Evaluating Single Treatment Data Using Abbott’s Formula With Reference to Insecticides

Abbott’s formula is often applied to entomological field data to distinguish the effects of pesticide treatment from those caused by natural factors. Although one would normally hope to use inferential statistics in applying Abbott’s formula, logistical and economic constraints sometimes preclude the necessary experimental replication. We show that the use of Abbott’s formula in experiments involving a single treatment and a single check plot usually produces a biased estimate of the population reduction due to treatment. The reasons for this bias are presented as guidance in the design of pesticide trials and in the interpretation of their results.