Evaluation of entomopathogenic nematodes against whitegrub, Maladera insanabilis Brenske

Abstract

The whitegrubs or rootgrubs including Maladera insanabilis, are the phytophagous immature stages of scarabs, causing heavy economic losses to many field and plantation crops. Out of six entomopathogenic nematode species/strains: Steinernema feltiae, Steinernema species, Ecomax strain, Heterorhabditis bacteriophora, Steinernema glaseri, field collected (JFC) local isolate and Heterorhabditis species Ecomax strain, H. bacteriophora was found to be more virulent against the third instar grubs of M. insanabilis. When hosts were exposed to H. bacteriophora infective juveniles (Ijs) in soil, lower inoculation doses were necessary to kill the host (LD₅₀, 14 090 IJs/100 g soil/grub), the IJs invaded the host at a faster rate (LexT₅₀, 18.38 h), host mortality occurred earlier (LT₅₀, 5.65 days) and more IJs were produced per cadaver of infected host (69 840/grub; 607.30 IJ/mg host body weight), as compared to other tested nematodes.

Keywords:

• roundworms
• Scarabaceae
• exposure time
• dose – mortality
• inoculation