Suitability of Tamarind and Some Selected Crop Seeds for the Survival and Development of Sitophilus Linearis (Herbst) (Coleoptera: Cucurlionidae)

Sitophilus oryzae (L.), Sitophilus zeamais (Mots.) and Sitophilus granarius (L.) are major pests of stored grain, especially on cereals. Sitophilus linearis (Herbst) a congeneric of the afore-listed species was obtained from seeds of a wild plant, Tamarindus indica L. The development of S. linearis on some selected crop seeds as well as tamarind seeds was investigated in the laboratory at 25.3-30.3 [degree]C and 75.0% [plus or minus] 5.0 RH. One hundred grammes each of heat sterilized maize, rice, sorghum, millet, cowpea and tamarind seeds were infested with 100 unsexed adults of S. linearis and observed to determine the suitability of the different substrates for the development of the weevil. Sitophilus linearis bred and multiplied on the tamarind seeds but not on the selected crop seeds in the laboratory. Mean developmental period on the tamarind seeds was 32 days. The highest number (51) of adults that emerged on the first day of emergence was from cultures set up with one-week old adult insects. The highest mean weight (3.9mg) was also recorded on the cultures set up with one-week old insects. However, both mean number of emerged adults and mean adult weight were not significantly different (P>0.05). A significant difference was recorded in the mean percentage survival period of S. linearis on the different substrates (P<0.05) with the longest survival recorded on tamarind seeds. It can therefore be concluded that Sitophilus linearis, though a member of the family of grain weevils, could not reproduce on the cereal substrates or the cowpea seeds presented to it in the laboratory. If further studies confirm these findings, then Sitophilus linearis may pose no threat to cereal production due to its inability to survive and reproduce on them.