Cuminum cyminum methanolic extract – Fe3O4 nanocomposite: A novel and efficient insecticide against the potato tuber moth (Lepidoptera: Gelechiidae) to protect potatoes

Phthorimaea operculella is a significant insect pest of cultivated potatoes in tropical and subtropi- cal regions such as Iran. Since the potato is one of the most valuable sources of human food, non-chemical control of potato pests is essential. Application of medicinal plant extracts is a low-risk alternative method to synthetic chemical insecticides. Hence, the present study was conducted to investigate a potential strategy to improve the insecticidal activity of plant extracts for efficient management of P. operculella . The insecti- cidal efficacy of pure methanolic extract (PME) and Fe 3 O 4 @methanolic extract (FME) of Cuminum cyminum were evaluated against the potato tuber moth under laboratory conditions. The morphological characteristics of Fe 3 O 4 @Cumin were investigated by scanning electron microscope. Magnetic properties of the samples were determined using a vibration sample magnetometer. XRD was used to prove the crystalline structure of Fe 3 O 4 @Cumin. SEM, FTIR, XRD, and VSM analyses confirmed that the methanolic extract was loaded on Fe 3 O 4 . The toxicity of PME and Fe 3 O 4 @Cumin were evaluated on one-day-old eggs and penetration the first instar larvae of P. operculella into potato tubers and leaves. The LC 50 values of Cumin extract and Fe 3 O 4 @ Cumin were 961.07 and 601.48 and 496.84 and 268.82 ppm for penetrating neonate larvae to tubers and leaves, and 874.90 and 595.16 ppm for eggs, respectively. Bioassays revealed that Fe 3 O 4 @Cumin was more toxic than non-formulated Cumin methanolic extract against eggs and neonate larvae of P. operculella . The formulated methanolic extract was significantly more repellent against the pest. Our results suggested that the prepared nanocomposite could be used as a new effective tool for P. operculella management strategies to protect potatoes.