Seasonality of Colaspis crinicornis (Coleoptera: Chrysomelidae) and its Injury Potential to Corn in Southeastern Nebraska.

Colaspis crinicornis Schaeffer (Coleoptera: Chrysomelidae) primarily occurs in the Great Plains, United States. Although C. crinicornis has historically been considered a non-pest and is rarely found in agricultural systems, population densities of this species have been increasing in corn, Zea mays L., and soybean, Glycine max (L.) Merrill, over the last decade in southeastern Nebraska. As part of a comprehensive project to understand the life history and pest potential of C. crinicornis, a field study was conducted to: understand adult seasonality of C. crinicornis using emergence cages and whole-plant-count sampling in cornfields and sweep-net sampling in soybean fields; confirm voltinism and the overwintering stage; and evaluate the potential of larvae to cause economic injury to corn roots. Data indicate that C. crinicornis is univoltine in southeastern Nebraska and overwinters as medium-large larvae at least 20 cm deep in the soil. Adults were present from June through August with peak emergence in July. The C. crinicornis lifecycle is similar to related Colaspis species. Root injury to corn was minor at population densities encountered in the field, and therefore, C. crinicornis is unlikely to cause economic loss. C. crinicornis may be an example of an insect species that has exploited open niches in crops that have been created by changes in agricultural and pest management practices. The lifecycle and polyphagous nature of the insect, annual crop rotation, the shift to minimum tillage, and replacement of insecticides with Bacillus thuringiensis Berliner (Bt) traits may have collectively facilitated establishment and increased survival in agroecosystems.