NECTAR SUGAR PRODUCTION IN ALFALFA FIELDS TREATED WITH SEVERAL HERBICIDES

Field studies were conducted at three sites in northeastern Saskatchew an to determine the effects of several herbicides applied in late fall or early spring on nectar sugar production in alfalfa (Medicago sativ a L.) grown for seed. In general, sugar production was not affected de trimentally by the herbicides, but at one site alfalfa treated annuall y with metribuzin for 4 yr at the break of winter dormancy produced fl owers in early July containing significantly less nectar sugar than fl owers of plants not treated with herbicide. Increases in nectar sugar production sometimes occurred. At one site, chlorsulfuron at 0.11 kg h a(-1) or more, hexazinone at 1.0 kg ha(-1) and dichlobenil at 2.4 kg h a(-1) increased nectar sugar production in early August. Herbicide eff ects were not consistent among sites, and it seems unlikely that leafc utter bee (Megachile rotundata Fabr.) cocoon production will be affect ed significantly by these weed control practices.