When applying postemergence herbicides, which weather condition should be avoided?

When applying postemergence herbicides, which weather condition should be avoided?

• A. Hot, dry weather
• B. Warm, moist conditions
• C. Cool, overcast days
• D. Overcast rainy days

Answer: (A)

When applying postemergence herbicides, conditions that stress the plant and the spray droplet can undermine both efficacy and safety. In hot, dry weather, turf leaves tend to close their stomata to conserve water, which slows or blocks the herbicide from entering the leaf tissue. The high heat also causes spray droplets to evaporate or evaporate too quickly, leading to uneven coverage and reduced uptake. The combination of stressed, less-tolerant plants and poor spray performance often results in weaker control or even turf injury. For these reasons, avoid applying under hot, dry conditions and instead choose cooler, more humid times with adequate leaf moisture to maximize absorption and effectiveness.

When applying postemergence herbicides, conditions that stress the plant and the spray droplet can undermine both efficacy and safety. In hot, dry weather, turf leaves tend to close their stomata to conserve water, which slows or blocks the herbicide from entering the leaf tissue. The high heat also causes spray droplets to evaporate or evaporate too quickly, leading to uneven coverage and reduced uptake. The combination of stressed, less-tolerant plants and poor spray performance often results in weaker control or even turf injury. For these reasons, avoid applying under hot, dry conditions and instead choose cooler, more humid times with adequate leaf moisture to maximize absorption and effectiveness.