Evaluation of Two Sampling Methods for Their Influence on the Population Statistics of Alfalfa Weevil (Coleoptera: Curculionidae) Larva Infestations in Alfalfa

Two sampling methods, systematic and simple random sampling, were evaluated for possible effects on the estimated population statistics of three variables for determining the degree of alfalfa weevil (AW), Hypera postica (Gyllenhal), larva infestations in alfalfa. We found no significant differences between the two sampling methods for estimated mean densities or variances of number of AW larvae, terminal buds that exhibited feeding, or length of alfalfa stems. Analyses concerning relative net cost and time required for collecting these samples indicated that the systematic method was the more desirable of the two. We also compared our estimates of AW larva densities and stem length with those of a second sampler, who used the single 3D-stemestimate recommended by Kentucky’s Integrated Pest Management Program. Results of these comparisons indicated that interperson variability as well as the number of samples used to estimate AW larva densities should be considered when designing integrated pest management sampling plans for AW. The only consistent source of bias we found was associated with the shake-bucket technique which was used to dislodge AW larvae from alfalfa stems. We found that the shake-buck technique consistently underestimated the number of AW larvae present in the samples.