الفهرس 
Population density for storage insects
Susceptibility and preferabilityOnly 14 pages are availabe for public view
 |  | from | 99 |  |  |
| | | from | 99 | | |
Abstract
Maize, Zea mays L., is the second most produced cereal after wheat in the world. It is cosmopolitan in distribution and widely consumed by man and his animals (Makate, 2010). About 50 maize species exist and grains vary in colour, texture, shape and size. Maize grains are rich in Vitamins A, C and E, carbohydrates, essential minerals and protein. World wide production of maize in 2011 was 883,460,240 tonnes with the largest producer, the United States, producing 35.5%. Africa produces 7.4% and the second largest African producer (after South Africa) was Nigeria with 9,180,270 tonnes (FAO, 2013).
During postharvest storage, maize grains are vulnerable to many insects. Among those, Angoumois grain moth Sitotroga cerealella (Olivier), lesser grain borer, Rhyzopertha dominica (F.), weevils complex Sitophlilus spp., Khapra beetle, Trogoderma granarium Everts and red flour beetle, Tribolium castaneum (Herbst) are very important (Lohar et al., 1997; Ebeling, 2002). But most damage is done during storage. Damaged grains have reduced nutritional values, low percent germination and reduced weight and market values, respectively. World wide seed losses ranging from 20 to 90% have been reported for untreated maize due to the maize weevil Sitophilus zemais (Giga et al., 1991).
The rice weevil, Sitophilus oryzae (L.), is a cosmopolitan pest which is considered to be one of the most destructive species in stored grain. It is classified as a primary pest, which can easily infest sound seeds, enabling other species (the secondary pests), which are not capable of breeding on intact grains, to cause additional damage (Hill, 1990; Rees, 1995).Since its larvae develop in the internal part of the kernels, the infestation is not visible at the first stages Moreover, S. oryzae has developed a considerable level of resistance, to many traditional residual protectants (Arthur, For instance, the rice weevil is considered to be one of the most resistant stored-product insect species to pyrethroids, and usually cannot be controlled by application rates that are effective against most other stored-grain beetle species (Samson and Parker, 1989; Arthur, 1992, 1994, .These issues highlight the need for assessing other substances that can be effective against this pest.