Degree-day models to predict carrot weevil (Coleoptera: Curculionidae) emergence and oviposition in Nova Scotia, Canada
Citation
Blatt, S., Joseph, D.A., Cutler, G.C., Olson, A.R., White, S. (2020). Degree-day models to predict carrot weevil (Coleoptera: Curculionidae) emergence and oviposition in Nova Scotia, Canada. The Canadian Entomologist, [online] 152(3), 374-388. http://dx.doi.org/10.4039/tce.2020.19
Plain language summary
Effective pest management relies upon knowing not only what pest is causing economic damage but when that pest is present in the crop. Monitoring for insect pests can be time consuming and costly depending upon the type of trap and lure which is required. Insect development is regulated strongly by temperature and this provides an opportunity to identify when to be in the field to start monitoring and thus reduce the amount of time and materials spent during times when the insect is not present. Carrot weevil is a pest of carrot throughout North America. In Canada, it is present in Nova Scotia, Ontario and Quebec and causes damage ranging from 30-60% depending upon the year. Adults overwinter next to or in carrot fields and start moving around in the spring seeking hosts for food and as a site to lay eggs. Control for carrot weevil is currently a pesticide application, applied when a cumulative 5 weevils are captured in traps placed in the field. In this study, we monitored carrot weevil in 15 carrot fields in Cumberland County during 2014-2016, inclusive. We then developed a model which will predict, based upon accumulated heat units (calculated using daily temperatures above a certain threshold) when 10, 50 and 90% of the population will have emerged. Growers wishing to control carrot weevil can use this model to know when the majority of the adults are present in the field to better time their pesticide application and prevent the need for a second spray.
Abstract
Carrot weevil, Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae), is a pest of carrot (Daucus carota var. sativus Hoffmann; Apiaceae) throughout eastern Canada. Carrot weevil emergence and oviposition were monitored in commercial carrot fields in Nova Scotia. Cumulative degree days were calculated using a base temperature of 7 °C (DD7), and models were developed to predict cumulative emergence and oviposition using nonlinear regression. Cumulative emergence and oviposition were adequately explained as functions of DD7 by a three-parameter sigmoidal Hill equation. Our emergence model predicted initial and peak adult emergence at 35 and 387 DD7, respectively, with oviposition on carrot baits occurring as early as 42 DD7. Models were then validated to evaluate how well they performed. Oviposition on carrot plants began at the fourth true-leaf stage (342 DD7) and continued until eleventh true-leaf stage. Growers using these models can identify their window of opportunity to manage their carrot weevil populations targeting the majority of emerged adults before oviposition begins in the field.