Illinois Field Crop Applicators Practice Test

What leads to higher herbicide activity in conditions?

1. High relative humidity

2. Cool temperatures

3. Poor soil moisture

4. Fast evaporation

The correct answer is: High relative humidity

High relative humidity contributes to improved herbicide activity because it enhances the retention of the herbicide on plant surfaces and reduces evaporation rates. When humidity levels are elevated, the moisture in the air slows down the rate at which droplets of the herbicide dry on the leaves, allowing for a longer contact time with the target plants. This extended interaction increases the likelihood of effective absorption by the plant, leading to a more significant herbicidal effect. In contrast, cool temperatures can slow down the metabolic processes within plants, potentially reducing their uptake of the herbicide. Poor soil moisture often leads to stress in plants, which can also interfere with the effectiveness of herbicides as uptake mechanisms may be hindered under drought conditions. Fast evaporation, particularly under low humidity or high temperature conditions, can result in decreased herbicide concentration on the target area, significantly reducing its effectiveness. Therefore, high relative humidity plays a crucial role in maximizing herbicide activity.