Pesticidal Potential and Selectivity of Soybean Extract on Pests and Non-Target Insects of Cocoa

With the search for alternative pest management strategies due to the concerns associated with synthetic pesticides, botanicals have been of increasing interest. However, the potential of plants such as soybean (Glycine max) as biopesticides is less known. Hence, this study assessed the activity of soybean extract (SBE) on insects and Phytophthora pod rot pathogens of cocoa using the filter paper contact toxicity and amended-agar plate techniques, respectively. Concentrations of 0.001–100% w/v SBE induced a mortality of 17.02–100% on the cocoa mirid Sahlbergella singularis and 2.5–90% and 5.26–100% on the ants Crematogaster africana and Pheidole megacephala, respectively. Also, 0.001–20% w/v SBE inhibited mycelial growth by 0–72% (Phytophthora palmivora isolates) and 1.17–81.03% (Phytophthora megakarya isolates). The minimum inhibitory concentration for P. palmivora and P. megakarya isolates was 1% and 0.001% w/v SBE, respectively. The median lethal concentration was 3.50% (S. singularis) and 193.73% w/v (C. africana), while the median inhibitory concentrations were 4.70 and 7.87% (P. palmivora isolates) and 1.13 and 1.48% (P. megakarya isolates). The activity of SBE on the pests was differential but non-toxic to the ant C. africana. The findings indicate the potential of SBE as a biopesticide against S. singularis and Phytophthora pod rot pathogens of cocoa.