Field Experiments on the Effects of Grazing by a Chrysomelid Beetle (Gastrophysa Viridula) on Seed Production and Quality in Rumex Obtusifolius and Rumex Crispus

SUMMARY (1) Three experiments were set up to examine the effects of grazing by Gastrophysa viridula on seed production, size and germination rate in Rumex obtusifolius and R. crispus. (2) Two experiments involved established plants in the field. The third experiment used plants grown from seed and subsequently planted out of doors. (3) Both seed number and seed dry weight were significantly reduced in the grazed plants of R. obtusifolius. (4) Seed numbers of R. crispus were not significantly affected, but seed dry weight was significantly reduced in one case. (5) The proportion of lighter seeds germinating was not significantly lower than that of normal seeds.