Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 4, 2007
Publication Date: December 5, 2007
Citation: Boyette, C.D., Hoagland, R.E., Weaver, M.A. 2007. Effect of Row Spacing on Biological Control of Sicklepod (Senna obtusifolia) with Colletotrichum gloeosporioides. Biocontrol Science and Technology 17(9):957-967. Interpretive Summary: An isolate of the fungus Colletotrichum was evaluated in field trials in narrow row and wide row soybeans for its ability to control the weed sicklepod. Over a three year testing period, a single application of the certain formulations of the fungus controlled sicklepod similar to a herbicide standard in narrow-row soybean, while two applications were required to achieve similar levels of control in wide-row soybean plots. Without appropriate formulations the fungus was ineffective. The results in this report indicate that, when properly formulated, a single application of this fungus can effectively control sicklepod in narrow-row soybeans, and that bioherbicide efficacy can be altered by various crop management systems.
Technical Abstract: In field experiments conducted over three years, the mycoherbicidal fungus Colletotrichum gloeosporioides formulated either in an invert emulsion or with 20% (V/V) unrefined corn oil and 0.2% Silwet L-77 surfactant effectively controlled S. obtusifolia in narrow (51 cm) rows of soybean. However, in wide (102 cm) rows, one application of either formulation failed to provide season-long control of S. obtusifolia. Two applications were required for season-long weed control. In narrow (51 cm) rows, one application of the fungus either in unrefined corn oil or an invert emulsion controlled S. obtusifolia an average of over 90%, and a second application was not required for season long weed control. Soybean yields in wide-row plots treated with two applications of either the fungus/corn oil or fungus/invert emulsion, or with a single application of the fungal treatments in narrow-row soybean plots were not significantly different from weed free control plots, or from plots treated with the herbicide chlorimuron. These results suggest that row spacing can affect mycoherbicidal efficacy of this fungus for controlling S. obtusifolia.