Heavy rain can disrupt mating and egg-laying. If inclement weather persists, many female moths die before egg-laying is completed. Larvae of the diamondback moth feed on the foliage of cruciferous plants from the seedling stage to harvest. They can greatly reduce the quality and yield of the crop. Older larvae feed on flowers, young pods and the surface tissue of stems and mature pods, usually from mid-July to early August.
Most damage is caused by feeding on the surface of filling and maturing pods.
The seeds under damaged areas do not fill properly and the pods are more susceptible to early shattering. In severe cases, feeding damage shows from a distance as an abnormal whitening. After an infestation is controlled in a crop at the pod stage, there is not enough time for a new infestation to develop. Predators, including spiders and birds, may also kill the larvae and adults. Little is known about the effectiveness of these natural enemies in reducing populations.