African Stem Borer Moth

Busseola fusca .. is also known as the Maize Stalk Borer.

The Maize Stalk Borer is an indigenous African moth that has larvae (caterpillars) that bore into grasses with thick stems. It is a pest of Maize and Sorghum, and in South Africa it is considered to reduce maize production by about 10%.

Life Cycle

- First Generation -

o Adults: Emerge from pupae in the last quarter of the year but mainly in November.

o Eggs: The female lays a batch of up to 150 eggs between the leaf sheaths and stalk. Eggs in a batch are slightly separated from one another. Females usually lay a number of egg batches and in total can lay close to 1000 eggs. Eggs hatch about nine days after they have been laid.

o Larvae: First... read more instar larvae are termed 'top grubs' and feed on young, unfurled leaves, the holes they have eaten becoming visible when the leaves unfurl. Caterpillars move between plants quite often, doing so by floating across to a new plant suspended by a silken thread. Older larvae start feeding down the inside of stalks, usually only one larva per stalk as they are cannibalistic. There are usually six larval instars but there can be as many as eight when conditions are unfavourable. In the last instar they tunnel to the outer perimeter of the stalk where they leave a very thin circular membrane of plant tissue through when the adult will be able to emerge after pupation. Larvae complete there development after about a month.

o Pupae: The larva pupates inside the hollowed out stalk. The pupal stage lasts about three weeks.


- Second Generation -

o Adults: Emergence is in the first quarter of the year, mainly February.

o Eggs: In this generation the eggs are laid along the edge of the sheathing leaves.

o Larvae: The newly emerged larvae feed on the succulent growth in the growing cob and its enveloping leaves, causing extensive damage to the young seeds. Larvae disperse to other plants and as they grow bigger they start boring into stalks, with eventually there being only one caterpillar per stalk.

o Pupae: Some of the larvae pupate in the stalk before winter and emerge as adults after about three weeks. The majority of larvae, however, pass through winter in the base of the stalk and only pupate in spring.

- Third Generation (only some individuals) -

The larvae that managed to pupate and emerge before winter emerge as adults before winter. Eggs are laid on unseasonal maize. Larvae start their development before winter and then pass through winter to pupate in spring. So it is the early starting first generation moths that usually end up going through a third generation within the development year.