For the monocarpic, short-lived perennial C. officinale, the probability that a plant will flower in a given year depends on plant size. Only rosettes that reach a threshold size at the end of the vegetative period in autumn will flower the following spring. During 1996, median threshold sizes for four field populations ranged from 0.96 g to 2.18 g plant dry weight. The weevil Mogulones cruciger is the dominant below-ground herbivore of C. officinale in Central Europe. During 1996, late season infestation levels ranged from 11.6% to 50.9% in four continental European C. officinale populations. M. cruciger infestation accelerated the flowering of C. officinale. At two field populations, plants infested with weevil larvae flowered at median plant dry weight threshold sizes that were 0.204 g and 0.419 g smaller, respectively, than those for uninfested plants within the same populations. Thus, infestations with M. cruciger larvae during late summer is expected to alter the size and the age structure of C. officinale populations. M. cruciger was introduced in 1997 to C. officinale in Canada. In the United States the permission for field releases is pending.
Keywords: Houndstongue, Biological control
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA