Hi, welcome to GoY, it seems a bit early for this problem, but you have a choice of treatments, you can use pheromone traps, which may, or may not catch enough male moths, to prevent females laying eggs, or to indicate when the moths are busiest, so that will give an indication of when to spray with insecticide, or you can just use insecticide about mid june, you can use Bayer sprayday greenfly killer, or westland plant rescue fruit and vegetable bug killer, Derek.