Beyond the smell: evaluation of wireworm potato varietal preference associated with tuber volatile emissions, palatability, and larval fitness

Wireworms (Agriotes sp.) represent a significant global threat in agriculture as soil-dwelling insect pests. Previous field observations have indicated varying susceptibilities of different potato varieties to wireworm attacks. In this laboratory study, we used three potato varieties known for displaying contrasted levels of susceptibility: Monalisa (high), Spunta (moderate) and Charlotte (low). We tested two groups of hypotheses: (1) wireworms display higher feeding activities when fed on a susceptible variety, which is also linked to faster larval development; (2) the most susceptible varieties are also the most attractive for wireworms, which can be explained by differences in their emissions of volatile organic compounds (VOCs), that guide larval foraging behaviour. Based on the results of our bioassays, we confirm our first hypothesis: wireworms feeding activity was higher on Monalisa tuber (i.e. longer galleries, lower weight gain of tubers), and these wireworms gained more weight and size than those that fed on the Charlotte variety, after 50 weeks of feeding. Based on our behavioural assays, we found that wireworms exhibit greater attraction towards Spunta tubers as opposed to those of Monalisa and Charlotte. The volatile collection analyses reveal a complex blend of 63 VOCs from potato tubers but do not suggest significant differences across the three varieties. The volatile profiles were however different between the two tuber phenological stages considered here. This study provides insights into the mechanisms of host detection and selection by wireworms.