FECUNDITY OF THE ROOT WEEVILS BRACHYRHINUS SULCATUS AND SCIOPITHES OBSCURUS ON STRAWBERRY IN THE LABORATORY AND OUTDOORS

Abstract

The effects of laboratory and outdoor conditions on fecundity were compared between the introduced black vine weevil, Brachyrhinus sulcatus (F.), and the native obscure strawberry root weevil, Sciopithes obscurus Horn. Both species are economic pests of strawberry in the coastal area of British Columbia, Washington, and Oregon.Though B. sulcatus is much more fecund than S. obscurus both in the laboratory at a constant 20 °C and outdoors, it is not so well adapted to British Columbia conditions as S. obscurus which has a lower temperature threshold for oviposition and, therefore, a longer oviposition period.When the night temperature in cabinets at diurnal temperature programs is minimal at 8 °C, the fecundity of these nocturnal species is maximal at day temperatures of 20° for S. obscurus and 25 °C for B. sulcatus. Under these diurnal conditions B. sulcatus is the more fecund of the two and survives better in continuously high rather than variable relative humidity. S. obscurus is comparatively indifferent to humidity fluctuations.