The effects of wireworm Limonius agonus feeding on buckwheat roots
Citation
Krolikowski, S., Y. Bohorquez, J. Renaud, T. McDowell, I.M. Scott. 2018. The effects of wireworm Limonius agonus feeding on buckwheat roots. Poster presentation at the Ontario Pest Management Conference, November 6, 2018, Guelph, ON.
Résumé en langage clair
The focus of the presentation was to provide evidence for the interaction between buckwheat plants and a soil insect, the wireworm. We completed this research in order to better understand how the feeding by the insect induces root defenses that may be responsible for wireworm mortality. A two season microplot trial determined that wireworm survival was reduced after feeding on buckwheat roots for a period of 3 to 6 weeks. Most wireworm remained in the top soil layer which suggests that compounds released from the roots over the 6 week period did not deter or repel wireworm from the buckwheat rhizosphere. Feeding on the buckwheat did not reduce root weight or length, or affect wireworm weight, however, certain metabolites increased in concentration only in the roots after wireworm feeding. These interesting findings support the theory that an induced response by buckwheat to wireworm leads to a negative effect on the insects when the roots are further consumed. This should encourage other researchers to study the interaction between buckwheat and wireworm.
Résumé
Buckwheat (Fagopyrum esculentum) roots possess chemicals that have allelopathic properties that supress weeds and certain soil dwelling insects. Planting buckwheat as a rotation crop before potatoes significantly reduces damage and increases marketable yield in wireworm-infested fields. Preliminary chemical characterization of buckwheat has indicated it possesses a complex array of phytochemical components, the majority of which remain unidentified. In order to determine which phytochemicals produced by the roots are associated with the anti-insect activity, field experiments were conducted for two consecutive years (2016-17). Half of the microplot tiles planted with buckwheat or barley (Hordeum vulgare) were infested with wireworms (Limonius agonus) three weeks after seeding. Soil and plants were sampled at 3, 6 and 9 weeks, while wireworm were sampled at 4.5 (2017 only), 6 and 9 weeks. In buckwheat tiles wireworm survival was lower after 6 or 9 weeks compared to barley. Most of the wireworm collected from all treatment tiles remained in the top two soil depths (0-10 cm and 10-20 cm) regardless of plant type. The roots were longer and weighed more within tiles infested by wireworm suggesting a plant growth over-compensation due to herbivory since the weight gain of surviving wireworm was no different between plant types. A metabolomic analysis approach determined chemical differences between plant types and growing periods. A comparison of compounds in the roots from both infested and un-infested tiles indicate induced chemical levels as well as different compounds present after herbivory which may explain the differences in wireworm survival.