Busseola fusca (African Stem Borer, Maize Stalk
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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%.
- Adults. Emerge from pupae in the last quarter of the year
but mainly in November.
- 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.
- Larvae. First 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
- Pupae. The larva pupates inside the
hollowed out stalk. The pupal stage lasts about three weeks.
- Adults. Emergence is in the first quarter of the
year, mainly February.
- Eggs. In this generation the eggs are laid along
the edge of the sheathing leaves.
- 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.
- 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.
busseolae (Hymenoptera: Scelionidae)
sesamiae (Hymenoptera: Braconidae)
attacking half-grown caterpillars. As many as 100 parasitoid larvae can
develop on one caterpillar. At the end of their development they pupate in
white silken cocoons that cover the remains of the caterpillar. They can
kill up to 95% of caterpillars late in the season.
sp. (Hymenoptera: Ichneumonidae)
furvum (Hymenoptera: Eulophidae)
Up to about 100 can emerge from one stalk borer pupa.
The predators and parasitoids play a
valuable role in bringing down the population numbers of Stalk Borer but
often not enough to satisfy the farmers.
Old stalks lying in the fields during
winter contain the overwintering caterpillars so they need to be removed or
ploughed deeply into the soil so that moths cannot emerge successfully.
Four to six weeks after moth emergence,
plants need to be checked for stalk borer larvae. Insecticides are normally
applied if more than five out of every 100 randomly selected plants contains
out more about maize pests in southern Africa
& Moran, V.C. 1982. Insects and mites of cultivated plants in South
Africa. Butterworths, Durban.
Chinwada, P. & Overholt, W.A. 2001.
Natural enemies of maize stemborers on the highveld of Zimbabwe. African
Entomology 9: 67-75.
Ebenebe, A.A., van den Berg, J. & Van der
Linde, T.C. de K. 2000. Seasonal flight activity of the maize stalk borer, Busseola
fusca (Fuller) (Lepidoptera: Noctuidae), in Lesotho. African Entomology
Ebenebe, A.A., van den Berg, J. & Van der
Linde, T.C. 2001. The incidence of Dorylus helvolus (Linnaeus)
(Hymenoptera: Formicidae) and parasitoids (Hymenoptera: Braconidae) as
mortality factors of Busseola fusca Fuller (Lepidoptera: Noctuidae)
and Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) in Lesotho. African
Entomology 9: 77-84.
Kfir, R. 2000. Seasonal occurrence,
parasitoids and pathogens of the African stem borer, Busseola fusca
(Fuller) (Lepidoptera: Noctuidae), on cereal crops in South Africa. African
Entomology 8: 1-14.