Causal agent(s) and transmission
The European corn (stem) borer (Ostrinia nubilalis) belongs to the order Lepidoptera and has a greyish-yellow coloured larvae (2 cm long). The larvae are dark-headed, with six small brown plates on each segment, each bearing a thread of silk (photo 1). They can be found mining inside the stems of various crops such as maize, beans, tomatoes and sometimes potatoes. The larvae penetrate inside the stems which can easily be broken. When these insects are numerous, damage can be quite visible causing significant destruction to the crop.
The European corn borer usually has one generation per year but, in warm areas, this can double, as for example in the South of France.
Adult females of the European corn borer lay clusters of eggs on (corn) leaves, usually on the underside. Overwintering occurs inside the stem of host plants as diapausing (fifth stage) larvae.
Another similar species, Hydroecia micacea, sometimes called the potato corn borer, may also bore at the base of stems and cause damage to potato plants.