In 1984, BASF Wyandotte Corporation Market Development representatives conducted studies to evaluate: 1) spray volume effects on the efficacy of sethoxydim (Poast) in annual and perennial grasses; 2) the potential of total post emergence grass control in cotton.

Poast was applied at 0.2 lb. ai/A in 5 and 20 gallon per acre (gpa) spray volumes to evaluate the control of annual grasses and rhizome johnsongrass in cotton. At two weeks after application, no differences were observed in control of seedling johnsongrass (Sorghum halepense) and goosegrass (Eleusine indica) (100% and 90% control respectively) at either spray volume. Differences were observed on browntop panicum (Panicum fasciculatum) control. Better control was observed at two weeks on 4 to 8" (98 vs. 85%) and 8 to 12" (90 vs. 70%) grass when Poast was applied in 5 gpa compared to 20 gpa. At six weeks, only the 8 to 12" grass indicated a slight advantage to the lower spray volume (8% better control). On moderately drought stressed broadleaf signalgrass (Brachiaria platyphylla), control from Poast in 20 gpa was poor (20%) compared to excellent control (100%) in 5 gpa.

Control of rhizome johnsongrass 15 to 30" tall was improved when the application was lowered to 5 gpa compared to 20 gpa. The two-week evaluation showed control to be 10% more with the 5 gpa (90 vs. 80%) while the six-week evaluations averaged 23% better control with 5 gpa spray volume (88 vs. 65%).

Eight studies were conducted to determine if reduced spray volumes would effect Poast activity and the control of bermudagrass (Cynodon dactylon). The rate of Poast and oil was held constant at 0.3 lb. ai/A and 1 qt. respectively, while the spray volumes were 20, 10, 5 and 1 gpa. No significant difference was noted between the various spray volumes tested, and excellent control of bermudagrass, with runners less than 12 inches, was observed.

Season long control of grasses is possible with only post emergence herbicides. Broadleaf weed control with only post emergence herbicides may not always be acceptable. Pre-emergence herbicides combined with post emergence herbicides effectively control annual broadleaf weeds and grasses.