You don't need to overdo it. Your soil may be fine as is. Their rasping mouth parts do all the damage, lacerating the plant tissue at the segment edges of undeveloped buds, forming within the fans before the scape emerges. Buds are sometimes so damaged that they look as if small zippers had been sewn into the edges of petal and sepal. Flowers are unable to open properly and are deformed and contorted.
Scapes are sometimes so damaged that seed pods often dry and break off before the pod matures.
Repeat spraying may be necessary within a short time if the infestation is heavy, as the scape elongates and buds develop. Any other sucking insect will likely be destroyed as the expanding tissue continues to carry the systemic chemical.