Weed Killer Safety Guide: Labels, PPE, Spraying and Storage

It means the label's directions are legally binding, not suggestions. You may use less product or treat fewer sites than the label allows, but not more product, more often, on sites it does not list, or in ways it prohibits. Read the whole label before buying, again before mixing, and keep it with the product. The key sections:

• Product name and active ingredients: the chemicals that do the work, by percentage. Compare active ingredients, not brand names.
• EPA registration number: proof the product is registered for the uses listed.
• Signal word: CAUTION, WARNING or DANGER, describing short-term toxicity.
• Precautionary statements: hazards to humans and domestic animals, required protective equipment, and environmental hazards such as toxicity to fish, bees or groundwater.
• First aid: what to do for eye, skin, inhalation or swallowing exposure.
• Directions for use: the sites (lawn types, beds, driveways), target weeds, rates, timing, weather limits, rainfast time, re-entry and replanting intervals.
• Storage and disposal: how to keep the product and handle leftovers and empty containers.

Pay particular attention to lawn grass restrictions. For example, Ortho WeedClear Weed Killer for Lawns Concentrate, 1 gal lists over 250 weeds on most turf but excludes Floratam St. Augustine, and Scotts Turf Builder Weed and Feed5, 33.95 lb excludes St. Augustine and several other grasses.

Signal words come from EPA toxicity categories based on the product as sold, and they describe acute (short-term) hazards such as eye, skin, swallowing and breathing effects.

Wear at least what the label lists under precautionary statements; that is the legal minimum. For most homeowner herbicides it looks like this:

• Long-sleeved shirt, long pants, socks and closed shoes. No sandals, shorts or bare arms.
• Chemical-resistant gloves such as nitrile chemical-resistant gloves. Cloth and leather gloves absorb chemicals and hold them against skin.
• Eye protection: safety glasses such as NoCry Clear Anti-Fog Safety Glasses at minimum, or chemical splash goggles when the label calls for goggles or when pouring concentrates, which are the riskiest step.
• A respirator only if the label requires one, of the type it specifies.

Afterward, wash gloves before removing them, wash hands before eating, drinking, smoking or using the bathroom, and launder spray clothes separately from family laundry. Discard clothing soaked with concentrate as the label directs.

A selective herbicide kills certain plants and spares others when used as labeled. Broadleaf lawn weed killers target dandelion, clover and plantain while leaving grass: examples include Southern Ag Amine 2,4-D Weed Killer, 32 oz (active ingredient 2,4-D amine), Spectracide Large Plot Weed Stop for Lawns Concentrate, 1 gal and Ortho WeedClear Weed Killer for Lawns Concentrate, 1 gal. Other selective products target grassy weeds or sedges in turf, such as BASF Drive XLR8 Crabgrass Killer Concentrate, 64 oz (quinclorac) for crabgrass. Selective does not mean safe for every plant: many broadleaf herbicides injure vegetables, flowers, shrubs and young trees they touch or drift onto.

A non-selective herbicide kills or damages any green plant it contacts, grass included. Roundup Weed and Grass Killer4 Concentrate, 1 gal is for bed edges, fence lines and full lawn renovation, and its label sets replanting intervals. RM43 Glyphosate Plus Weed Preventer Total Vegetation Control, 2.5 gal (glyphosate 43 percent plus a weed preventer) is a bare-ground product for gravel, fence rows and driveways only, never lawns or beds, because it prevents growth for up to a year. Non-selective products call for spot spraying with a shield or careful aim, and extra care near roots of trees and shrubs.

A pre-emergent stops weed seeds from establishing and does nothing to weeds already growing; a post-emergent kills weeds that have already come up. Active ingredients are listed below only where the product listing states them; check each label for the rest.

Pouring and measuring concentrate is the highest-exposure step, so slow down:

• Read the rate on the label for your target weed and site, usually ounces per gallon of water or per 1,000 square feet.
• Mix outdoors in a ventilated spot on the lawn or a hard surface away from storm drains, wells, ponds and play areas, with kids and pets inside.
• Use dedicated measuring tools marked for pesticide use only, never kitchen cups or spoons, and never measure by eye.
• Fill the sprayer about halfway with water, add the measured product, then add the rest of the water and agitate, unless the label gives a different order.
• Mix only what you will use that day. Many labels say not to store diluted spray.
• Never combine products unless the label specifically allows that tank mix. Some combinations react, damage turf or create hazards.
• Some labels require additives: Syngenta Tenacity Turf Herbicide, 8 oz calls for a nonionic surfactant for post-emergent use, and treated weeds turn white before dying, as its label describes.
• Keep a dedicated herbicide sprayer. Residue left in a sprayer can injure plants later, so do not use the same tank for plant-safe sprays.

