Two rates ( 5 & 10 ppm a.i. ) of chlorpyrifos-methyl were applied to wheat grains, stored in tightly-closed glass jars ( each 5 L capacity ) under the laboratory conditions for 12 months . Insecticide residues and its insecticidal activities were evaluated at different intervals. The results showed that, the percent losses in chlorpyrifos-methyl after 12 months were 52.81 % and 59.11 % for the lower and higher rates, respectively, without any insecticidal activity to the insects : Trogoderma granarium and Tribolium confusum . The degradation pattern of the insecticide was triphase with t 0.5 = 34 weeks.

Abstract

Trapping of Rodent pests ; with different types of traps and baits, was conducted in four locations inside and outside the city of Riyadh . Four species of rodents belonging to the families Muridae and Cricetidae were recorded . Rattus rattus was the dominant species in the indoor and Meriones libycus , Mus musculus , and Acomys dimidiatus were in the out door locations . Types of bait and position and orientation of traps affected trapping efficiencies .The most attractive baits were semi-dried dates and wheat grains . Snap traps, specially those arranged oppositely in duplicates , proved to be the most efficient . Rodent populations in different locations were not enough to conduct an experiment for the chemical control with rodenticides .