Comparative Effects of Different Maize Cropping Systems on the Management of Spodoptera frugiperda (Lepidoptera: Noctuidae), in Smallholder Farming Systems in Benin.

Abstract:

The Spodoptera frugiperda (Lepidoptera: Noctuidae), commonly known as the fall armyworm (FAW), is a highly invasive pest that threatens diverse cropping systems worldwide, particularly maize-based systems in sub-Saharan Africa. Intensive reliance on synthetic insecticides has raised concerns regarding human health risks, environmental contamination, and disruption of natural enemies. This study evaluated whether maize intercropping with edible legumes, combined with botanical and biological treatments, could reduce FAW infestation and improve yield under field conditions in five municipalities of Benin during the 2025 rainy season. Nine treatments were tested: (i) maize monoculture with standard agronomic practices (control), (ii) maize–soybean treated with cashew balm, (iii) maize–groundnut treated with BotaniGard 22WP, (iv) maize–cowpea treated with Ricinus communis extract, (v) maize–mucuna treated with Thevetia neriifolia extract, (vi) maize–sorghum treated alternately with cashew balm and BotaniGard 22WP, (vii) maize monoculture treated with TopBio, (viii) maize monoculture treated with salt plus crushed charcoal, and (ix) the Push–Pull technique. Data collected included FAW infestation symptoms, severity scores, larval density, and maize yield. Results indicated that several treatments significantly influenced infestation severity. The untreated control exhibited the strongest effect, increasing by more than fourfold the probability of belonging to a higher severity category (OR = 4.27; 95% CI: 3.25–5.61; p < 0.001). In contrast, the MSB (OR = 1.27; p = 0.092) and MSBB (OR = 0.84; p = 0.22) treatments showed no significant effect on severity. All tested treatments significantly reduced mean larval counts compared with the control plus agronomic practices (p < 0.05). The most pronounced reductions were observed with CS+A (IRR = 0.27), MSBB+A (IRR = 0.29), and MT+A (IRR = 0.37), corresponding to larval decreases exceeding 60%. Notably, MT+A significantly increased maize yield by 0.28 t ha⁻¹ (p = 0.018). Overall, maize intercropping with edible legumes and the Push–Pull strategy significantly reduced FAW infestation compared with maize monoculture. These approaches represent promising, environmentally sustainable components of integrated FAW management in African smallholder systems.