The diamondback moth or cabbage moth (Plutella xylostella) is a migratory moth. Originally found in Europe, it spread out to the American, Asian and Australian continent and New Zealand. This dispersal is quite remarkable since the moths are weak fliers. They only fly small distances, but because they are very small, they cover great distances on wind energy. I found them to be rather quick in flying small distances, especially while I tried to study and photograph them.
In some areas diamondback moths are considered pests. In particular in areas where cruciferous vegetables (cabbage, kale, collard, mustard etc.) are cultivated. All cruciferous plants can become hosts to larvae of diamondback moths, but they do have preferences. Once an egg has hatched, the larva eats its way into the leaf of the plant. It makes small ‘mines’ which can be seen as round patches in the leaf. If numerous larvae are present, the plant’s growth is disrupted and flowers can’t be formed. Interestingly, a large group of moths are resistant to insecticides, even the insecticides that are normally effective against moths. In contrast, simple rainfall can be lethal for young larvae.
Because diamondback moths are considered pests, a lot of research has been conducted on life cycle, ecology and relationships between hosts-moths, moths-natural enemies and possible interactions between hosts and natural enemies of the moths. The latter interaction is quite nifty: plants affected by diamondback moths produce specific (volatile) substances which lure natural enemies of the moths to the plant, so they can deal with the discomfort of the plant (in this case the larvae of the moth). Natural enemies include certain species of parasitic wasps and stink bugs. Below is a short video how a parasitic wasp attacks a larva of the diamondback moth.