Mass Propagation of Two Entomopathogenic Nematode Species on Different Larval Species in Relation to The Resultant Yield of Nematode Juveniles

The 5^th instar larvae of each of the four insect species were assayed about their capability to play as host for mass propagation of juveniles of two beneficial entomopathogenic nematodes (EPN) species; Heterorabditis bacteriophora and Steinernema carpocapsae in the laboratory at 25 ˚C and 65±5 % R.H.  After exposure of larvae at the rate of 1000 IJs/ 5 larvae, daily microscope inspections were carried out until larval mortality and penetration of the new IJs out from the host larvae. Counts of the newly emerged juveniles were carried out periodically and successively (3, 6, 9, 12, 15, 20, 25 and 30 days after starting emergence). Larvae of Galleria mellonella manifested the shortest period from exposure to IJs until larval mortality (2 days), as opposed to 2.33 days in the case of Spodoptera frugiperda, 2.33 and 3 days after infection of Spodoptera littoralis larvae by H. bacteriophora and S. carpocapsae IJs, respectively, and 4.33 and 2.33 days, respectively for T. molitor larvae indicating the longest period after infection to mortality.
               As for the period from the time of exposure until starting of IJs emergence, that was the shortest (7 days) in the case of S. frugiperda infected by either of the two EPN species and G. mellonella (by S. carpocapsae), while this period was the longest for T. molitor infested by H. bacteriophora and S. carpocapsae  ( 12 and 14 days, respectively). After 30 days of starting emergence out of host larvae, the highest mean of the total number of H. bacteriophora juveniles (364767 IJs) resulted from T. molitor larvae, followed by 284680 IJs/ S. frugiperda larvae and 259817 IJs from G. mellonella larvae. While, in the case of S. carpocapsae; the highest number of harvested juveniles (341790 IJs) was produced from G. mellonella larvae, followed by 258363 IJs/ a S. frugiperda larvae and 246633 IJs/ a S. littoralis larvae.
             As a general conclusion, for mass – propagation of H. bacteriophora, rearing on T. molitor larvae is recommended, followed by G. mellonella. On the same target for S. carpocapsae; to obtain the highest production of juveniles, rearing on G. mellonella larvae is the best followed by S. littoralis, then S. frugiperda larvae.