Rainfall is a natural control agent. Young larvae are easily dislodged from plants by rain and can drown on the soil surface or in water trapped on the plants. Warm, dry weather seems to promote the build-up of high population levels. Other factors influencing diamondback moth abundance are weather conditions during the egg-laying period. Cool, cloudy weather reduces moth flight activity.
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.