Title: Biological control potential of Colletotrichum gloeosporioides for coffee senna (Cassia occidentalis) Authors
Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 4, 2011
Publication Date: April 1, 2012
Citation: Boyette, C.D., Hoagland, R.E., Weaver, M.A., Stetina, K.C. 2012. Biological control potential of Colletotrichum gloeosporioides for coffee senna (Cassia occidentalis). American Journal of Plant Sciences. 3:430-436. Interpretive Summary: Coffee senna, an economically important weed in the southeastern U.S., is difficult to control with chemical herbicides. A fungal pathogen was isolated from seedlings of this weed and found to produce spores readily on solid and liquid media. Coffee senna, wild senna and sicklepod were infected and killed by this pathogen, but many other crop and weed species, were unaffected. Coffee senna seedlings at early growth stages were the most susceptible to this fungus. At least12 h free moisture (dew) at 20-30 C were required for maximal bioherbicidal activity. Weeds were also controlled under field conditions. Results suggest that this fungus has potential as a bioherbicide to control this serious weed.
Technical Abstract: A fungal pathogen, Colletotrichum gloeosporioides was isolated from a greenhouse-grown seedling of coffee senna (Cassia occidentalis) and evaluated as a mycoherbicide for that weed. Host range tests revealed that coffee senna, wild senna (C. pilosa),and sicklepod (C. obtusifolia) were also affected by this pathogen, but 35 other crop and weed species, representing 8 botanical families were not affected. The fungus sporulated prolifically on solid and liquid media with maximum spore germination and growth occurring at 20-30 C. Optimal environmental conditions included at least 12 h of free moisture (dew) at 20-30 C. Spray mixtures containing approximately 1 x 105 or more conidia per milliliter gave maximum control when coffee senna seedlings were sprayed until runoff occurred. Coffee senna seedlings that were in the cotyledon to first-leaf growth stage were most susceptible to this pathogen. Weed control efficacy studies under field conditions demonstrated that control of coffee senna was directly proportional to the inoculum concentration applied. Results of these tests suggest that this fungus has potential as a mycoherbicide to control coffee senna, a serious weed pest in the southeastern U.S.