This study examined the impact of Metarhizium anisopliae (Hypocreales: Clavicipitaceae) conidia on the eggs, larvae, pupae, and adults of Spodoptera frugiperda. The results showed that eggs, larvae, pupae, and adults exhibited mortality rates that were dependent on the dose. An increased amount of conidia (1.5 × 109 conidia/mL) was found to be toxic to larvae, pupae, and adults after 9 days of treatment, resulting in a 100% mortality rate in eggs, 98% in larvae, 76% in pupae, and 85% in adults. A study using earthworms as bioindicators found that after 3 days of exposure, M. anisopliae conidia did not cause any harmful effects on the earthworms. In contrast, the chemical treatment (positive control) resulted in 100% mortality at a concentration of 40 ppm. Histopathological studies showed that earthworm gut tissues treated with fungal conidia did not show significant differences compared with those of the negative control. The gut tissues of earthworms treated with monocrotophos exhibited significant damage, and notable differences were observed in the chemical treatment. The treatments with 70 and 100 µg/mL solutions of Eudrilus eugeniae epidermal mucus showed no fungal growth. An analysis of the enzymes at a biochemical level revealed a decrease in the levels of acetylcholinesterase, α-carboxylesterase, and β-carboxylesterase in S. frugiperda larvae after exposure to fungal conidia. This study found that M. anisopliae is effective against S. frugiperda, highlighting the potential of this entomopathogenic fungus in controlling this agricultural insect pest.

BACKGROUND: Spodoptera frugiperda is an invasive, widespread agricultural pest in China. However, there have been no reports assessing feeding damage on wheat caused by S. frugiperda. To clarify the fitness and potential damage of S. frugiperda to wheat, this study analyzed the population parameters of S. frugiperda fed on wheat in a laboratory and simulated the potential damage in field conditions.
RESULTS: The population parameters of S. frugiperda were compared using life tables on wheat at the seedling and adult plant stages. The adult female longevity of S. frugiperda varied from 12.29 days on seedling plants to 16.60 days on adult plants. Egg production was significantly higher when fed on wheat at the seedling stage (646.34 eggs) than when fed on adult plants (495.86 eggs). On wheat at the seedling and adult plant stages, the mean generation times were 35.42 and 38.34 days, respectively, and the intrinsic rates of increase were 0.15 and 0.14, respectively. Spodoptera frugiperda completed development and increased its population in wheat at both plant growth stages. In the field, the effect of different larval densities on the 1000-kernel weight of wheat was significantly different. An action threshold of 40 larvae per m2 was estimated, and the higher population densities caused a yield loss of 17.7%.
CONCLUSIONS: Spodoptera frugiperda can complete its life cycle on wheat at different stages. Wheat can serve as an alternative host for S. frugiperda. If S. frugiperda reaches 320 larvae per m2 density during wheat growth, it will cause yield loss exceeding 17%. © 2023 Society of Chemical Industry.

Pyrethroid and indoxacarb are commonly used pesticides to control the fall armyworm (Spodoptera frugiperda) in the crops. There are a series of consequences caused by the use of pyrethroid and indoxacarb pesticides under emergency control, such as pest resistance development, contamination of soil, water, and farm products. This study analyzed the structure and physiological function of the sodium channel in S. frugiperda, which is an important step to elaborate the resistance mechanism of S. frugiperda to indoxacarb and pyrethroid pesticides. According to genetic analysis, the cloned cDNA sequences of sodium channel in S. frugiperda (SfNav) showed the shortest genetic distance with that of the sodium channel in Helicoverpa armigera. Under the induction of three pesticides, the expression of SfNav decreased in the first 12 h and then increased after 24 h. It was concluded that SfNav had a typical structure of the sodium channel of insects and its down-regulated expression can decrease the combination of S. frugiperda with pyrethroid and indoxacarb pesticides. The up-regulated expression of SfNav was conducive to the enhancement of the pesticide resistance.

Spodoptera frugiperda is a polifagous insect of major economic impact in the world. In this study, we assembled and annotated the complete mitochondrial genome of S. frugiperda. The mitochondrial genome length is 15,353 bp, containing 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNA), 2 ribosome RNA genes (rRNA), and 1 D-loop control regions. The overall nucleotide composition is: A of 40.7%, T of 40.3%, C of 11.3% and G of 7.7%, with a total GC content of the mitochondrial genome 19.0% and AT of 81.0%. Phylogenetic and taxonomic analysis based on the amino acid sequences of 13 PCGs from 21 species confirmed the position of S. frugiperda closely related to S. litura and S. exigua. The complete mitochondrial genome of S. frugiperda study is able to provide a reference for the phylogenetic and taxonomic relationships, and also more data for further study of the Nolidae family in China.

The noctuid moth Spodoptera frugiperda (the fall armyworm) is endemic to the Western Hemisphere and appears to be undergoing sympatric speciation to produce two subpopulations that differ in their choice of host plants. The \'rice strain\' and \'corn strain\' are morphologically indistinguishable, requiring the use of genetic markers for identification. Because fall armyworm is a major pest of corn and several other agricultural crops, characterizing the strains has important economic consequences. In this study, comparisons were made of the intron sequences from the triose-phosphate isomerase (Tpi) gene isolated from 85 fall armyworm specimens collected from two host plants. Sixteen new strain-specific haplotypes based on intron polymorphisms are described that can facilitate the characterization of fall armyworm populations associated with different host plants. Comparisons of genetic diversity within and between the strains provides evidence that the corn strain is undergoing active selection and supports the proposal of directional interstrain mating occurring in the wild. Comparisons of the polymorphisms indicate that each intron undergoes different patterns of mutation that in some cases corresponds to host plant preferences. The results confirm that intron sequence comparisons are an effective approach to study fall armyworm population genetics.