Evaluation of the herbicidal potential of some fungal species against Bidens pilosa, the coffee farming weeds

Weeds are the most productive limiting factor, especially in organic farming systems where the uses of synthetic herbicides are not allowed due to their negative impacts. Hence, synthetic herbicides need to be replaced with biological herbicides for weed management. Thus, the present study was designed to evaluate the herbicidal activity of conidia suspensions from Aspergillus niger, Trichoderma asperlium, Trichoderma atroviride, Trichoderma hamatum, Trichoderma harzanium, Trichoderma longibrachatum and Trichoderma viride against Bidens pilosa weed via a series of laboratory and lath-house conditions that laid out in a CRD and RCBD, respectively, with three replications for each bioassay. The results revealed that all fungi, except T. longibrachatum, had significantly reduced seed germination as well as early growth of the target weed compared to the untreated control. The inhibitory effects were measured to be varied among the types of conidia suspensions of fungal species and their level of concentration. The highest rate of inhibition was observed for conidia suspension from A. niger which suppressed with the maximum seed germination inhibitory level (65%) over control. Likewise, the plumule and radicle growth length of the target weed also significantly inhibited by the tested fungi (ranging from 10 to 85% and 34 to 97%) compared to the control, respectively. Based on their efficacy in the laboratory bioassay, the herbicidal potential of selected fungi was further evaluated in pot experiments. In contrarily to laboratory observations, the effect of different fungal conidia suspensions on various growth parameters of the targeted weed was insignificant in the lath-house experiments. In conclusion, the application of A. niger displayed some potential green light to be investigated as a biocontrol agent with promising retarding in the germination and early growth of B. pilosa. Hence, we recommend further investigation of those fungi under field conditions on different coffee weed species.