Abstract
Khapra beetle, Trogoderma granarium is one of the most notorious pests of stored grains. This study was aimed to evaluate the toxicity of phosphine to 4th, 6th instar larvae and adult beetle in phosphine resistant populations viz., Gujranwala, Mandi Bahauddin-I (M.B.Din-I), Mandi Bahauddin-II (M.B.Din-II),Gujrat and Sargodha and a susceptible
population of T. granarium. The 4th, 6th instar larvae and adult beetles of T. granariumwere exposed to different sub lethal concentrations of phosphine for 20 hours. Based on LC50 data, Gujranwala population was found to be most resistant to phosphine whereas Sargodha population was found the least resistant population. Gujranwala population required 113.5, 128.8 and 168.1% more phosphine concentration in 4th, 6th instar larvae and adult beetles, respectively with reference to susceptible population of T. granarium.The various insect populations based on LC50 of phosphine is graded as Gujranwala ˃ MBDin-I ˃ Gujrat ˃ MBDin-II ˃ Sargodha ˃ control.The LC50 values of
phosphine against adult were always less than of 6th instar larvae and likewise LC50 of phosphine against 6th instar larvae is always less compared to 4th instar larvae in all populations. The 4th instar of Gujranwala required 17.03 and 25.39% more phosphine than 6
th instar larvae and adult beetle, respectively. Based on LC50 data, gradation followed by developmental stages is 4th instar ˃ 6
th instar ˃ adult. Adult insects seemed to be more sensitive to phosphine
compared to 6th and 4th instar larvae.
Tanzeela Riaz, Farah Rauf Shakoori, Syed Shahid Ali. (2016) Toxicity of phosphine against tolerant and susceptible populations of Trogoderma granarium collected from Punjab, Pakistan, Punjab University Journal of Zoology, Volume 31, Issue 1.
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