If increasing the application rate does not improve control, which listed factor could be responsible?

If increasing the application rate does not improve control, which listed factor could be responsible?

• A. The pest developed resistance to the pesticide
• B. The LD50 of the pesticide is too low
• C. The rate of product applied was too high
• D. The restricted-entry interval was not followed

Answer: (C)

When a higher application rate doesn’t improve control, the problem is usually with how the product is deposited and used, not with the pest. If the rate is pushed too high, droplets can coalesce, run off leaves, or form a thick film that actually reduces effective contact with the pest. This means you’re not achieving better exposure or uptake, so more chemical doesn’t translate to more control. In other words, there’s an optimal rate for the product, and over-applying can waste product and even hinder performance. This isn’t best explained by pest resistance, which would typically show reduced susceptibility across doses rather than a flat lack of improvement with higher rates. The LD50 being too low would imply high potency at lower doses, not a failure to gain extra control with more product. Skipping the restricted-entry interval affects worker safety and crop handling, not the pest’s response to the dose.

When a higher application rate doesn’t improve control, the problem is usually with how the product is deposited and used, not with the pest. If the rate is pushed too high, droplets can coalesce, run off leaves, or form a thick film that actually reduces effective contact with the pest. This means you’re not achieving better exposure or uptake, so more chemical doesn’t translate to more control. In other words, there’s an optimal rate for the product, and over-applying can waste product and even hinder performance.

This isn’t best explained by pest resistance, which would typically show reduced susceptibility across doses rather than a flat lack of improvement with higher rates. The LD50 being too low would imply high potency at lower doses, not a failure to gain extra control with more product. Skipping the restricted-entry interval affects worker safety and crop handling, not the pest’s response to the dose.