Do cultivar and burning affect forage yield and incidence of verticillium wilt or insect pests in alfalfa stands?
Alfalfa (Medicago sativa L.) is one of the most important forage crops in Canada and many parts of the world. Two experiments were conducted over a 13-yr period (1989–2002) in Lethbridge, Alberta, Canada with five alfalfa cultivars. In the first experiment, ‘Barrier’ and ‘Pacer’ were given three burn treatments (no burn, burn every year, and burn in alternate years) while in the second experiment four cultivars ‘Barrier’, ‘Heinrichs’, ‘Trumpetor’, and ‘Legend’ were given burn or no burn treatments to determine the impact of burning of crop residues on forage yield, incidence of verticillium wilt, and insect pest abundance. Burning did not affect forage yield or incidence of verticillium wilt of alfalfa. Barrier had the highest yield and lowest disease incidence. Burning had a significant albeit variable impact on abundance of alfalfa plant bugs, lygus bugs, aphids, and leafhoppers but not on abundance of alfalfa weevil. The lack of effectiveness of the burning treatments on forage yield and adverse environmental consequences of burning such as air pollution, hazardous loss of visibility during burning operations, and loss of crop cover suggest that burning should not be used as a production strategy for this widely grown crop.