Abstract
Ten strains of Tribolium castaneum, six strains of Tribolium confusum and 13 strains of Sitophilus zeamais from Malawi were tested for susceptibility to y-BHC (lindane) and malathion. The strains were collected from maize cribs in different parts of the country with the exception of two strains of Sitophilus zeamais which were collected from imported packages of seed maize. Resistance to y-BHC was found in six strains of Tribolium caslaneum while three of these strains were also partly resistant to malathion. It has been concluded that resistance genes in Tribolium castaneum remain easily integrated in the genome of unselected populations. The strains of Tribolium confusum and Sitophilus zeamais were susceptible with the exception of the strains of Sitophilus zeamais from imported seed maize which proved to be highly resistant to y-BHC. A critical situation has not yet been reached in Malawi. However, it seems likely that alternative pest control methods for the protection of stored produce at the small farms are required in the near future.
