Illinois Field Crop Applicators Practice Test

What is the economic threshold for the first cutting of alfalfa weevil larvae?

1. 1 or more larvae per stem

2. 3 or more larvae per stem and 20% of the tips skeletonized

3. 5 or more larvae per stem

4. 0.5 or more larvae per stem

The correct answer is: 3 or more larvae per stem and 20% of the tips skeletonized

In the context of managing alfalfa weevil populations, the economic threshold is a critical concept that helps determine when to take action against these pests to prevent significant economic loss. The correct answer reflects the point at which damage becomes economically concerning, which is defined as having three or more larvae per stem coupled with 20% of the plant tips being skeletonized. This threshold is important because alfalfa weevils can cause serious damage to crops if their populations rise too high. By setting the threshold at this specific level, it allows for a balance between the cost of pest management measures and the potential yield loss that could occur if management is delayed. Action taken when these criteria are met ensures that the management strategy is both effective and economically viable. In contrast, lower thresholds may not account for the actual extent of damage that becomes economically significant, leading to unnecessary pesticide applications, while higher thresholds may result in excessive crop damage and financial loss.