ADJUVANTS ENHANCE THE BIOLOGICAL CONTROL POTENTIAL OF AN ISOLATE OF COLLETOTRICHUM GLOEOSPORIOIDES FOR BIOLOGICAL CONTROL OF SICKLEPOD (SENNA OBTUSIFOLIA)

Authors: Boyette, Clyde

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2006
Publication Date: 6/30/2006
Citation: Boyette, C.D. 2006. Adjuvants Enhance the Biological Control Potential of an Isolate of Colletotrichum Gloeosporioides for Biological Control of Sicklepod (Senna obtusifolia). Biocontrol Science and Technology. 16:1057-1066.

Interpretive Summary: The fungus Colletotrichum gloeosporioides (NRRL #21046) was originally isolated from coffee senna and shown to be a weak pathogen of sicklepod, one of the most economically important weeds in the southeastern U.S. A process was developed to extend the host range and virulence of this bioherbicidal fungus through formulation-based approaches. When spores of the fungus were emulsified with unrefined corn oil or an invert emulsion, sicklepod control was greatly enhanced. These formulations also reduced the dew period requirements for maximum weed infection and mortality from 16 h to 8 h, delayed the need for free moisture for greater than 72 h, and enabled the pathogen to infect and kill weeds in larger (>5 leaf) growth stages. These results indicate that, when properly formulated, C. gloeosporioides NRRL No. 21046 can be a very effective bioherbicide for controlling sicklepod.

Technical Abstract: In greenhouse experiments, unrefined corn oil, Silwet L-77, and an invert emulsion were tested as adjuvants with the mycoherbicidal fungus Colletotrichum gloeosporioides, a weakly virulent pathogen of sicklepod (Senna obtusifolia). A 1:1 (V/V) fungus/corn oil tank mixture containing 0.2% (V/V) Silwet L-77 surfactant reduced the dew period requirements for maximum weed infection and mortality from 16 h to 8 h, and delayed the need for free moisture for greater than 72 h. This formulation also resulted in the ability of the pathogen to infect and kill weeds in larger (>5 leaf) growth stages. The invert emulsion resulted in similar effects upon these parameters. These results suggest that invert emulsions, unrefined corn oil and Silwet L-77 surfactant greatly improve the bioherbicidal potential of this pathogen to control of sicklepod, a serious weed pest in the southeastern U.S.