A COMPARISON OF 3 METHODS OF MONITORING THE CARROT WEEVIL, LISTRONOTUS-OREGONENSIS (LECONTE) (COLEOPTERA, CURCULIONIDAE)

The carrot weevil, Listronotus oregonensis (LeConte), was monitored at 11 research or commercial carrot plantings at Holland Marsh, Kettleby , Ontario, using three methods, i.e. wooden plate (Boivin) traps to ca pture adults, carrot root sections placed in the soil to detect ovipos ition, and recording the numbers of adults present on carrot root sect ions. All three methods provided similar records of the seasonal patte rn of adult activity. At most sites, thresholds used to determine the need for insecticide applications were reached or exceeded soon after the beginning of monitoring. There were significant linear relationshi ps among the seasonal activity parameters generated by the three metho ds and between those parameters and percentage injury at harvest. Cont rol programs that would have resulted from the use of each method are discussed.