Wireworm feeding behaviours: the capacity of Hypnoidus bicolor to damage soybean under different environmental conditions

Important agricultural pests in the Canadian Prairies, wireworms are the soil-living larvae of click beetles. Several notable species are found within the Prairies, with Hypnoidus bicolor being the most ubiquitous in most parts of the region. Despite their prevalence, H. bicolor is often disregarded as a significant pest species due to their comparatively small larval sizes. However, few studies have directly assessed the capacity of wireworms to cause damage to particular crop(s), and thus far no such studies have been undertaken for H. bicolor. We therefore carried out laboratory experiments under controlled environmental conditions, with soil and wireworms transplanted from the field, to determine the capability of H. bicolor to damage soybean. As expected, wireworm damage was strongly associated with larval densities, with more severe soybean injury occurring in the presence of greater numbers of H. bicolor. Further, feeding damage to soybean by H. bicolor was greater at lower temperatures (10 degrees C and 20 degrees C) than at higher temperatures (30 degrees C). In terms of soil texture, soybean grown in loam and silt soils were the most susceptible to wireworm damage and those grown in clay soil were the least affected. Although the larvae are not capable of damaging soybean to the same extent as other Prairie pest species, Limonius californicus and Hypnoidus abbreviatus, in high enough densities and under ideal environmental conditions H. bicolor can significantly impact soybean growth. Overall, our study suggests that soybean is susceptible to considerable wireworm damage and H. bicolor is an under recognized pest species of this legume.