Multi-way methods for wireworms’ control: volatile organic compounds, potato varietal preferences and entomopathogenic fungi

Wireworms are a major threat to agriculture worldwide. These soil-dwelling insect pests cause major economic losses. Following the recent ban on neonicotinoids, it has become crucial to develop integrated management strategies targeting this insect. In this study, we sought to (i) assess the feeding preferences of wireworm larvae for different potato varieties and (ii) identify new strains of effective entomopathogenic fungi. We selected three potato varieties that exhibit varying levels of susceptibility to wireworm damage in the field: Monalisa (high damage), Spunta (moderate damage), and Charlotte (low damage). In one-choice bioassays, we observed that wireworms displayed higher feeding activity on Monalisa tubers compared to the other varieties. Additionally, after 50 weeks, we found that wireworms experienced an accelerated life cycle on Monalisa compared to Charlotte. Since wireworms rely on volatile organic compounds (VOCs) to locate hosts, we hypothesized that Monalisa's susceptibility might be linked to specific VOC emissions. However, dual-choice bioassays revealed an unexpected pattern: while Monalisa sustained the highest damage, Spunta showed greater attraction. Using non-destructive headspace dynamic sampling and gas chromatography, we identified a blend of 63 VOCs released by tubers in the rhizosphere. No significant differences in VOCs composition were found across varieties. These findings suggest that the variety most susceptible to damages is not the most attractive but rather the one that promotes higher wireworm foraging activity, implicating other olfactory cues (such as CO₂ and secondary metabolites) in host selection. In a further step, we tested the biocidal activity of 11 strains of entomopathogenic fungi on wireworms, and after 12 weeks of continuous exposure, two new strains significantly reduced wireworm survival. Encapsulating these two strains in a biodegradable matrix optimized for field application showed that one strain was particularly effective in killing wireworms. Collectively, these findings contribute valuable insights toward integrated management strategies for wireworm control.