Pebble flux at 1 au and dust trap blocking efficiency ℬ as a function of time for simulations with or without planetesimal formation. We focus on the case of a gap carved by a 100 M_⊕ planet at 10 au, in which case only three simulations reach the requirements for planetesimal formation (δ_turb = 10⁻⁴ and α_visc ∈ [10⁻³, 3.2 × 10⁻³], see Fig. 8). We see that highly blocking dust traps (ℬ > 0.9) can only be achieved thanks to planetesimal formation. If planetesimals did not form, a dust trap in the same disc conditions would be much leakier.