African Maize Stalkborer, Busseola fusca

Busseola fusca affects maize, sorghum and sugar cane, damaging both the plant and the flowers

The African maize stalkborer originates from and is present throughout mainland sub-Saharan Africa. It is not known to occur outside this area.This species occurs from sea level to altitudes above 2000 m and has adapted to different local conditions.  Its larvae are the active destroyers of crops in both the flowering and vegetative stages. They attack the stems, leaves and seeds of plants, including wild grasses.

Biology

Adult African maize stalkborer moths lay eggs in a row between the stem and leafsheath. Each female lays on average about 200 eggs over its short lifetime which lasts several days – its exact duration depends on temperature and other factors. Egg laying on maize is usually concentrated on plants that are less than 2 months old with the leaf sheath of the youngest unfolded leaf being the most attractive part of the leaves for females. The eggs hatch in 3-5 days and larvae move into the leaf whorls to feed. When older (third instar), they tunnel into the stems where they feed for 3-5 weeks before pupating within the tunnels that they have produced in the stems. The adult moth will emerge after a pupal period of 7-14 days from a hole that they produced before pupation. Adults mate soon after emergence. Under favourable conditions the life cycle can be completed in 7-8 weeks but during dry and/or cold weather the larvae can enter a period of suspended development (diapause ) of 6 months or more in stems and other plant residues.

Nature of Damage

First-instar larvae feed in the young terminal leaf whorls producing characteristic patterns of small holes and ‘window-panes’ (patches of transparent leaf epidermis) where tissues have been eaten away. Later they eat into the growing points, which may be killed so that the dead central leaves form characteristic dry, withered ‘dead-hearts’. Older larvae tunnel extensively in stems, eating out long frass-filled galleries which may weaken stems and cause breakages. Larvae also tunnel into maize cobs and into the peduncles of sorghum and millet inflorescences and may seriously affect grain production.

Symptoms by affected plant part:

  • Growing points: internal feeding; boring; external feeding; dead heart (central leaves become dry and withered); frass visible.
  • Inflorescence: abnormal colour; internal feeding; Frass visible.
  • Leaves: external feeding; young terminal leaf whorls have patterns of small holes and ‘window panes’ where tissue has been eaten away. Frass visible.
  • Roots: internal feeding.
  • Seeds: frass visible; empty grains.
  • Stems: abnormal growth; internal feeding shown by long frass-filled galleries; dead heart ; visible frass.
  • Whole plant: dead heart ; plant dead; dieback; internal feeding; frass visible.
  • Maize plants are less able to tolerate stem borer attack than sorghum and pearl millet plants and yield losses of 12% or more occur.
Monitoring

Monitoring of Busseola fusca can be done with pheromone lures, as the pest is very difficult to detect in its early stages of development. There is also the potential to apply mating disruption techniques to pest management. Please enquire with Russell IPM for the latest pheromone lure formulation developed to monitor the African maize borer.

In addition, traps are available for lure application.

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