Potential‎ of plant extracts and ‎their elicitor effect on the red sweet pepper ‎‎(Capsicum annuum L.) defence system against Tetranychus urticae (Acari: ‎Tetranychidae) infestation under greenhouse conditions

Abstract

ABSTRACT We investigated the potential of plant extracts (PEs) of Costus speciosus (CS REAq), Tagetes patula (TP LEEtOH70%), and Helichrysum bracteatum (HB LEEtOH70%) against active stages of Tetranychus urticae (Acari: Tetranychidae) infesting red sweet pepper (Capsicum annuum) and on associated mite predators, Phytoseiulus persimilis and Scolothrips longicornis, under greenhouse conditions. Furthermore, the effect of elicitor PE compounds, which could activate the host plant’s defence system against mite infestation, was investigated through biochemical analyses of sweet pepper. Results revealed that all PE treatments significantly reduced populations of T. urticae active stages over those in their corresponding control groups and were as ‎effective as the standard check (abamectin). TP LEEtOH70%, HB LEEtOH70%, and CS REAq achieved the highest reduction rates with efficacy of 96.29%, 95.79%, and 93.36%, respectively, against adult ‎mites.‎ This study clearly demonstrated that PEs were not harmful to both mite predators. All PE treatments showed marked elicitor effects on sweet pepper defence system with elevated photosynthetic pigment, total phenol, and protein levels and enhanced antioxidant enzyme activity and total yield. The reduction efficiency was plant-part and solvent-dependent. Thus, PEs have the potential as a safe alternative to chemical acaricides in pest management of T. urticae on sweet pepper in greenhouses.