Thomas Reed and Patrick McCullough, University of Georgia - Griffin, Griffin, GA
Aminocyclopyrachlor is a broadleaf herbicide currently labeled for use in roadside turfgrass. In previous research, aminocyclopyrachlor has shown potential efficacy for controlling smooth crabgrass in tall fescue but results were inconsistent based on application timing and growth stage. The objective of this research was to evaluate the influence of growth stage on smooth crabgrass control with aminocyclopyrachlor compared to quinclorac and fenoxaprop. Aminocyclopyrachlor was applied at 0, 53, 79, or 105 g a.i/ha and compared to quinclorac at 840 g a.i./ha or fenoxaparop at 100 g a.i./ha to a tall fescue field seeded in mid-April in Griffin, GA. Treatments were applied at a multi-leaf or multi-tiller timing of the smooth crabgrass population. Aminocyclopyrachlor at 53 and 79 g a.i./ha provided poor control (<70%) of smooth crabgrass at the mulit-leaf and multi-tiller growth stages. Aminocyclopyrachlor at 105 g a.i./ha provide fair (70 to 79%) control of smooth crabgrass at both application timings and was comparable to quinclorac and fenoxaprop. Aminocyclopyrachlor at all rates was less injurious than fenoxaprop to tall fescue seedlings on one date but injury was always acceptable (<20%).