Scientific name: Busseola fusca (Fuller)
Common name: Maize Stalk Borer
Ethiopian name: Ageda Korkur
Main hosts: Maize, Sorghum
Alternative hosts: Sugarcane, Many species of grasses and cereals
IMPORTANCE IN ETHIOPIA:
Major pest of: Maize, Sorghum
DISTRIBUTION IN ETHIOPIA:
Between 1200 and 2600 meters above sea level, with increasing importance at the higher altitudes.
The leaves of young plants have holes and “windows”. When the attack is severe, the central leaves die. In older plants, the caterpillars of the first generation bore in the main stem. Some second generation caterpillars bore in the cobs.
Damage to sorghum is usually less serious than damage to maize, because sorghum easily tillers and this can partly compensate for the damage.
INSECT BIOLOGY & RECOGNITION:
Egg: The eggs are white first, but they turn darker when they get older. They are globular and about 1 mm in diameter. Eggs are laid in a long column stretching up the stem, under a leaf sheath. They hatch after about 10 days.
Larva: The young larvae are deep purple or black in colour. They crawl up the plant into the funnel. The early stages of the caterpillars feed on the leaves in the funnel of the plant. This results in characteristic lines of holes and “windows”. When the attack is severe, the shoot may turn yellow and die. If the plant dies, the caterpillars will move to another plant. If the plant survives, the later stages of the caterpillar will bore into the stem and feed there on the central tissue of the stem. The larval period takes 35 days or more. When fully grown the caterpillars are up to 40 mm long. They have a pinkish white colour and small black spots along the sides of the body. The mature caterpillar cuts a hole in the stem before pupating within the tunnel. Eventually the moth will use this hole to emerge.
Pupa: The pupa is brown and about 25 mm long. The pupal stage of the first generation will last for about 2 weeks. Before the crop ripens there are usually 2 generations. Some of the 2nd generation eggs may be laid on the cob. The caterpillars will feed on the cob, but usually move into the stem when fully grown. Before pupating they will go in a long diapause which lasts until the next rains. Then they prepare a pupal chamber in the stem and pupate.
Adult: The adult is a pale brown nocturnal moth with a wingspan of 35-40 mm.
Stems and damaged cobs should not be left in the field. They might contain diapausing larvae which will be a source of infestation for the next crop. Crop residues should therefore be burnt, deeply buried, or fed to cattle. If stalks are to be dried for use as building materials, fuel, or other purposes, it is recommended to thinly spread them horizontally in the open field for several weeks. This will reduce the survival of diapausing caterpillars.
Observe a closed season of at least two months. When there are few hosts to feed on, this will prevent the continuity of the pest population.
Plant the crop as soon as possible after the rains begin and try to plant the whole crop in the area at the same time.
Thick stemmed grass weeds should be destroyed because they might serve as alternative hosts.
During the first six weeks of growth, pull out all plants with “dead hearts” and destroy them.
Crop rotation is recommended.