Molecular and functional characterization of heat-shock protein 70 in Aphis gossypii under thermal and xenobiotic stresses.

Aphis gossypii, a globally distributed and economically significant pest of several crops, is known to infest a wide range of host plants. Heat shock proteins (Hsps), acting as molecular chaperones, are essential for the insect's environmental stress responses. The present study investigated the molecular characteristics and expression patterns of AgHsp70, a heat shock protein gene, in Aphis gossypii. Our phylogenetic analysis revealed that AgHsp70 shared high similarity with homologs from other insects, suggesting a conserved function across species. The developmental expression profiles of AgHsp70 in A. gossypii showed that the highest transcript levels were observed in the fourth instar nymphs, while the lowest levels were detected in the third instar nymphs. Heat stress and exposure to four different xenobiotics (2-tridecanone, tannic acid, gossypol, and flupyradifurone (4-[(2,2-difluoroethyl)amino]-2(5H)-furanone)) significantly up-regulated AgHsp70 expression. Knockdown of AgHsp70 using RNAi obviously increased the susceptibility of cotton aphids to 2-tridecanone, gossypol and flupyradifurone. Dual-luciferase reporter assays revealed that gossypol and flupyradifurone significantly enhanced the promoter activity of AgHsp70 at a concentration of 10 mg/L. Furthermore, we identified the transcription factor heat shock factor (HSF) as a regulator of AgHsp70, as silencing AgHSF reduced AgHsp70 expression. Our results shed light on the role of AgHsp70 in xenobiotic adaptation and thermo-tolerance.

The sulfoximine insecticide sulfoxaflor exposure reduces the survival status and disrupts the intestinal metabolism of the honeybee Apis mellifera.

Honeybees (Apis mellifera) are indispensable pollinators in agricultural production, biodiversity conservation, and nutrients provision. The abundance and diversity of honeybees have been rapidly diminishing, possibly related to the extensive use of insecticides in ecosystems. Sulfoxaflor is a novel sulfoximine insecticide that, like neonicotinoids, acts as a competitive modulator of nicotinic acetylcholine receptors (nAChR) in insects. However, few studies have addressed the negative effects of sulfoxaflor on honeybees at environmentally relevant concentrations. In the present study, adult workers were fed a 50% (w/v) of sugar solution containing different concentrations (0, 0.05, 0.5 and 2.0 mg/L) of sulfoxaflor for two weeks consecutively. The survival rates, food intake, and body weight of the honeybees significantly decreased after continuous exposure at higher doses (0.5 and 2.0 mg/L) of sulfoxaflor when compared with the control. The change in the metabolites in the honeybee gut was determined using high-throughput non-targeted metabolomics on day 14 after sulfoxaflor treatment. The results revealed that 24 and 105 metabolites changed after exposure to 0.5 and 2.0 mg/L sulfoxaflor, respectively, compared with that of the control groups. A total of 12 changed compounds including pregenolone and glutathione were detected as potential biomarkers, which were eventually found to be enriched in pathways of the steroid hormone biosynthesis (p = 0.0001) and glutathione metabolism (p = 0.021). These findings provide a new perspective on the physiological influence of sulfoxaflor stress in honeybees.

Toxicity and risk assessment of nine pesticides on nontarget natural predator Harmonia axyridis (Coleoptera: Coccinellidae).

BACKGROUND: Harmonia axyridis (Coleoptera: Coccinellidae) is a beneficial predatory arthropod in the agricultural ecosystem. For the success and development of integrated pest management strategies, it is essential to assess the toxicity risks of commonly used pesticides to nontarget arthropods. RESULTS: The glass tube residue method was used to determine the risk of nine pesticides to H. axyridis after second-instar exposure. To assess the potential risk of the selected pesticides, the pre-adult LR50 values were calculated by the hazard quotient (HQ) method. The LR50 (application rate causing 50% mortality) values of imidacloprid, dinotefuran, thiamethoxam, acetamiprid, bifenthrin, and dimethoate were 0.44, 0.82, 0.10, 0.05, 0.04, and 0.21 g a.i. ha-1 , respectively, showing unacceptable risk to H. axyridis after exposure to in and off field. However, emamectin benzoate and two fungicides, tebuconazole and myclobutanil, posed a low risk to H. axyridis and their HQ values were less than the trigger value of 5. CONCLUSIONS: The four neonicotinoid insecticides (imidacloprid, dinotefuran, thiamethoxam, and acetamiprid), pyrethroid bifenthrin, and organophosphorus dimethoate showed a high risk to H. axyridis. Emamectin benzoate, tebuconazole, and myclobutanil showed a low risk to H. axyridis under both exposure scenarios. The results provide critical scientific evidence to guide future regulation of pesticide management practices and protection of nontarget arthropods like H. axyridis. © 2022 Society of Chemical Industry.

