The best potato: evaluation of wireworms varietal preference

Wireworms are among the most important soil-dwelling insect pests worldwide. Like above-ground phytophagous species, wireworms use Volatile Organic Compounds (VOCs) produced by underground plant organs to locate adequate hosts. In this study, we tested the hypothesis that VOCs are involved in wireworm host finding behavior and allowed them to discriminate between suitable and unsuitable hosts. We first identified the VOCs emitted by potato tubers from three potato cultivars, at two phenological stages. These cultivars were selected based on levels of infestations in the field: Monalisa (susceptible), Spunta (intermediate) and Charlotte (less sensitive). Using a non-destructive headspace dynamic sampling and gas chromatography-mass spectrometry, we were able to identify a complex blend of 65 VOCs released in the rhizosphere. Interestingly, we observed significant differences in VOCs composition between the two phenological stages but not between cultivars. Then we observed wireworms foraging behavior in dual-choice olfactometers, and found out that wireworms were more attracted to “Spunta” tubers compared to “Monalisa” and “Charlotte” cultivars, while there were no differences between the latter two. The weight variations of wireworms and tubers over 15 days were not significantly different among the three cultivars. However, wireworms made significantly more and larger galleries inside the “Monalisa” tubers compared to the two others. This study revealed that the most susceptible cultivar in the field is not the most attractive for wireworms but the one that initiates more foraging activity. Moreover, the chemical analysis suggests that VOCs can be used to select a phenological stage, while other cues may be implicated to identify cultivars. This study brings new insights into the wireworm-potato interactions, especially on the mechanism of host detection, which can be valuable to develop new sustainable alternatives in integrative pest management.