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Intraspecific Competition in Sitophilus oryzae (L.) and Sitotroga cerealella (Oliv.) in Grain Sorghum

  • M. E. Hassan Shazali (a1)

Abstract

Intraspecific competition in the rice weevil, Sitophilus oryzae (L.) and the angoumois grain moth, Sitotroga cerealella (Oliv.) in grain sorghum was studied in laboratory experiments. Progeny production per female of each of the two species when reared separately, decreased as the initial parent population density increased. The number of progeny produced by Sitophilus oryzae increased to a peak, and then declined sharply with a further increase in initial parent population density, characteristic of a scramble competition. In contrast, the progeny produced by Sitotroga cerealella increased with an increase in parental density to reach a fairly constant maximum (flat topped curve), characteristic of a contest competition. It is concluded that intraspecific competition will not limit the potential of the grain moth S. cerealella of becoming a major pest of stored sorghum.

La compétition intraspécifique au sein de populations du charançon du riz, Sitophilus oryzae (L.) et de l'alucite des céréales, Sitotroga cerealella (Oliv.) a été étudiée dans des conditions de laboratoire. En élévages separés, la prolificité par femelle de chaque espèce diminuait au fur et a mesuré que la densité de la population parentale initiale augmentait. Le nombre de progénitures de Sitophilus oryzae augmentait jusqu'à un pic, pour ensuite chuter abruptement suite a l'augmentation de la population parentale, un fait caractéristique a une compétition ascendante. Par contre, le nombre de progénitures chez Sitotroga cerealella croissait en même temps que l'augmentation de la densité de la population parentale mais pour atteindre un maximum constant (courbe à un sommet aplani), caractéristique devolue à une compétition concurrente. On a donc conclu que la compétition intraspecifique ne pourra pas limiter la potentialité de S. cerealella, d'infliger des dégâts importants au sorgho emmagasiné.

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Intraspecific Competition in Sitophilus oryzae (L.) and Sitotroga cerealella (Oliv.) in Grain Sorghum

  • M. E. Hassan Shazali (a1)

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