Economic Threshold is defined as the pest density at which control measures should begin.

• A. The maximum pest density allowed in a field
• B. The minimum pesticide dose needed
• C. The pest density at which control measures should begin
• D. The economic return of the crop

Answer: (C)

The key idea being tested is when to act to control pests based on economic considerations. An economic threshold is the pest density at which you should start control measures so that the expected cost of the pest damage from allowing the population to continue does not exceed the cost of taking action. In other words, it’s a trigger point set below the level where damage would become economically unacceptable, giving you time to apply treatment before losses escalate.

Think of it as a balance: if pests are present at a level where their potential damage would equal what you’d spend on control, it makes sense to treat. If you wait until damage would be worse than the cost of control (the economic injury level), you’ve missed the optimal window. This is why the correct description is the pest density at which control measures should begin.

The other ideas don’t fit. It’s not about the maximum pest density allowed, nor about the minimum pesticide dose needed, nor about the crop’s economic return itself; the threshold is specifically about the pest population level that signals when action should start to prevent economic loss.