Insecticidal activity of weed plants, Euphorbia prostrata and Chenopodiastrum murale against stored grain insect pest Trogoderma granarium Everts, 1898 (Coleoptera: Dermestidae)

The efficiency of petroleum ether extracts of weed plants, Euphorbia prostrata and Chenopodiastrum murale, for the control of Trogoderma granarium was investigated. The extracts were prepared in petroleum ether using the whole plants. Diet incorporation was used for mortality bioassay and area preference was used for repellency against third instar larvae of T. granarium. The results showed relatively high rate of larval mortality after 6 days with extract concentrations of 10, 20 and 30%. At 30% the corresponding mortality rates induced by E. prostrata and C. murale were 20 and 25%, respectively. Low larval mortalities were obtained for both plant extracts at 10%. Similarly, repellency assay at 30% extracts found the maximum proportion of larvae that moved away from the treated region of the filter paper to be 88 and 87% for E. prostrata and C. murale extracts, respectively. The repellency of both plant extracts had a positive relationship applied dosage but was negatively correlated with exposure time. The lowest mean number of larvae in F-1 generation was found with 30% E. prostrata and C. murale extracts (60 and 53, respectively) as compared to the control (149). Overall the results indicated that the C. murale extract had a higher insecticidal activity against T. granarium than the E. prostrata extract.