Larger grain borer

Preferred Scientific Name: Prostephanus truncatus

Larger grain borer (Prostephanus truncatus) is a beetle that was introduced separately into east and west Africa, but by the mid 90's was widespread across 11 African countries.

Read more Down

Why is it a problem?

The larger grain borer is known to cause maize yield losses of US$91 million per annum in Tanzania and cassava yield losses of US$800 million per annum in West Africa. Farmers have also found that if they grow cassava in areas which are infested with the borer, they are not allowed to export their harvest.


  • Severe losses to staple food crops
  • Limits exportation of crops
  • Reduces native biodiversity
  • Negatively impacts livelihoods

What’s the solution?

Chemical control 

The most effective method of controlling larger grain borer is the use of synthetic pyrethroid insecticides such as permethrin and deltamethrin. However, these insecticides have proved to be ineffective against other storage pests, such as Sitophilus spp, which are found in the same pest complex as the invasive beetle. These other pests have proven more susceptible to organophosphorus pesticides. A combination of these and the synthetic pyrethroid insecticides provide an effective method for protecting farm-stored grain from pests, as long as high quantities are applied relatively frequently. 

Biological control

The predator Teretrius nigrescens has been indicated as a biocontrol solution to the larger grain borer. However, despite becoming quickly and easily established across large parts of Africa, it has not reduced the density of the pest by enough for it to be considered a biocontrol agent.

However, it does meet the impact criteria to be considered an important part of the integrated pest management system for dealing with the beetle. 

Fact file

Name Larger grain borer



For more information on distribution, view the full datasheet available here


Maize growing regions

Natural enemies

Teretriosoma nigrescens has been shown to protect maize crops from the larger grain borer


A threat where maize is grown and stored

Likelihood of entry

Now present in all maize growing regions



Further reading

Visit our online resource of research and full text articles and journals
Invasive Species Compendium

More invasive species

More Species