The major weedy biotypes of proso millet (Panicum miliaceum) in Canada

Abstract

Proso millet, Panicum miliaceum L., has become a problem weed in corn-growing areas of Canada over the last 15 years. Several different biotypes of this weed exist, and one of the features by which they may be distinguished from one another is seed colour. Those plants with dark olive – bronze – black seeds that shatter readily are the most difficult to control. Part of their success as weeds is due to their ability to form a long-term viable seed bank in the soil, making quick elimination from an area impossible. Other biotypes closely resemble crop types and have little dormancy or ability to form a long-term seed bank. Between these two extremes are 'crown' and some 'golden' biotypes, some populations of which have weedy characteristics that may make them more aggressive weeds as the selection process continues. Some biotypes are more readily controlled than others by a combination of management practices, including rotation and spraying. Good chemical control is available for use in some broad-leaved crops (e.g., soybeans), but consistently effective control of this weed in corn has not yet been achieved. Thus, a knowledge of the ecology of the weed can assist in other forms of management. Each biotype that has been discovered in Canada is described and illustrated, together with an outline of ecological characteristics that may aid in its identification and control.