Nanotechnology is increasingly being used in areas of pesticide production and pest management. This study reports the isolation and virulence of a new Metarhizium anisopliae isolate SM036, along with the synthesis and characterization of M. anisopliae–chitosan nanoparticles followed by studies on the efficacy of nanoparticles against Plutella xylostella. The newly identified strain proved pathogenic to P. xylostella under laboratory conditions. The characterization of M. anisopliae–chitosan nanoparticles through different analytical techniques showed the successful synthesis of nanoparticles. SEM and HRTEM images confirmed the synthesis of spherical-shaped nanoparticles; X-ray diffractogram showed strong peaks between 2θ values of 16–30°; and atomic force microscopy (AFM) analysis revealed a particle size of 75.83 nm for M. anisopliae–chitosan nanoparticles, respectively. The bioassay studies demonstrated that different concentrations of M. anisopliae–chitosan nanoparticles were highly effective against second instar P. xylostella under laboratory and semi-field conditions. These findings suggest that M. anisopliae–chitosan nanoparticles can potentially be used in biorational P. xylostella management programs.

Megalurothrips usitatus (Bagnall) is one of the most harmful pests of leguminous plants. In order to expand our knowledge on the infection of M. usitatus by entomopathogenic fungi, two newly identified isolates of Akanthomyces attenuatus (Zare & Gams) were tested for their pathogenicity against M. usitatus. Both isolates of A. attenuatus (SCAUDCL-38 and SCAUDCL-56) were isolated from soil and were identified by morphological and molecular analyses. The adult females of M. usitatus were treated with five different concentrations (1 × 10⁴, 1 × 10⁵, 1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ conidia/mL) of the isolates. Our results revealed 76.25% and 57.5% mortality of M. usitatus after five days of treatment with 1 × 10⁸ conidia/mL of SCAUDCL-38 and SCAUDCL-56, respectively. The median lethal concentrations (LC₅₀) of SCAUDCL-38 and SCAUDCL-56 calculated through linear regression analysis after five days of fungal treatment of M. usitatus were 1.9 × 10⁶ and 1.5 × 10⁷ conidia/mL, respectively, whereas the median lethal time (LT₅₀) observed for 1 × 10⁸ conidia/mL of SCAUDCL-38 and SCAUDCL-56 were 3.52 days and 4.9 days, respectively. A. attenuatus isolates SCAUDCL-38 and SCAUDCL-56 are highly pathogenic strains of M. usitatus. These findings offer valuable information on the development and commercialization of alternative control measures against M. usitatus.

The excessive use of synthetic chemicals for Megalurothrips usitatus (Bagrall) management has resulted in the development of insecticide resistance as well as adverse effects to the natural ecosystem. This has driven the need to develop alternative pest control strategies. This study reports a synergistic interaction between the entomopathogenic fungus Akanthomyces attenuatus (Zare & Gams) and the botanical insecticide matrine against M. usitatus. The results revealed that the germination rate and colony growth of A. attenuatus were inhibited by higher matrine concentrations. Percentage mortalities of M. usitatus following application of A. attenuatus and matrine showed a dose mortality effect. After five days of treatment, all concentrations of matrine combined with different concentrations of A. attenuatus, except one combination (matrine 0.25 mg/mL + 1 × 10⁷ conidia/mL), showed synergistic effect. The activities of acetylcholinesterase and antioxidant enzymes (superoxide dismutase, catalase and peroxidase) in M. usitatus, in response to individual or combined application of A. attenuatus and matrine at the end of the experimental period, were significantly lower than controls. The findings confirm the synergistic action of A. attenuatus and matrine against M. usitatus along with the biochemical phenomenon possibly regulating the synergistic effect.

Cordyceps fumosorosea, an insect pathogenic fungus, produces different toxins/secondary metabolites which can act as pest control agents. This study reports the extraction and characterization of crude mycelial extracts of C. fumosorosea isolate SP502 along with their bio-efficacy against Bemisia tabaci and Aphis craccivora. Fourier transform infrared spectroscopy, liquid chromatography, mass spectrometery and nuclear magnetic resonance analysis of C. fumosorosea isolate SP502 extracts showed the presence of five major compounds—Trichodermin, 5-Methylmellein, Brevianamide F, Enniatin and Beauvericin—which all may potentially be involved in insecticidal activity. The HPLC analysis of C. fumosorosea mycelial extracts and Beauvericin standard showed similar chromatographic peaks, with the content of Beauvericin in the crude toxin being calculated as 0.66 mg/ml. The median lethal concentrations of C. fumosorosea mycelial extracts towards first, second, third and fourth instar nymphs of A. craccivora were 46.35, 54.55, 68.94, and 81.92 µg/mL, respectively. The median lethal concentrations of C. fumosorosea mycelial extracts towards first, second, third and fourth instar nymphs of B. tabaci were 62.67, 72.84, 77.40, and 94.40 µg/mL, respectively. Our results demonstrate that bioactive compounds produced by C. fumosorosea isolate SP502 have insecticidal properties and could, therefore, be developed into biopesticides for the management of B. tabaci and A. craccivora.

Genes of the cytochrome P450 (CYP450) superfamily are known to be involved in the evolution of insecticide resistance. In this study, the transcriptomes of two Megalurothrips usitatus Bagnall (Thysanoptera: Thripidae) strains (resistant and susceptible) were screened for detoxification genes. MusiDN2722 encodes a protein composed of 504 amino acid residues with a relative molecular mass of 57.3 kDa. Multiple sequence alignment and phylogenetic analysis showed that MusiDN2722 is a member of the CYP450 family and has characteristics of the conserved CYP6 domain shared by typical CYP450 family members. RT-qPCR (real-time quantitative polymerase chain reaction) analysis showed that MusiDN2722 was upregulated in the acetamiprid-resistant strain compared with the susceptible strain (p < 0.05), and the relative expression level was significantly higher at 48 h after exposure than at 24 h after exposure. The interference efficiency of the injection method was higher than that of the membrane-feeding method. Silencing of MusiDN2722 through RNA interference significantly increased the sensitivity of M. usitatus to acetamiprid. Overall, this study revealed that MusiDN2722 plays a crucial role in the resistance of M. usitatus to acetamiprid. The findings will not only advance our understanding of the role of P450s in insecticide resistance but also provide a potential target for the sustainable control of destructive pests such as thrips.