Specially, for a p + n yields delta- + delta++ + a neutral pion$p^+ + n \rightarrow \Delta^- + \Delta^{++} + \pi^0$.
I see that charge is conserved. All other conservation rules seem to check out. But, when drawing the Feynman diagram there seem to be totwo quarks that come from nowhere. Is there a virtual particle that could decay into a neutral pion?