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Plantwise Factsheets for Farmers

Osama destroys maize


Recognize the problem

Osama is also known as larger grain borer, scania or dumusi. Osama can ruin all of the food in a store. Osama is a dark brown beetle, with two body parts. The head is round and the stomach is rectangular, unlike the maize weevil, also known as nondo. The weevil is black and has a pointed mouth.


Osama attacks maize right from the field and continues in the store. It also feeds on wood, plastics, storage bags and cassava. Osama bores into the grain, and feeds, leaving an empty shell, while the weevil only feeds on the heart of the grain. Osama also lives in the granary, especially in old maize, and is ready to attack as soon as you put your maize in the store.


  • Harvest early, before Osama has a chance to get into the grain. Harvest maize as soon as the black layer has formed between the tip of the maize grain and the cob.
  • Shell and dry it until it is very dry. The maize must be so dry that when you bite it, it is hard to break. Dry maize is harder for Osama to enter.
  • Clean your store thoroughly. Then dust or spray your store with insecticide (Actellic Super EC). Use 10 teaspoonfuls of Actellic in 20 litres of water. Follow the instructions on the label. Only buy products in original packages, from recognized shops. This way you will avoid buying fake or expired products.
  • Dust the storage bags before and after filling them. Use a grain dust which is not poisonous to people, such as malathion+permethrin (e.g. Skana Super), spinosad (e.g. Spintor Dust), fenitrothion+fenvalerate (e.g. Sumicombi) or pirimiphos-methyl (e.g. Actellic). Dust the grain thoroughly with 50 grams for a 90 kilo bag. Keep in a well-ventilated store. Use new bags to avoid contamination.

When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.

The recommendations in this factsheet are relevant to: Ghana, Kenya

Authors: J Chesoro, J Wanyama, K Wairimu, M Kamidi, M Wanyonyi, P Kalama, R Onyango, W Kiiya, S Rono, T Mwangi, J Mulati, E Manono, E Lunzalu, A Mugita, E Wanyama, P Wang'unda, T Lobeta

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