<p>Evaluation the efficiency of salicylic acid and garlic extract as natural stimulants was attempt in this study to control the harmful effects of cotton leafworm (<i>Spodoptera littoralis</i>). Through a series of physiological, biological, and morphological studies using scanning electron microscopy and biochemical effects. Additionally, the study also compared the effects of both natural materials with one of the well-known recommended insecticides (Scorch® (10% EC)) actually used in <i>S. littoralis</i> control. The second instar larvae were used to assess the efficacy of three concentrations of salicylic acid (250, 500, and 1000 ppm) and garlic extract (25%, 50%, and 75%). The findings recorded significant differences between treated and untreated larvae at all stages but at different levels. The second-instar larvae that were treated with 75% garlic extract had the greatest mortality rate (56.57%). Additionally, nutritional indices such as the consumption index (CI), relative growth rate (RGR), and approximate digestibility (AD) showed the lowest values (0.228g g⁻¹day⁻¹, 1.9% and 10.33%, respectively). Also, larvae fed on 75% garlic extract had the longest larval (20 days) and pupal duration (12 days) and the lowest pupal and adult emergence rates (44.44% and 33.33%, respectively), according to development indices. However, larvae treated with 500 ppm salicylic acid had an effect that was comparable to that of the insecticide (Scorch (10% EC)) in physiological and biological studies. A week following treatment, using a scanning electron microscope (SEM), treated and untreated larvae were examined; on observation, all treatments had damaging effects. The larval exterior morphology (cuticle) developed fissures on both the ventral and upper sides, along with abnormalities in the spiracles and shrinking of the larval body. There were also obvious ruptures in the thoracic legs and the anal plate, which are responsible for adhesion to the substrate. Clear structural anomalies in the mouthparts and head capsule were noticed. Likewise, larvae exposed to 500 ppm salicylic acid and 75% garlic extract showed the lowest levels of acetylcholinesterase (8.82 and 8.8, respectively) and amylase activity (17.08 and 14.4, respectively). Between the control and treated larvae (<i>S. littoralis</i>), significant variations in the quantity and dimensions of amplified DNA fragments were seen in the RAPD profiles produced by primers. SA with high concentration (1000 ppm) recorded the highest number of bands (24) compared with control treatment (11), while 75% garlic extract and 500 ppm salicylic acid treatments more close to control treatments. The study’s findings demonstrated the efficacy of 500 ppm salicylic acid and 75% garlic extract as possible natural substances to fight <i>S. littoralis</i>.</p>