Evaluation of Physical Losses of Three Wheat Varieties Caused by Rhyzopertha Dominica (f.) (coleoptera: Bostrichidae)

Rhyzopertha dominica (F) is primary pest of stored cereals especially wheat under tropical conditions. The extent of physical damages caused by R. dominica to three common Pakistani wheat varieties was studied. The varieties involved were Sehar -2006, Inqalab-91 and Shafaq. There was recorded significant production of frass material and weight loss in all tested varieties after pest infestation, adversely affecting the quantity of wheat. There was also recorded significant increase in population of R. dominica in the inoculated substrates. The highest level of cereal degradation was recorded for Inqalab-91 followed by Sehar-2006 and Shafaq. It is suggested that Shafaq could be used for long term storage purposes and breeding programs due to its relative resistance against R. dominica. The results of present studies are likely to be helpful for stake holders and go downs owners in making effective management decisions to control R. dominica thus contributing in sustainable wheat supply. Introduction The world's most widely cultivated cereal crop is Wheat, Triticum aestivum L. (Family: Gramineae) (Kumar et al., 2011). It is staple food for human beings worldwide, because it has high nutritional value (Waiss et al., 1987). Pakistan is an agricultural country and wheat (Triticum aestivum L.) is the major agricultural commodity. It contributes 3.0 percent to GDP and grown over wide area of the country (NARC, 2011). Most of the wheat produced has to be stored for future use because it is cultivated for only a short period of the year. Stored wheat undergoes severe damages due to living and nonenvironmental factors (Kent & Evers, 1993). Insect pests are the major constraint among living factors causing significant physical and biochemical losses to stored grains (Madrid et al., 1990; Hussain et al., 1996; Khan et al., 2010). About 10 to 20% losses are reported in Pakistan by more or less than 23 insect species. Among these, Rhizopertha dominica, Sitotroga cerealella, Tribolium castaneum and Sitophilus spp. are most abundant (Khan et al., 2010). These insects attack on stored wheat in a coordinate manner and cause significant reduction in weight. The lesser grain borer, Rhyzopertha dominica (Coleoptera: Bostrichidae) is highly destructive cosmopolitan pest of stored wheat (Haines, 1991). R. dominica can tolerate a wide range of environmental conditions. Its growth rate reached up to 20 times per month under optimum conditions (34°C and 70% relative humidity). It is internal feeding pest that leave the wheat kernels as hollow husks deteriorating their quality and quantity. Besides these, it makes the stored commodity susceptible to attack of other pests and can invade in other stored cereals of nearby location (FGIS, 1997). Due to its notorious nature R. dominica has been under study by many scientists. Jood and Kapoor (1992) investigated the effects of R. dominica using different cereals and recorded significantly decreased protein and starch digestibility. Some scientists reported deterioration of organoleptic characteristics of infested wheat (Jood et al. 1993). There are also reports on significant depletion of total lipids, phospholipids and galactolipids while uric acid increased significantly (Jood et al., 1996). Sayed et al. (2006) recorded significant reduction in weight of wheat grains after infestation with R. dominica. Perusal of literature revealed that R. dominica should preferably controlled to avoid quantity and thus capital losses by stake holders. None of the control strategies would be cost effective if the extent of losses is not known so present investigation was carried out to determine frass material, weight loss and population increase of R. dominica in three verities of wheat viz., Sehar-2006, Inqalab-91 and Shafaq under storage conditions.