Effect of host egg storage on the storage amenability of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae)

Abstract

The mass production of widely used bio-control agent Trichogramma chilonis primarily depends on the constant supply of their host eggs and availability of suitable storage techniques. Experiments were conducted to develop such techniques of three Trichogramma chilonis Ishii strains (viz. Nilgiris, Kodaikanl and lab) on stored and un-stored Corcyra cephalonica eggs. Differential response was noticed when pupal storage was attempted on un-stored host eggs at 5 and 10 °C. At 10 °C (L: D- 8:16, RH-70 ± 10%), T. chilonis Nilgiris strain could retain its developmental arrest for the longest duration (60 days), followed by T. chilonis Kodaikanal (50 days). All the three tested strains showed a reduced storage capacity at 5 °C (L: D- 0:24, RH-70 ± 10%). However, T. chilonis Nilgiris and Kodaikanal strains could be stored for upto 35 days with 60% emergence rate and lab strain for upto 30 days where emerged adults could survive for 3 days. The study revealed that when stored host eggs are used, the parasitized cards (parasitoids in their pupal stage) are amenable for further storage of minimum 30 days at both 5 and 10 °C. To overcome seasonal fluctuation in host availability, stored C. cephalonica eggs can be used to store pupal stages of the three different strains of T. chilonis at 5 °C for a total duration of 50 days (host egg storage: 20 days + pupal T. chilonis storage: 30 days).