Which item on the list concerns the toxicity threshold used to gauge the pesticide's effect on pests?

• 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: (B)

The key idea is how the strength of a pesticide against pests is measured. LD50 is the standard toxicity threshold used to gauge a pesticide’s effect on pests. It represents the dose required to kill 50% of a test pest population under defined conditions. A low LD50 means the substance is highly toxic to pests, so saying the LD50 is too low directly points to the pesticide’s potency against pests.

The other statements don’t describe a toxicity threshold: pests developing resistance means they survive exposure due to genetics or adaptation, not a measured threshold of toxicity. Applying the product at too high a rate concerns exposure or usage rather than the intrinsic toxicity to pests. Missing a restricted-entry interval relates to human safety and handling rules, not the pesticide’s effect on pests.