Alternating Bang-Bang Biocontrol Regimes for Optimized Banana Yield under Nematode Pressure

International audience Banana and plantain production is severely threatened by Radopholus similis, a parasitic nematode that lives and propagates within plant roots, causing substantial damage and making effective control particularly challenging. Building on a recently introduced and analyzed model, we upgrade the framework to account for the combined effect of two biological control levers against Radopholus similis: a biostimulant effort reducing infestation rate, and a biopesticide effort directly lowering nematode density. To investigate the most effective biocontrol strategies, we formulate an optimal control problem and derive first-order necessary conditions using Pontryagin's Maximum Principle. The problem is solved numerically via direct methods using Bocop, yielding bang-bang-type solutions where the two controls are activated in a quasi-alternating pattern. We further compare this optimal strategy with a structured periodic control policy, showing that it provides close performance with simpler implementation.