Submitted to: Biocontrol
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/6/2006
Publication Date: 9/20/2006
Citation: Boyette, C.D., Jackson, M.A., Bryson, C.T., Hoagland, R.E., Connick Jr, W.J., Daigle, D.J. 2006. Sesbania exaltata biocontrol with Colletotrichum truncatum microsclerotia formulated in ‘Pesta’ granules. Biocontrol. DOI 10.1007/s10526-006-9031-7. Interpretive Summary: Hemp sesbania (Sesbania exaltata) is a problematic weed in soybeans throughout much of the southeastern U.S. An isolate of the fungal pathogen Colletotrichum truncatum (NRRL 18434) has shown promise as a bioherbicide for controlling this weed. In addition to producing spores, the fungus also produces survival structures called microsclerotia that are more durable than spores. Microsclerotia were mixed with kaolin and wheat flour and formulated into granules called 'Pesta.' This formulation effectively controlled hemp sesbania when applied pre-emergence to weeds, or incorporated into the soil at rates of 168 kg/ha or 336 kg/ha. This formulation is highly stable in storage at 40C and remains viable for at least 7 years. The results in this report indicate that, when properly formulated, Colletotrichum truncatum (NRRL 18434) can be a very effective bioherbicide for controlling hemp sesbania.
Technical Abstract: [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill] (hemp sesbania) was effectively controlled in soybean [Glycine max (L.) Merr.] field test plots over a two-year testing period (1995-1996) with microsclerotia of the bioherbicidal fungus Colletotrichum truncatum formulated into wheat gluten-kaolin granules called 'Pesta'. Weed control averaged 84% and 88%, respectively, in plots treated preplant incorporated (PPI) at 'Pesta' rates of 168 kg ha-1 or 336 kg ha-1, and 71 and 78%, respectively, in plots treated preemergence (PE) at 'Pesta' rates of 168 kg ha-1 or 336 kg ha-1 over the testing period. Postemergence (POE) control averaged 30% and 50%, respectively, for the 168 kg per ha and 336 kg ha-1 treatments, and was significantly less effective than either PE or PPI treatments. Although pathogenesis and mortality occurred in hemp sesbania tissuses, satisfactory weed control was not achieved in plots treated at rates of 17 or 84 kg ha-1 with any of the application methods. Soybean yields were significantly greater in test plots treated PPI or PE, as compared to yields from test plots treated either POE, with inert 'Pesta' granules, or from untreated controls. These results suggest that microsclerotia of C. truncatum formulated in 'Pesta' granules offers an effective method for controlling this important weed.