OPTIMIZATION OF REARING PROTOCOL FOR EGG AND LARVAL PARASITOIDS WITH THEIR ASSOCIATED HOSTS AND EVALUATING THE EFFICACY OF BRACON HEBETOR AGAINST FALL ARMYWORM IN MAIZE

ABSTRACT: The Fall Armyworm (FAW), Spodoptera frugiperda, poses a significant threat to maize production in Patuakhali and other regions globally. To mitigate this problem, the present study focused on developing a rearing protocol for two potential biological control agents: the larval parasitoid, Bracon hebetor, and the egg parasitoid, Trichogramma chilonis and the efficacy of Bracon hebetor was carried out in the bio-control laboratory of Entomology department, PSTU during October 2022 to September 2023. Laboratory trials were conducted to evaluate the efficacy of the reared parasitoids against FAW larvae of different instars. The rearing protocols of B. hebetor were established utilizing the associated hosts, Galleria mellonella (wax moth) and Corcyra cephalonica (rice moth), respectively. The rearing protocol development involved optimizing environmental conditions, nutritional requirements, and host rearing methods to ensure large parasitoid populations. Observations on parasitism rates, and FAW population suppression were recorded to assess the effectiveness of the biological control strategy. The results demonstrated the potential for Bracon hebetor as biological control agent against FAW. The highest parasitism was found in 5th instar larvae which was about 96% while the lowest parasitism was found in 3rd instar larvae which was about 33%. In 4th instar mean parasitization was 6.33±1.52 which is about 63%. The parasitism of FAW by B. hebetor ranged from 20-40 % in net cage trial. The length and breadth of 6th instar larva of wax moth were 1.215 ± 0.13cm and 0.371 ± 0.03cm, respectively while the length and breadth of pupa were 2.13 ± 0.14cm and 0.33 ± 0.03cm, respectively. The length and breadth of 5th instar larva of fall armyworm were 3.66 ± 0.23cm and 0.372 ± 0.02cm while the length and breadth of pupa were 1.46 ± 0.05cm and 0.5 ± 0.00cm, respectively. Overall, the protocol development for rearing of larval and egg parasitoids and their efficacy against FAW provide valuable biological control strategies for managing FAW in maize fields and offer a sustainable alternative to chemical pesticides. 

Keywords: Fall Armyworm, Bracon hebetor, Corcyra cephalonica, Galleria mellonella, maize, Trichogramma chilonis