What must occur for control methods to be justified according to the guidelines?

Justification for control methods often hinges on the relationship between economic thresholds (ET) and economic injury levels (ETL). The economic threshold is the pest population density at which control measures need to be initiated to prevent the pest population from reaching the economic injury level. The economic injury level is the pest density at which the cost of damage exceeds the cost of control measures.

When the economic threshold is lower than the injury level, it indicates that the pest population is manageable without incurring significant economic loss, thus control measures are not justified. However, once the pest population exceeds the economic threshold, it suggests that control measures are warranted to prevent further economic damage. Therefore, for control measures to be justified, the economic threshold must be lower than the economic injury level, signifying a need for intervention to mitigate potential losses.

This relationship is fundamental for making sound pest management decisions, ensuring that resources are utilized efficiently and economically. Thus, the correct understanding of this threshold relationship is crucial for herbicide applicators and others involved in pest management to carry out effective control strategies.