Phosphine Resistance during different Developmental stages of Trogoderma granarium Everts

The relative tolerance of different developmental stages of susceptible and phosphine-resistant strains of Trogoderma granarium (Everts) to phosphine is reported. Eggs showed a successive significant decrease, while the larvae showed a successive increase in ttlerance eo phosphine with age. Among the different developmental stages of the susceptible strain, 1 d old eggs were the most tolerant and the first-instar larvae were the most susceptible. In the resistant strain, the fifth-instar larvae were the most tolerant followed by 1 d old eggs. Phosphine-resistant strain of T. granarium manifested variable degree of resistance to phosphine during different ntvelopmental stages.