Ecology and management of wireworms (Coleoptera: Elateridae) in conventional and organic production systems

Wireworms are the subterranean larval stage of click beetles (Coleoptera: Elateridae), generalist herbivores that feed on a wide range of crops and cause serious damage. Wireworm management is challenging due to their long life cycle, subterranean habitat, wide range of host plants, and lack of effective chemical approach in most crops. Thus, developing an effective alternative control approach is an urgent need. The overall aim of this research study was to evaluate alternative [to insecticides] tactics that could be used as components of effective IPM strategies against wireworms. In Chapter 1 we provide an overview of wireworm's biology and management practices. In Chapter 2 we focused on biological control to evaluate the efficacy of entomopathogenic nematodes and fungi as single and mixed application against Limonius californicus and L. infuscatus in organic vegetable farms. The results showed the higher efficacy of commercial EPN, Steinernema feltiae, against Limonius species than entomopathogenic fungi. In Chapter 3, we focused on cultural control as a component of integrated pest management for wireworm control. We evaluated the efficacy of brown and yellow mustard and their byproducts, including defatted seed meal and seed meal concentrated extract against Limonius spp. Our finding indicated the effectiveness of brown mustard concentrated extract on reducing the wireworm population. However, it has a negative impact on the field-residing entomopathogenic nematodes. In Chapter 4, in the component of cultural control, we evaluated the wireworm, L. californicus, preference to three different crops, pea, bean, and wheat, for identifying an effective trap crop. We also quantified CO2 and organic volatile compounds released from each plant's root and evaluated the wireworm response toward the synthetic volatiles. Detailed results are provided in chapter 4. Finally, we looked at the novel new technology of RNA interference to find the effective target genes in wireworms for application as bioinsecticides and/or transgenic plants to control wireworms. In the concluding chapter, Chapter 6, we summarized our findings on the efficacy of different management tactics, biological, cultural, and molecular, to control Limonius species in cereals and organic production systems.