However, scouting can be discontinued whenever the beetle population reaches or exceeds the threshold level and therefore categorizes that field with the potential for economic damage the following year. If this occurs, apply a soil insecticide the next year or rotate to a different crop. If beetles are not found the first few times a cornfield is scouted, continue weekly field checks until late August for beetles that may move in from surrounding cornfields. Various factors affect the accuracy of beetle counts. Competence and diligence when making beetle counts are essential.
Sample size is also important.
In general, as the number of sample sites increases, so does the accuracy of the estimate of the beetle population. The larger the field, the more sample sites are needed to accurately estimate the beetle population density. Conversely, the smaller the field, the fewer the sample sites needed. We suggest a minimum of five sample sites per field, regardless of field size, or approximately one sample site per 25 acres for cornfields exceeding 130 acres. If beetle populations appear to be approaching the threshold level, increase the number of sites to provide a more accurate estimate.