THE EFFECTS OF SWEETCLOVER SPECIES, CULTIVARS, AND NITRATE FERTILIZERON FEEDING BY THE SWEETCLOVER WEEVIL, SITONA-CYLINDRICOLLIS FAHRAEUS (COLEOPTERA, CURCULIONIDAE)

Sweetclover, Melilotus Miller, was planted in a field near Saskatoon, Saskatchewan, to determine the effects of species and cultivars on ear ly season feeding by the sweetclover weevil, Sitona cylindricollis. Th e wild annual species M, infesta Cuss. was consumed less than were cul tivars of M. alba (Desr.), which were generally consumed less than cul tivars of M. officinalis (L.). The amount of feeding injury by the wee vil among nine sweetclover entries was not significantly correlated wi th nitrate levels in cotyledons, unifoliolate, or first trifoliolate l eaves. Weevils fed equally well On entries with high and low coumarin levels. Results from greenhouse cultivar trials generally paralleled t hose from the field. In an experiment in which different levels of amm onium nitrate fertilizer were broadcast prior to seeding of M. officin alis cultivar Norgold, levels of nitrate ion in the foliage were signi ficantly correlated with fertilizer regime, but not with damage indice s of the weevil. These experiments suggest that the nitrate ion in iso lation is not the principal factor in the deterrence to sweetclover we evil feeding in M, infesta, and that elevating nitrate levels in sweet clover leaves would not confer resistance to this insect.