EMERGENCE AND SURVIVAL OF HORSEWEED (CONYZA-CANADENSIS)

Horseweed emergence and survival were evaluated in no-tillage soybean and corn at Rosemount, MN, and Ames, IA, from the fall of 1992 through the summer of 1995. Most of the horseweed at both locations emerged i n the fall. Winter survival of fall-emerged seedlings ranged from 53 t o 91%. Timing and extent of horseweed emergence in spring varied by ye ar and location. Spring emergence ranged from 5 to 32% of total emerge nce, with greater spring emergence at Rosemount than at Ames. Emergenc e occurred as late as early June at Rosemount and late May at Ames. Re sults indicated that horseweed may emerge well into the growing season , and spring emergence should be considered in weed management systems for no-tillage crop production.