Potential Biopesticides from Seed Extracts: A Sustainable Way to Protect Cotton Crops from Bollworm Damage

In the current study, the inhibitory effect of extracts from Gramineae (wheat, barley, and corn) and Leguminosae (sophora, bean, and pea) seeds was studied on the digestive alpha-amylase activity in cotton bollworm (Helicoverpa armigera Hubner). The insect was bred on artificial food based on Vigna unguiculata in the greenhouse condition (26 ± 2 °C, 60 ± 10% (Relative Humidity), R.H., 16:8 (Light: Darkness), L: D). The extracts of wheat (95.2%), barley (84.6%), corn (73.8%), sophora (77%), Vigna unguiculata (52%), and pea (56.7%) significantly inhibited the alpha-amylase activity in H. armigera. Studying the impact of different fractions (obtained via deposition at various concentrations of ammonium sulfate salt) on the alpha-amylase enzyme activity demonstrated that in 0–30% fractions, wheat, barley, and sophora have the highest effect (95.26%, 94.65%, and 94.73%, respectively) compared to the other fractions. The inhibitory activities of 0–30% fractions of corn, bean, and pea were 83.3, 56.94, and 50.92%, respectively. In 30–50% fractions, the most effective ones were those of wheat and barley with the inhibitory activity of 79.7% and 82.9%, respectively. In addition, bean and pea fractions inhibited 25.2% and 27.5%, in that order. No significant inhibitory impact was detected in 50–70% or higher fractions. The investigation of the impact of pH values (i.e., 2, 4, 8, and 10) on the inhibition of the alpha-amylase enzyme activity introduced 8–10 as the optimum pH in H. armigera. Nanotechnology offers several ways to enhance plant-based pesticides, which are a solution for making plant extract usage more efficient. The exploration of plant-based pesticides, in conjunction with the incorporation of nanotechnology and other scientific fields, offers a wide range of prospects for further investigation.