Influence of protein composition in artificial solid media on production and activation of entomopathogenic nematode, Steinernema siamkayai

ABSTRACT Steinernema siamkayai is an indigenous entomopathogenic nematode (EPN) with strong potential for biological control in tropical agriculture. However, its wider application in Thailand is constrained by limited production efficiency. This study evaluated artificial solid media differing in protein composition to determine their effects on infective juvenile (IJ) recovery, activation, and biological performance under in vitro conditions. Four lipid – agar – based media were formulated by progressively replacing nutrient broth with fresh beef liver. Media containing low levels of beef liver (0.5–1.0% w/v) supported high IJ yields and survival rates exceeding 99%, comparable to those obtained with the standard lipid – agar medium. Beef liver supplementation significantly shortened IJ recovery time and enhanced activation to the adult stage, despite the absence of pre-inoculated symbiotic bacteria, indicating that appropriate nutrient composition alone can sustain functional nematode – bacteria interactions. In laboratory filter paper bioassays, IJs reared on the modified media achieved >96% mortality in both Galleria mellonella and Spodoptera exigua larvae at a dose of 100 IJs per larva, results comparable to those obtained using insect-derived IJs. These findings demonstrate that protein source composition is a key determinant of IJ production and performance and highlight the potential of simplified solid media for efficient in vitro production of S. siamkayai.