Diapause induction and termination in Indian strains of Trichogramma chilonis (Hymenoptera: Trichogrammatidae)

Abstract

AbstractThe role of temperature in diapause induction was studied as a mode of long-term storage of Trichogramma chilonis (Ishii) (Hymenoptera: Trichogrammatidae). Three different strains of this widely used biocontrol agent (T. chilonis Nilgiris strain, T. chilonis Kodaikanal strain, and T. chilonis 15 °C strain) reared on the factitious host Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) were used for this experiment. Except T. chilonis laboratory strain, all the other strains could successfully undergo diapause at their pre-pupal stage. Maximum percentage of healthy pre-pupae were recorded in the three strains by providing a pre-storage temperature of 10 °C for 35 days with eight hours of photophase wherein 75–87% could enter into diapause. Further, at a maintenance temperature of 5 °C with 24 hours of scotophase, diapause could be maintained. Diapause could be terminated after six months of storage with 23–36% of adult emergence. However, there was significant reduction in longevity and parasitism rate of the emerged adults. Considering superior biological parameters, 95 days of storage (including pre-storage duration) could provide around 60% adult emergence. Successful long-term storage of T. chilonis strains through diapause induction can facilitate commercial insectaries in stockpiling this biocontrol agent for large-scale field releases. This is the first study on successful induction and termination of diapause in T. chilonis strains and evaluating their performance attributes.