-3 hours after application." Inversion's delayed-action danger.