Efficacy of Urtica spp. extract as botanical for sustainable management of soybean insect pests

Insect pests remain a major constraint to soybean (Glycine max (L.) Merr.) productivity in tropical agroecosystems, where high pest pressure and dependence on synthetic pesticides raise environmental and health concerns. The objective of this study was to evaluate the efficacy of a newly developed botanical biopesticide, Adamfo Pa (Urtica spp.), for managing soybean insect pests in Ghana. The study was conducted in the Semi-Deciduous Forest and the Savannah-Transition ecozones of Ghana. Treatments included extracts of Adamfo Pa (Urtica spp.) applied weekly and bi-weekly, and five pest management formulations at rates of 0, 300, 400, and 500 ml 100 L-1 of water, and a reference check Bypel. The rate of Adamfo Pa application significantly reduced pest populations, particularly pod-sucking bugs and defoliators, by up to 49.2 - 67%. The highest application rates (400 and 500 ml 100 L-1 of water) consistently outperformed the lowest rate (300 ml 100 L-1 of water). They were comparable to Bypel in reducing pest density, leaf damage, and overall infestation levels across both agroecological zones. Treatments with Adamfo Pa also resulted in marked reductions in pod-sucking bug density. Weekly application was more effective than bi-weekly application, especially in the Semi-Deciduous Forest ecozone, where pest pressure was higher. Strong positive relationships were observed among pest infestation parameters; namely, pest infestation versus leaf damage, pest infestation versus pod sucking bugs, pest infestation versus number of unfilled pods, filled pods versus grain yield, and pod weight versus grain yield, confirming that effective suppression of pod-sucking bugs is critical for yield protection. Location-specific responses underpinned the influence of agroecological conditions and baseline pest pressure on botanical pesticide performance, highlighting the need for site-adapted pest management strategies.