Efficacy of Diatomaceous Earth and Deltamethrin Alone and in Combinations on Mortality and Energy Reserves of Insecticide Resistant Strains of Stored Grain Pest, Trogoderma granarium

ABSTRACT The present study was conducted to determine the LC50 of deltamethrin and diatomaceous earth (DE) alone and in different combinations i.e., 0.5:01, 01:0.5 and 1:1 against 4th instars of insecticide resistant populations of Trogoderma granarium collected from godowns of Gujranwala (GUW), D.G. khan (DGK), Okara (OKR), Lahore (LAB-S) and Layyah. The LC50 values of deltamethrin against 4th instar larvae of GUW, DGK, OKR, Layyah and LAB-S were 514, 353, 303, 189 and 98 ppm respectively while for the DE these values were 3606, 2684, 2407, 2192 and 2065 ppm, respectively. Based on the values of LC50 deltamethrin was found to be more effective than DE. Among the tested populations, GUW population was most resistant while LAB-S population was least resistant. Efficacy of deltamethrin and DE in various combinations was also tested against the same larval stage of different strains of pest populations and the mixture 0.5DM+1DE was found to be most effective among all mixtures on the basis of LC50 values and relative toxic unit. The toxicity of this mixture was analyzed on glucose, glycogen, trehalose, total proteins, soluble proteins, free amino acids and total lipids contents of 4th instars larva of most resistant GUW and least resistant LAB-S populations at exposure to LC20. Among the biochemical parameters glucose, soluble proteins and FAA contents were found to be elevated significantly whereas the concentration of total proteins, glycogen, trehalose and total lipids was found to be decreased in both populations. Depletion of energy reserves is most probably the cause of mortality of the pest.