Influence of salicylic acid on plant defense, growth and biochemical composition of Salix alba infected with Lymantria obfuscata in Kashmir

Lymantria obfuscata poses a significant threat to Salix alba plantations in Kashmir, creating an urgent need for sustainable, non-chemical pest management strategies. The present study aimed to evaluate the efficacy of salicylic acid (SA) as a plant defense inducer against this herbivore. In this experiment, Salix alba cuttings were subjected to three concentrations of SA (2, 3, and 4 mM) using spray and dip application methods prior to infestation with L. obfuscata larvae. Our results indicate that salicylic acid significantly reduced leaf defoliation in a dose-dependent manner; specifically, the dip method with 4 mM SA exhibited the lowest defoliation (13.10%) compared to 25.20% in control groups. SA treatment significantly suppressed larval and adult growth, with larvae feeding on 4 mM SA-treated dipped cuttings exhibiting an average weight of 2.82 mg versus 3.92 mg in the control treatment. Furthermore, salicylic acid treatment had a significantly positive impact on vegetative growth, enhancing leaf area (14.25 vs. 10.50 cm2 in control), plant height (37.20 vs. 30.80 cm), and root length (15.25 vs. 12.37 cm). Quantification of defensive metabolites revealed that the treatment significantly increased total phenol, total flavonoid, and total tannin content in SA-treated plants. GC-MS analysis confirmed that SA-treated plants accumulated higher endogenous SA levels, particularly in dipped plants (1.00 mg/g DW), compared to controls (0.10 mg/g DW). In conclusion, the application of 4 mM SA via the dip method effectively bolsters the morphological and biochemical defense mechanisms of Salix alba, offering a potent and sustainable strategy for managing Lymantria obfuscata infestations.