FECUNDITY OF THE ROOT WEEVILS BRACHYRHINUS SULCATUS AND SCIOPITHES OBSCURUS ON STRAWBERRY AT DIFFERENT CONDITIONS OF HOST PLANT NUTRITION

Abstract

Field applications to strawberry of nitrogen, phosphorus and potassium had no significant effect on the fecundity of the obscure root weevil, Sciopithes obscurus Horn, fed on detached leaflets in the laboratory, but when nitrogen was not applied there was a significant reduction in the fecundity of the black vine weevil, Brachyrhinus sulcatus (F.). With strawberry in sand culture, low levels of nitrogen had no apparent effect on the fecundity of S. obscurus but were associated with a significant reduction in the fecundity of B. sulcatus. Some association is suggested between the different effects of nitrogen nutrition on these species and their different susceptibilities to cyclodiene insecticides.