SIZE-DEPENDENT ROOT HERBIVORY ON CYNOGLOSSUM-OFFICINALE

The weevil Ceuthorhynchus (Boraginobius) cruciger was the most important root herbivore of the biennial herb Cynoglossum officinale in Meijendel, The Netherlands. Only a few other species were found, but always in less than 5% of the plants. The infestation level of flowering plants of C. officinale was 22% in 1988, 56% in 1989 and 61% in 1990; in rosettes 0% in 1988 and 6% in 1989. Weevil attack was size-dependent: weevils preferred large plants over small plants and, when controlling for size, flowering plants over rosettes. Attack by the weevil significantly reduced seed production in C. officinale: the number of seeds produced per unit of plant weight as well as seed weight per unit of plant weight were smaller for the attacked plants.