Glyphosate is a widely used, non-selective herbicide designed to control a broad spectrum of grasses and broadleaf weeds. As a systemic chemical, it is absorbed through the foliage and moves throughout the plant, including the roots, to achieve complete control. Effective use requires a precise approach to preparation, application, and timing. This method ensures the chemical reaches its target without waste or harm to desirable vegetation.
Preparing the Solution and Understanding Dilution
Achieving the correct concentration is the initial step toward maximizing glyphosate efficacy, as product concentrations vary widely. The product label must be consulted to determine the correct dilution rate, often expressed as fluid ounces of concentrate per gallon of water. A 41% formula will require a different mixing ratio than a 53.8% formula to deliver the same amount of active ingredient. A common rate for 41% glyphosate is two to four fluid ounces per gallon of water for spot treatment.
Mixing procedures begin by filling the spray tank approximately half full with water to facilitate agitation. If the water is “hard,” adding ammonium sulfate (AMS) before the concentrate can improve performance by preventing hard water ions from binding to the herbicide molecule. Next, add the measured concentrate, followed by any required adjuvants like a non-ionic surfactant (NIS). Surfactants reduce water surface tension, allowing spray droplets to spread and penetrate the leaf surface better, though many commercial formulations already include a surfactant.
The tank should then be filled to the final volume with water while maintaining gentle agitation to ensure a homogenous solution. Improper dilution, either too weak or too strong, is the most common reason for application failure. Precise measurement is necessary before the application begins.
Choosing the Right Application Technique
The application method should be selected based on the size of the area and the proximity of desirable plants. Broadcast spraying is used for large areas, requiring an even, consistent spray pattern. Spot treatment involves directing the spray onto individual weeds or small patches, often using a handheld or backpack sprayer. Apply the solution until the foliage is thoroughly wet, but without reaching the point of runoff, which wastes product and increases contamination risk.
Specialized techniques, like a wick or roller applicator, are useful for selectively treating weeds taller than desirable plants. These applicators wipe the solution directly onto the weed’s foliage, minimizing contact with other vegetation. For broadcast applications, the sprayer must be calibrated to deliver a consistent volume per area. This involves ensuring even coverage and maintaining a constant ground speed and spray pressure on the green, actively growing leaf tissue.
Maximizing Efficacy Through Proper Timing
The systemic action of glyphosate makes timing a major factor in its success. The herbicide is most effective when applied to actively growing weeds, which favors rapid absorption and translocation to the root system. Applying to weeds stressed by drought, heat, or frost can reduce efficacy because the plant’s metabolism slows down, hindering chemical movement.
Optimal application occurs when temperatures are in the 60°F to 75°F range, as plant growth is vigorous. The timing must also account for environmental factors, particularly wind, to prevent drift onto non-target plants. Wind speeds should be low, less than 10 miles per hour, and the spray nozzle should be kept as low as practical to the target foliage.
A key consideration is the “rain-fast” period, the minimum time required between application and rainfall for absorption. While many modern formulations are rain-fast in one hour, a six-hour rain-free forecast is a reliable guideline to ensure adequate absorption. Applying during the morning often provides the best results because weeds have a longer period of light and active growth after treatment, enhancing herbicide movement.
Essential Safety Measures and Post-Use Cleanup
Personal protection equipment (PPE) is mandatory when handling any concentrated herbicide to minimize exposure risks. The product label specifies the exact PPE requirements, which must be strictly followed to protect the skin and eyes from accidental contact. At a minimum, applicators should wear:
- Long-sleeved shirts
- Long pants
- Chemical-resistant gloves
- Protective eyewear
Washing the outside of the gloves before removal is necessary to avoid contaminating the hands.
Preventing environmental contamination is necessary during and after application. Applicators must prevent spray drift by monitoring wind conditions and using appropriate spray pressure and nozzle types. Care must be taken to avoid spraying near water sources or desirable plants that could be damaged by accidental contact.
Once the application is complete, proper equipment cleanup and container disposal are required. The spray tank and all associated equipment should be triple-rinsed with water immediately after use. This involves partially filling the tank with clean water, agitating it, and then spraying the rinse water onto an already treated area. Empty concentrate containers must also be triple-rinsed before disposal, following all local regulations.