The Susceptibility of Some Date Cultivars to the Infestation by the Saw-Toothed Grain Beetle, Oryzaephilus surinamensis L. (Coleoptera-Silvanidae)

Abstract

The objective of this study was to investigate the susceptibility of four date cultivars to the attack of the saw toothed grain beetle Oryzaephilus surinamensis (L) which is a very important store pest in Sudan. The four dates cultivars were, Barakawi, Gondeila, Bentamoda, and Gaw. The latter cultivar is locally propagated from seeds. The date fruits of these four cultivars were harvested and brought from Tangasi horticultural gardens in the Northern state in season 2003. The study was conducted during the period early December 2003, to mid January 2004. a total period of 6 weeks. The study was carried out in a date store at Omdurman date market. The larvae and adults of the pest inflict variable degrees of damage which may reach a heavy a stage when the pest feeds on fruit content and changes it to a powder made-up mostly of faeces. Even a minor damage reduces the quality and marketability of the dates due to the presence of adults, pupae, larvae and insect faeces mixed with dates . The degree of damage is evaluated weekly in a well designed experiment. The results showed that Barakawi was the most resistant cultivar against the beetle where the infestation reached only a mean of 18.4%, Gaw showed 27.9%, Bentamada 35.6% and the least resistant cultivar was Gondeila where the recorded infestation reached 40%. The effect of the presence of the fruit cap (perianth) on the degree of the infestation of the fruits was studied. The result showed clearly that the higher the percentage of the fruit retaining their caps, the lower the percentage of the infestation and vice versa. The mean percentage of infestation among the fruits that lost their caps was 47.3% while the infestation percentage among the dates that retained their caps was 15.4%. This indicates that the damage of this pest could be significantly reduced by careful harvesting and handling of the dates.