Herbicides are compounds used to control unwanted plants, which compete with desirable vegetation for light, water, and nutrients. These products are broadly categorized as selective or non-selective. Selective herbicides target specific weed species, such as broadleaf weeds in a lawn, without harming surrounding turfgrass or other desirable plants. Non-selective herbicides, like those containing glyphosate, destroy nearly all plant matter they contact, making them suitable for areas where no vegetation is desired. Applying any herbicide correctly is necessary for effective weed control, protecting human health, and minimizing environmental impact.
Selecting the Right Herbicide and Pre-Application Checks
Effective weed management begins with accurately identifying the target weed, as this determines the most appropriate herbicide choice. Weeds are generally classified as broadleaf or grassy, and further categorized as annuals, which complete their life cycle in one season, or perennials, which return for multiple years. For instance, a broadleaf perennial weed like a dandelion may require a systemic post-emergent herbicide that moves through the plant to kill the deep taproot, while an annual grassy weed like crabgrass is best controlled with a pre-emergent product applied before the seeds germinate.
The product label serves as the instructions for the herbicide and must be read completely before any steps are taken. This document specifies the weeds controlled, the application rate, the required personal protective equipment, and any restricted entry intervals (REIs). Ignoring these instructions can lead to poor results, damage to desirable plants, or regulatory violations.
Before mixing or spraying, assess current and forecasted environmental conditions to ensure efficacy and safety. Applications should be avoided if rain is expected shortly after, as precipitation can wash the product off the foliage and into non-target areas or water sources. Wind speed requires careful monitoring, as winds higher than 10 miles per hour can cause spray droplets to drift significantly. The optimum wind speed for application is a light breeze between 3 and 10 miles per hour, which helps the spray reach the target without moving off-site.
Step-by-Step Application Techniques
The application process requires precise measurement and uniform coverage to ensure the correct dose reaches the target weeds. Most concentrated liquid herbicides are mixed with water based on the labeled rate, which is often given per unit of area or as a percentage solution. For example, a label may specify a certain number of fluid ounces of concentrate per 1,000 square feet, which must then be scaled to the total size of the area being treated.
Application is performed using equipment such as handheld, backpack, or hose-end sprayers, which must be calibrated to deliver the calculated amount of spray solution evenly over the target area. Calibration ensures the equipment dispenses the correct volume of liquid per unit of time or area, preventing both under-application and over-application. Proper technique involves maintaining a consistent walking speed and a stable nozzle height to achieve uniform coverage and an even pattern.
To minimize the risk of off-target movement, the nozzle should be kept as low as possible above the target. Using lower spray pressures and selecting nozzles that produce larger, coarser droplets will reduce the number of fine, drift-prone particles. Applicators should spray to achieve thorough coverage of the weed foliage, but not to the point of runoff, which wastes product and increases the risk of environmental contamination.
Safety Protocols and Post-Application Cleanup
Personal protection equipment (PPE) prevents the herbicide from contacting the skin, eyes, or respiratory system, and the specific items required are listed on the product label. At a minimum, this gear includes:
- Chemical-resistant gloves made of materials like nitrile or neoprene.
- Long-sleeved shirts.
- Long pants.
- Protective eyewear such as goggles or safety glasses.
Wearing these items minimizes exposure during the highest-risk activities, such as mixing and loading the herbicide concentrate.
Cleanup and decontamination procedures must be followed to secure the area and protect against residual chemical exposure. Empty herbicide containers must be triple-rinsed to remove residues before disposal. This process involves filling the container about 20–25% full with water, shaking it to rinse all interior surfaces, and then pouring the rinse water into the spray tank to be applied to the treated area.
After rinsing the containers, any leftover product must be stored in its original, labeled container in a secure location, away from children, pets, and food. The final step is personal hygiene, requiring the immediate removal of all contaminated clothing and showering with soap and water. Contaminated clothing should be washed separately from other laundry to prevent cross-contamination.