Bifra is an annual noxious broadleaf weed of winter-sown crops in the Central Anatolia and Middle Black Sea regions of Turkey. This species has become more prevalent in wheat fields in the past three decades because of poor chemical control. Field experiments were conducted in Havza and Kavak, Samsun, Turkey, to evaluate the effect of cultivar and seeding rate on the competitive interaction between bifra and wheat at four bifra densities. Wheat grain yield increased with seeding rate, either in the presence or in the absence of bifra in both locations. Decreasing the seeding rate from 250 to 200 kg/ha or 150 kg/ha decreased wheat yield in the presence of bifra in all cultivars. The percentage yield decreases were different according to cultivars, although yields decreased in all cultivars. On the basis of the analysis of yield variables, data suggest that the relative competitiveness was ‘Bezostaja’ > ‘Momtchill’ > ‘Kate A-1’ = ‘Panda’. Bifra biomass and seed numbers were reduced not only by an increase in the wheat seeding rate but also by cultivars. Bifra seed production in Bezostaja, Kate A-1, Momtchill, and Panda were diminished 60, 53, 54, and 46%, respectively, at the seeding rate of 250 kg/ha compared with bifra alone at a density of 350 plants/ m2.
Nomenclature: Bifra, Bifora radians Bieb.; Winter wheat, Triticum aestivum L. ‘Bezostaja’, ‘Kate A-1’, ‘Momtchill’, ‘Panda’.
Additional index words: Competition, weed management, wheat cultivars.