Comparative sensitivity of Neoseiulus cucumeris and its prey Tetranychus cinnabarinus, after exposed to nineteen pesticides.

The toxicity tests of nineteen commonly used pesticides were carried out to compare the sensitivity differences between predatory mite Neoseiulus cucumeris and its prey Tetranychus cinnabarinus by a "leaf spray method" in laboratory microcosms. For two avermectins, emamectin benzoate and abamectin, exhibited high bioactivity against T. cinnabarinusf with LR50 values of 0.04 and 0.05 g a.i./ha, respectively, but these two insecticides showed the opposite toxic effects to N. cucumeris. These two agents showed strong selectivity for the two test species with Selective Toxicity Rate (STR) values of 950 and 620, respectively. However, for five neonicotinoids, the LR50s of dinotefuran, thiamethoxam, imidacloprid, and acetamiprid were all greater than the recommended rates in the field except for clothianidin, and they showed no obvious toxicity difference to the two species with STR values ranging from 0.58 to 2.00. For two organophosphates, malathion is more toxic to N. cucumeris than T. cinnabarinus, however, dimethoate showed a higher toxic effect on T. cinnabarinus. In addition, the toxicity of four pyrethroids, bifenthrin, deltamethrin, cyhalothrin and gamma-cyhalothrin to N. cucumeris was higher than that of T. cinnabarinus, except for alpha-cypermethrin. For five acaricides, spirodiclofen, spirotetramat and pyridaben had no obvious selectivity to the two organisms, while diafenthiuron and chlorfenapyr were found to be highly toxic to T. cinnabarinus than N. cucumeris with STR values of 14.2 and 68.5, respectively. Thus, some pesticides above-mentioned like emamectin benzoate, abamectin, diafenthiuron and chlorfenapyr exhibited potential to be used in the management programs of T. cinnabarinus, especially in organically based production systems where there are fewer chemical control measures available, which need to combine with natural enemies to achieve the best control effect.

Comparative susceptibility of thirteen selected pesticides to three different insect egg parasitoid Trichogramma species.

The parasitoid Trichogramma species are indispensable natural enemies of many lepidopterans and it plays an important role in integrated pest management (IPM) programs throughout the world. Laboratory studies were conducted to compare the susceptibility of three Trichogramma egg parasitoid species to ten common insecticides and three herbicides. The adults of Trichogramma dendrolimi, T. chilonis, and T. ostriniae were exposed to the above-mentioned pesticides by a glass-vial residue method. Among the four neonicotinoids, dinotefuran and thiamethoxam exhibited extremely toxic effects on the Trichogramma dendrolimi and T. chilonis, with Risk Quotient (RQ) values ranging from 1471.2 to 5492.5. However, these two neonicotinoids have a relatively low toxicity to T. ostriniae, with RQ values 433.6 and 915.4, respectively. In addition, Imidacloprid and acetamiprid were slightly to moderately toxic to all the tested parasitic wasps and their RQ values are less than 500. For pyrethroids, all the selected compounds were slightly to moderately toxic to three Trichogramma species except that cyhalothrin was dangerously toxic to T. dendrolimi and T. chilonis, with RQ values 2567.6 and 3950.4. Among the three herbicides tested, pendimethalin, butralin and napropamid were slightly to moderately toxic to egg parasitoids, with all RQ values below 1000. For two avermectins, abamectin were slightly to moderately toxic to all three wasps with RQ values 635.6, 148.3 and 254.2, respectively. However, emamectin benzoate was found to be safe for the parasitoids. Furthermore, T. dendrolimi showed higher sensitivity than T. chilonis and T. ostriniae to the pesticides based on the comparison of LR50 (application rate causing 50% mortality) values. The present results provide informative data for implementing biological and chemical control strategies in integrated pest management.