Phenological and Monitoring Considerations for Carrot Weevil (Listronotus oregonensis) in Nova Scotia

Abstract

Carrot weevil, Listronotus oregonensis, is a pest of carrot throughout Eastern Canada. Oviposition and development of carrot weevil were monitored in Nova Scotia and the degree day (DD) timing of development of key life history events was compared with that previously determined for a carrot weevil population in Quebec. Oviposition occurred earlier, and lasted slightly longer in Nova Scotia than Quebec. On carrot plants, oviposition commenced at the 4 true-leaf stage with 70% of eggs laid between the 4-8 true-leaf stages. An interaction study between click beetles, Agriotes spp., and carrot weevil adults confirmed that the Boivin trap is efficient in monitoring carrot weevil even when the trap is occupied by up to 90 click beetles. A comparison of damage caused by carrot weevil larvae and wireworms showed that carrot weevil larvae make a continuous furrow while wireworm damage is more variable, ranging from a small entry hole to an irregular excavation. Mean incidence of feeding damage for both carrot weevil larvae and wireworm occurred on the top third of the carrot.