Labels written per 1,000 square feet only work if you know how much water your sprayer puts on that area at your walking pace. Calibration takes 15 minutes with plain water:

• Mark a test area of 1,000 square feet, such as 20 by 50 feet, on the lawn.
• Fill the sprayer with a measured amount of water and pump or set it to the pressure you will use.
• Spray the area evenly at a normal, steady walking pace with slight overlap, as if applying product.
• Measure what is left. The water used is your output in gallons per 1,000 square feet.
• Do the math: tank gallons divided by gallons per 1,000 square feet equals the area one tank covers. Multiply the label rate per 1,000 square feet by that area (in thousands) to get product per tank.

For example, with made-up numbers rather than any label's rate: if a 2 gallon tank sprays 0.5 gallon per 1,000 square feet, one tank covers 4,000 square feet, so a product labeled at 1 ounce per 1,000 square feet needs 4 ounces in the tank. Extension services also teach a shortcut: spray a square about 18.5 by 18.5 feet (roughly 1/128 of an acre), and the fluid ounces used equal gallons per acre.

Consistent pressure keeps calibration valid. Hand pump sprayers lose pressure as they empty, so pump back up often; battery sprayers with regulators, like the My4Sons M4 Battery Powered Backpack Sprayer, 4.5 Gallon, hold a set pressure. Use a flat fan nozzle for even broadcast coverage and a cone or adjustable nozzle for spot treatments.

Weather causes most homeowner herbicide problems, and many labels set specific limits. General rules:

• Wind: do not spray in gusty or strong wind, and follow the label's wind limit; many product labels caution against spraying when wind exceeds about 10 mph. A light, steady breeze blowing away from gardens, trees and neighbors is best.
• Dead calm: also a risk. Still, cool early mornings and evenings, especially with fog, can mean a temperature inversion that carries fine droplets and vapor long distances.
• Rain: check the rainfast time, how long the product needs before rain or irrigation. Listings vary: Spectracide Large Plot Weed Stop for Lawns Concentrate, 1 gal is rainproof after 6 hours, Roundup Weed and Grass Killer4 Concentrate, 1 gal in about 30 minutes, and BASF Drive XLR8 Crabgrass Killer Concentrate, 64 oz in under an hour. Do not spray before forecast heavy rain, which washes product off target and into waterways.
• Temperature: many labels warn against applying in high heat, which stresses turf and can increase vapor movement for some active ingredients, and weeds under drought stress absorb less. Follow any temperature range on the label.
• Pre-emergents often need watering in after application; the label says how much and how soon.

Drift is spray moving off target as droplets or vapor. It kills garden plants, injures trees and harms neighbors' yards.

• Use lower pressure and coarse droplets. High pressure makes fine mist that floats. Choose a coarse spray setting or low-drift nozzles.
• Keep the nozzle close to the target, a few inches above weeds rather than waving the wand high.
• Spot spray individual weeds instead of broadcasting a whole lawn with a few weeds.
• Shield sprays near desirable plants with a piece of cardboard or a spray shield, and never spray non-selective products on a windy day near beds.
• Respect buffers around vegetable gardens, ornamentals, trees, ponds and property lines, including any distances on the label.

Pollinators: bees forage on flowering lawn weeds like clover and dandelion. Read the environmental hazards section for bee warnings, avoid spraying weeds in bloom while bees are active, and mow flowers off first or spray in the evening when fewer bees are foraging, if the label allows. Never spray blooming trees, shrubs or garden flowers.

Waterways: keep herbicides out of storm drains, gutters, ditches, ponds, streams and wells.

• Never spray or spread onto driveways and sidewalks where runoff reaches the street; sweep stray granules back onto the lawn.
• Mix and rinse equipment on the lawn, away from drains and wells, never at a sink or storm drain.
• Leave untreated buffers along ponds and streams as the label directs.
• Do not apply before heavy rain, or to frozen, saturated or sloped bare soil where runoff is likely.

• Keep children and pets indoors while mixing and spraying, and move toys, pet bowls and furniture off the area first.
• Keep people and pets off treated areas until the spray has dried, or longer if the label says. Granular products often need watering in and drying before re-entry; follow the label.
• Never leave products or mixed sprayers unattended, even briefly.
• Never put herbicide in food or drink containers. Accidental poisonings often involve products transferred to a bottle.
• Know the numbers: Poison Control at 1-800-222-1222 for people, and the ASPCA Animal Poison Control Center at (888) 426-4435 for pets (a fee may apply). Have the product label in hand when you call.

Storage: keep herbicides in their original containers with labels attached, tightly closed, in a locked cabinet or high locked shelf out of reach of children and pets. Store them away from food, pet food, seed and fertilizer, in a dry place protected from freezing and extreme heat if the label says so. A garage or shed cabinet with a lock works well. Buy only what you will use in a season or two.

Disposal: the best way to dispose of extra product is to use it up as labeled. Never pour herbicide down a sink, toilet, storm drain or onto the ground. Take leftover products to a household hazardous waste collection program. Rinse empty liquid containers as the label directs, adding the rinse water to the sprayer, and never reuse pesticide containers for anything.