Nature of diapause alters the damage potential and insecticide susceptibility in Chilo partellus (Swinhoe)

The stability of host plant resistance to insects, and efficacy of insecticides against the insect pests is influenced by several inherent traits of the target insects in addition to the environmental factors. Spotted stem borer, Chilo partellus (Swinhoe) is a key pest of maize and sorghum. It undergoes both hibernation and aestivation depending upon the prevailing climatic conditions. We studied the host preference and damage potential of this pest in maize and sorghum, and its susceptibility to different insecticides in F₁ progenies of hibernating, aestivating and nondiapausing strains of C. partellus. The larvae from hibernating strain resulted in greater leaf damage and deadhearts, and had greater larval weight and better survival on maize and sorghum than those from the aestivating and nondiapausing strains, although there were a few exceptions. The susceptible maize and sorghum genotypes were highly preferred by the hibernating larvae, while the resistant genotypes were preferred most by the aestivating strain. Maize was least preferred, while sorghum was most preferred by the larvae from hibernating as compared to aestivating and nondiapausing strains of C. partellus. The larvae from aestivating strain were least susceptible to cypermethrin and thiamethoxam, but highly susceptible to deltamethrin and imidacloprid as compared to the other strains. The present studies showed significant differences in preference and damage potential in the host crops, and susceptibility to insecticides in diapausing and nondiapausing strains of C. partellus. Identification of stem borer resistant genotypes of sorghum and maize, and the insecticides with stable efficacy will be useful for integrated management of this pest.