SITONA WEEVILS (COLEOPTERA, CURCULIONIDAE) AS AGENTS FOR RAPID TRANSFER OF NITROGEN FROM WHITE CLOVER (TRIFOLIUM-REPENS L) TO PERENNIAL RYEGRASS (LOLIUM-PERENNE L)

The effects of root feeding by larvae of Sitona hispidulus (F.) (a common weevil pest of white clover) on the rate of transfer of nitrogen between plants of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) were investigated using a nutrient slant board technique. Clover plants, labelled with N-15 were grown adjacent to ryegrass plants and were either infested with Sitona larvae or not infested. Ryegrass plants associated with the infested clover plants had a significantly higher dry matter yield and nitrogen content (75% and 74% respectively) than the uninfested plants, after 33 days exposure to insect herbivory. It was concluded that root feeding insects could play an important role in the cycling of nitrogen in grass/clover swards.