Fusarium equiseti (JMF-01), as an entomopathogenic fungus, can effectively control agricultural pests and has the potential to be a biocontrol agent. To promote mycelial growth and sporulation, we investigated the optimal submerged culture conditions for F. equiseti. In this study, we used the single-factor method and Box–Behnken design and determined the virulence of the submerged culture against Myzus persicae after optimization. As a result, the highly significant factors affecting the spore concentration of strain JMF-01 were the primary inoculum density and the initial pH, and the highly significant factor affecting the mycelial biomass was the medium-to-flask ratio. The highest mycelial biomass value was 0.35 g when the incubation time was 5.68 days, the initial pH was 5.11, the medium-to-flask ratio was 0.43, and 1 mL of the primary inoculum with spore density of 0.97 × 10⁷ conidia/mL was added. When the incubation time was 6.32 days, the initial pH was 4.46, the medium-to-flask ratio was 0.35, the primary inoculum density was 1.32 × 10⁷ conidia/mL of 1 mL, and the highest spore concentration of 6.49 × 10⁸ blastospores/mL was obtained. Compared with the unoptimized medium conditions, the optimized submerged culture had the highest mycelial biomass and spore concentration, which were 3.46 and 2.06 times higher, respectively. The optimized submerged culture was highly pathogenic toward M. persicae, reaching a 95% mortality rate. Our results provide optimal submerged culture conditions for F. equiseti and lay the basis for later research to expand production for pest control.

Compared with single insecticides, insecticide mixtures can enhance efficacy, broaden the spectrum of activity, and potentially delay resistance evolution in Aphis gossypii. However, their sublethal and intergenerational effects remain poorly understood. Here, the life table analysis was used to evaluate the effects of mixture treatments prepared from sublethal (LC₂₀) and low-lethal (LC₅₀) doses of nitenpyram, pymetrozine, and beta-cypermethrin on the directly exposed F₀ generation of A. gossypii and its effects on the F₁ progeny. Total protein, free amino acid, and vitellogenin (Vg) contents were measured, and the sequence and expression of Vg and vitellogenin receptor (VgR) genes were analyzed. Exposure to the mixture treatments significantly reduced longevity and fecundity in both generations while increasing total protein and free amino acid contents. Domain prediction confirmed the conserved structural features of AgVg and AgVgR, and phylogenetic analysis showed that both clustered with homologs from closely related aphid species. RT-qPCR further revealed that the mixture treatments significantly suppressed AgVg and AgVgR expression. In conclusion, exposure to the mixture treatments affects both directly exposed individuals and their progeny, providing a basis for evaluating the ecological consequences of insecticide mixtures and optimizing their use within integrated pest management strategies for A. gossypii.

Chinese wolfberry (Lycium barbarum L.), a specialty crop of ecological, medical and economic values in Ningxia province of China, is subjected to severe Aphis gossypii Glover damage. Currently, A. gossypii populations showing extremely high-level resistance to beta-cypermethrinin in the major wolfberry planting areas in Ningxia. The specific resistance mechanisms, however, are still not known. In this work, we collected a field A. gossypii strain (HSP) from a wolfberry orchard of Ningxia in 2021 using a single-time sampling method and its resistance to beta-cypermethrin was determined to be extremely high (994.74‒fold) as compared with a susceptible strain (SS). Then we explored the potential resistance mechanisms from two aspects of metabolic detoxification and target-site alterations. Bioassay of beta-cypermethrin with or without the synergist showed that piperonyl butoxide (PBO) significantly increased the toxicity of beta-cypermethrin (4.72‒fold) to the HSP strain while triphenyl phosphate (TPP) and diethyl maleate (DEM) exhibited no significant synergistic effects. Correspondingly, the O-demethylase activity of the cytochrome P450s in the HSP strain was 1.68‒fold higher than that in the susceptive strain (SS), whereas changes of carboxylesterases and glutathione S-transferases in their activities were unremarkable. Also, fifteen upregulated P450 genes were identified by both RNA-Seq and qRT-PCR technologies, containing eleven CYP6 genes, three CYP4 genes and one CYP380 gene. Especially, five CYP6 genes of high relative expression levels (> 3.00‒fold) were intensively expressed by the beta-cypermethrin induction in the HSP aphids. These metabolism-related results indicate the key role of the P450-mediated metabolic detoxification in the HSP resistance to beta-cypermethrin. Sequencing of voltage-gated sodium channel (VGSC) genes identified a prevalent M918L mutation and a new G1012D mutation in the HSP A. gossypii. Moreover, heterozygous 918M/L and 918M/L+G1012D mutations were the dominant genotypes with frequencies of 60.00% and 36.67% in the HSP population, respectively. Overall, VGSC mutations along with P450-mediated metabolic resistance were contributed to the extremely high resistance of the HSP wolfberry aphids to beta-cypermethrin, providing support for A. gossypii control and resistance management in the wolfberry planting areas of Ningxia using insecticides with different modes of action.

Chinese wolfberry (Lycium barbarum L.), a specialty crop with ecological, medical, and economic value in Ningxia province of China, is subject to severe damage from Aphis gossypii Glover. Currently, A. gossypii populations show extremely high-level resistance to beta-cypermethrin in the major wolfberry planting areas in Ningxia. The specific resistance mechanisms, however, are still not known. In this work, we collected a field A. gossypii strain (HSP) from a wolfberry orchard in Ningxia in 2021 using a single-time sampling method, and its resistance to beta-cypermethrin was determined to be extremely high (994.74-fold) as compared with that of a susceptible strain (SS). Then we explored the potential resistance mechanisms from two aspects, namely, metabolic detoxification and target-site alterations. Bioassays of beta-cypermethrin with or without a synergist showed that piperonyl butoxide (PBO) significantly increased the toxicity of beta-cypermethrin (4.72-fold) to the HSP strain, while triphenyl phosphate (TPP) and diethyl maleate (DEM) exhibited no significant synergistic effects. Correspondingly, the O-demethylase activity of cytochrome P450s in the HSP strain was 1.68-fold higher than that in the susceptive strain (SS), whereas changes in carboxylesterases and glutathione S-transferases activities were unremarkable. Also, fifteen upregulated P450 genes were identified by both RNA-Seq and qRT-PCR technologies, containing eleven CYP6 genes, three CYP4 genes, and one CYP380 gene. Especially, five CYP6 genes with high relative expression levels (>3.00-fold) were intensively expressed by beta-cypermethrin induction in the HSP aphids. These metabolism-related results indicate the key role of P450-mediated metabolic detoxification in HSP resistance to beta-cypermethrin. Sequencing of voltage-gated sodium channel (VGSC) genes identified a prevalent M918L mutation and a new G1012D mutation in HSP A. gossypii. Moreover, heterozygous 918 M/L and 918 M/L + G1012D mutations were the dominant genotypes with frequencies of 60.00% and 36.67% in the HSP population, respectively. Overall, VGSC mutations along with P450-mediated metabolic resistance contributed to the extremely high resistance of the HSP wolfberry aphids to beta-cypermethrin, providing support for A. gossypii control and resistance management in the wolfberry planting areas of Ningxia using insecticides with different modes of action.