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. marilandica), 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°C - 30°C. Optimal environmental conditions included at least 12 h of free moisture (dew) at 20°C - 30°C. Spray mixtures containing approximately 1.0 × 105 or more conidia·ml–1 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 in the southeastern U.S.
Highlights
Coffee senna (Cassia occidentalis L.) is a non-nodulating legume that was originally introduced as a potential crop plant [1,2]
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. marilandica), and sicklepod (C. obtusifolia) were affected by this pathogen, but 35 other crop and weed species, representing 8 botanical families were not affected
Summary
Coffee senna (Cassia occidentalis L.) is a non-nodulating legume that was originally introduced as a potential crop plant [1,2] It has escaped cultivation and has become widely distributed in the south-central and southeastern regions of the United States [3]. Its seeds have impermeable seed coats and scarification is required to allow imbibition of water, and the breaking of dormancy [3] Control of this weed is difficult because of its tolerance to many commonly used herbicides, its prolific growth habit, and emergence throughout the growing season [4,9,12,13,14]. Growth stage on biocontrol efficacy, and the host range of this pathogen Determination of these parameters is essential for evaluating this fungus as a mycoherbicide
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