SUMMARYApplications of 2,4-D in amounts lethal to the plant inhibited nectar secretion in poinsettias (Euphorbia pulcherrima), usually within two days. Applications of amitrole did not inhibit nectar secretion, and the nectar contained a normal amount of total sugars.The nectar secreted by plants treated with 2,4-D contained an auxin-like substance. This nectar, and nectar from plants treated with amitrole, were not toxic to mosquito larvae and are therefore unlikely to present an acute danger to honeybees.Plants subjected to foliar applications of 2,4-D-1-C14and amitrole-5-C14produced radioactive nectar. The radioactivity in nectar from plants treated with 2,4-D was located in a substance very similar to 2,4-D, but its identity has not yet been determined. Amitrole was not secreted into nectar by poinsettias which had received foliar applications of amitrole.