The adverse effect of synthetic pesticides on human health and the natural ecosystem necessitate the need to explore natural mechanisms of disease control in plants. This study evaluated the allelopathic potential of five biocontrol agents: Trichoderma longibrachiatum, Trichoderma asperellum, Bacillus subtilis, Bacillus cereus and Pseudomonas fluorescens in the control of six fungal pathogens associated with tuber rot of Dioscorea cayenensis. Rotten tuber samples were randomly collected across three agro-ecological zones (AEZs): humid rainforest (HF), derived savanna (DS), and southern Guinea savanna (SGS) in Nigeria. Biocontrol agents were isolated from the yam rhizosphere using the serial dilution method; the agar pairing method was used for the in vitro trials. The destructive sampling method was used to evaluate rot control by the antagonists in vivo. Aspergillus niger had the highest incidence of 64.71% across the HF, 52.08% across the DS, and 41.98% across the SGS. B. subtilis had the highest inhibitory zone of 16.7 ± 0.05% when paired with A. niger, 15.4 ± 0.01% with Lasiodiplodia theobromae, 14.0 ± 0.33% with Penicillium oxalicum, 7.1 ± 0.14% when paired with Rhizoctonia solani; 17.1 ± 0.11% with Sclerotium rolfsii, and 10.3 ± 0.94% with Fusarium oxysporum. All biocontrol agents significantly (P = 0.05) reduced rot development of the test pathogens relative to the control in the in vivo experiment. The establishment of a distinct zone of inhibition, especially by the bacterial antagonists attests to the fact that they produced allelochemical substances. Therefore, further research is recommended to evaluate the biochemical composition of these microbial metabolites, their level of toxicity, and fate in the environment.

Damping-off (Pythium aphanidermatum) is a soil-borne disease which accounts for seedling mortality and significant yield losses in tomato production. Laboratory and screenhouse experiments were conducted in 2017, with a repeated field trial in 2018 to evaluate the efficacy of combining three biological control agents (BCAs), Trichodermaviride, T. harzianumand Bacillus subtilis with Allium sativumextract for the integrated management of the disease in tomato crop. Treatments were laid out in a completely randomized design and randomized complete block design in the screenhouse and field experiments, respectively with eighteen treatments and three replications. The BCAs and extract were formulated and applied using seed treatment and soil sprinkling methods. Treatment combinations of BCAs with A. sativumwere more effective in the reduction of mycelial growth of the pathogen with inhibitory values that ranged between 77.6-91.2% than single inoculation. Seed treatment before planting was more effective than soil sprinkle method, reducing pre-emergence and damping-off incidence to between 6.8-18.3% and 9.7-26.3% under screenhouse and field conditions, respectively than the sprinkling method. Soil sprinkle with T. harzianumin combination with A. sativumextract had the highest cumulative tomato fruit yield of 902 kg/ha-1under field conditions. This study showed that combined application of BCAs and A. sativumextract reduced damping-off disease and thereby improved the fruit yield of tomato. Bangladesh J. Agril. Res. 44(3): 553-567, September 2019

This study evaluated the effect of integrated disease management on the incidence and severity of blast disease, and growth performance of rice. Moringa oleifera extract, Trichoderma asperellum, cattle dung and a synthetic fungicide were evaluated in sixteen treatment combinations using a susceptible IRAT 109 rice cultivar. The pot experiment was laid out in a randomized complete block design with three replications at the rooftop screenhouse of the Department of Crop Protection and Environmental Biology, University of Ibadan between May and October, 2019. Treatment with combination of M. oleifera extract, cattle dung and blastforce had the lowest disease incidence and mean severity of 16.8 and 7.5%, respectively which was significantly (p<0.05) lower than the standard positive check. Inoculated plants that were treated with a combination of T. asperellum, M. oleifera and cattle dung produced the highest yield of 7.6 tons/ha relative to control. This study showed that the combined application of naturally occurring biopesticides and cattle dung was more effective than single treatment in the management of rice blast disease. Bangladesh J. Agril. Res. 45(4): 395-407, December 2020