Grain Borer

Prostephanus truncatus

Appearance

•  Brown body colour. 2.2 to 4.3 mm in length.
•  Antennae have 3 large segments at the end forming visible antenna clubs, reddish in colour.
•  The humped thorax covers the head, its front rim has teeth-like indentations.
•  Elytra (wing covers) are heavily punctated and drop off sharply at the back, giving the impression of a square end when seen from above.

Lifecycle

•  The female lays an average of 10 eggs on a grain of maize and the hatched larvae bore into the grain.
•  The larva undergoes up to 4 development phases and pupates inside the corn grain.
•  Lifecycles can be quite short, in good conditions (25 days at 34 °C, 75% relative humidity) there are several generations per year.

Habits

•  Adult beetle is a pest of stored maize, but also infests other types of grain.
•  Larva bores tubular passages into the grain, typically making one main tunnel with smaller ones branching off.
•  Brought in from tropical Central America in cassava roots and tapioca products, as well as in starchy fruits and tubers.