Cell-free supernatants from entomopathogenic bacteria as a potential alternative for managing Tetranychus urticae in tomato

Abstract

Tetranychus urticae is a cosmopolitan pest that causes significant yield losses in tomatocrops. Entomopathogenic bacteria of the genera Photorhabdus and Xenorhabdus producediverse secondary metabolites with acaricidal properties. This study aimed to evaluate theacaricidal and deterrent effects of cell-free supernatants (CFSs) of Photorhabdus luminescens,Xenorhabdus szentirmaii and Xenorhabdus doucetiae against T. urticae in tomato.In Petri dishes, each CFS was sprayed onto leaflets infested with females or eggs. Thedeterrent activity was assessed through dual-choice bioassays. Furthermore, the acaricidaleffect of these bacterial metabolites was validated under field conditions over two growingseasons. After 72 h, CFSs of P. luminescens, X. szentirmaii and X. doucetiae caused mortalityrates of 80.7%, 93.5% and 85.0% in laboratory bioassays, respectively. Furthermore,egg viability was significantly reduced. In choice bioassays, the Repellency, Leaf Damageand Oviposition Indices demonstrated greater pest activity on untreated plants than onthose treated with bacterial compounds. In field trials, X. szentirmaii supernatant reacheda 65.4% mortality rate and significantly reduced leaf damage. Secondary metabolites producedby P. luminescens, X. szentirmaii and X. doucetiae exhibited both acaricidal anddeterrent activity against T. urticae, representing a promising tool for the integrated pestmanagement in tomato production.