No abstract

Plutella xylostella has become particularly notorious for its resistance to various insecticides. The toxicities of abamectin, hexaflumuron and indoxacarb to third instar larvae of the pest were assayed using the leaf-dipping method. The results showed that abamectin and indoxacarb with the lowest LC50 values exhibited stronger toxicity to larvae than hexaflumuron. To determine the synergism of PBO, DEM, DEF and TPP on the toxicity of tested insecticides and demonstrating possible biochemical mechanisms, an abamectin-, a hexaflumuron-and an indoxacarb-resistant strain of P. xylostella were selected under laboratory conditions. After 10 generations of selection, the selected strains developed 14.21, 7.08, and 32.36-fold higher resistance to these insecticides, respectively. Abamectin resistance in abamectin-selected strain was suppressed with the synergists such as DEM and PBO, suggesting the involvement of monooxygeneses and glutathione S-transferase in the development of resistance in P. xylostella. Treatment with PBO and DEF significantly decreased the toxicity of hexaflumuron in the hexaflumuron-selected strain. Also, in indoxacarb-selected strain, the maximum synergism was occurred using PBO and DEF, followed by DEM and TPP. Hexaflumuron and indoxacarb synergism studies indicated in hexaflumuron resistance, monooxygenases and esterases, and in indoxacarb resistance, monooxygenases, esterases and glutathione S-transferae may be involved in the resistance mechanisms

Phthorimaea operculella is a significant insect pest of cultivated potatoes in tropical and subtropical 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 insecticidal 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

Summary Phthorimaea operculella (PTM) is an economically significant invasive potato insect pest in tropical and sub-tropical regions. Due to many problems concerning chemical insecticides, biocontrol agents such as entomopathogenic fungi have attracted researchers’ interest regarding their application as a part of integrated potato tuber moth management strategies in several countries. Hence, in the present study, we examined the lethal effects of entomopathogenic fungus, Metarhizium anisopliae (used as pure culture (PEF) or formulated with MCM-41 silica nanomaterial (MCM-41@fungus)) on eggs and neonate larvae of PTM. The MCM-41was completely characterized by Fourier transform infrared (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDS), X-ray diffraction (XRD), and Thermogravimetric analysis (TGA) techniques. The morphology of MCM-41@fungus was evaluated by scanning electron microscope (SEM). The morphology of the mesoporous structure was exhibited to be homogeneous, regular, and spherical. LC50 values of PEF and MCM-41@fungus were estimated to be 1.7×107 and 2×105 conidia/ml for eggs and 1.8×106 and 1.5×104 conidia/ml for neonate larvae, respectively. Hence, bioassays demonstrated that MCM-41@fungus was more toxic than the pure culture at egg and neonate larval stages of the pest. The results exhibited that pure M. anisopliae and its nano-formulation could play key roles as biopesticides in management programmes of P. operculella.