Insecticidal effect of photorhabdus temperata subsp. thracensis derived-secondary metabolites against three stored product pests

Abstract

This study evaluates the insecticidal potential of secondary metabolites derived from Photorhabdus temperata subsp. thracensis, symbiotically associated with the entomopathogenic nematode Heterorhabditis bacteriophora HBH hybrid strain, against three major stored-product insect pests: Tribolium confusum, Rhyzopertha dominica, and Sitophilus oryzae. The cell-free bacterial culture supernatant was topically applied to adult insects under laboratory conditions, and the mortality was recorded over a 5-day period. Results indicated significant speciesspecific variation in susceptibility. R. dominica exhibited the highest mortality (96.7 % by day 5), followed by T. confusum (70.0 %) and S. oryzae (53.3 %). The observed effects were time-dependent, with mortality rate increasing progressively over the exposure period. The findings suggest that P. temperata subsp. thracensis secondary metabolites have promising bioinsecticidal properties against stored-product pests and could serve as an eco-friendly alternative to synthetic insecticides. Further research is needed to characterize the active compounds and optimize delivery methods under storage conditions.