Fluazifop Toxicity to Quackgrass (Agropyron repens) as Influenced by Some Application Factors and Site of Application

Abstract

The phytotoxicity of the butyl ester of fluazifop to quackgrass was enhanced by the addition of a nonionic surfactant and an oil additive either alone or in mixture to the spray solution. The enhancement caused by the surfactant was consistently greater than that caused by the oil additive. A higher level of quackgrass control was achieved at the carrier volumes of 100, 200, or 400 L/ha, than at 800 L/ha. Quackgrass growth inhibition was greater following application of small herbicide droplets which averaged 0.25 μl compared to larger herbicide droplets at each herbicide application rate. When droplet concentration was varied and different doses of the herbicides applied to plants, no significant differences were noted at the highest dose. However, at intermediate dose treatments, the least concentrated droplets (2.5 μg/μl) were most phytotoxic. Herbicide droplets placed at basal areas of leaves were more phytotoxic than when placed at lamina apices and middle areas. This effect was most pronounced on adaxial rather than abaxial surfaces. In general, application of droplets to younger leaves resulted in greater phytotoxicity than treatment of older leaves.