High-temperature responses of Myzus persicae and its parasitoid Aphidius gifuensis in relation to heat level, duration and developmental stage.

BACKGROUND: Understanding how parasitoids respond to temperature is crucial for improving biological control strategies under the context of global warming. This study examined the suitability of Myzus persicae and its parasitoid Aphidius gifuensis to varying temperature conditions, as well as the stage-specific response of A. gifuensis to high temperatures. RESULTS: High temperatures had a significant impact on the both M. persicae and A. gifuensis. When exposed to 36°C, M. persicae developed more slowly and produced smaller adults compared to control, regardless of the duration of exposure (2, 4 or 6 h); additionally, the survival rate of M. persicae nymphs sharply decreased under these conditions. Exposure to 36°C for 4 h negatively impacted the development of A. gifuensis. Female parasitoids exposed to 32°C developed into smaller adults, whereas males exposed to all three temperature levels were smaller compared to control group. Female parasitoids exposed to high temperatures, regardless of the specific heat level and duration, exhibited reduced longevity and decreased fecundity. None of the parasitoids exposed to 36°C for 6 h daily developed into adults. Heat treated during early developmental stages (2 and 4 days old) had a greater influence on parasitoid development, whereas heat treatment at 4 and 6 days old had a more significant impact on its fecundity. CONCLUSION: High temperatures not only directly affected the performance of A. gifuensis, but also exerted indirect effects by influencing the quality of the host aphids M. persicae. The deleterious effects of high temperature on larvae can persist into the adult stage, affecting the longevity and reproduction of adults. These findings are important for the utilization of A. gifuensis in the control of M. persicae in warming environments. © 2024 Society of Chemical Industry.

Effects of repeated afidopyropen treatment on the structure and function of the soil microbial community.

Chemical insecticides are the most effective pest control agents. Afidopyropen is a novel insecticide used against sap-sucking insects, such as aphids. However, the effects of repeated afidopyropen application on the structure and function of soil microorganisms remain unknown. In this study, the changes in the enzyme activities, community structure and function, and relative abundance of antibiotic resistance ontology (ARO) of soil microorganisms were investigated during three repeated afidopyropen applications under laboratory conditions at the maximum recommended dosage (M1) and 10 times the M1 (M10). The neutral phosphatase (NPA) and catalase (CAT) activities in the soil were significantly suppressed after afidopyropen treatment. The Simpson diversity index (1/D) and Shannon-Wiener diversity index (H) also decreased in both the M1 and M10 afidopyropen-treated soils, indicating a remarkable decrease in soil microorganism diversity. The average well color development (AWCD) first increased and subsequently recovered to normal levels after the third application of the insecticide, suggesting that afidopyropen application could increase the metabolic activity of soil microorganisms. Metagenomic analysis showed that repeated afidopyropen application in both the M1 and M10 treatment groups altered the community structure of soil microorganisms, albeit in different ways. Furthermore, repeated afidopyropen application significantly increased the relative ARO abundance, especially in the M10 treatment, with the most dominant AROs being adeF, baeS, and IND-6. These findings reveal the effects of excessive afidopyropen application on soil microorganisms and lay an important foundation for the comprehensive evaluation of the impact of this insecticide on the environment.

Persistent toxicity and dissipation dynamics of afidopyropen against the green peach aphid Myzus persicae (Sulzer) in cabbage and chili.

The green peach aphid, Myzus persicae (Sulzer), is a significant global pest in horticultural and field crops. Afidopyropen is a novel systemic insecticide with high efficacy against sucking pests, and it is suitable for the management of M. persicae. However, the persistent toxicity and dissipation dynamics of afidopyropen in vegetables remain unknown. In this study, we determined the residual activity and dissipation dynamics of afidopyropen against M. persicae on cabbage and chili. The data showed that the toxicity of afidopyropen against M. persicae lasted more than 30 days; the corrected mortality was greater than 80% 10 days after application and was 50-60% 30 days post-application. The afidopyropen residues on cabbage and chili plants were quantified using ultrahigh-pressure liquid chromatography-tandem mass spectrometry. The dissipation half-lives of afidopyropen on cabbage and chili plants ranged from 1.45 to 2.34 days and 3.98-5.98 days at different recommended dosages, respectively. Our findings provide valuable data for the maximum residue limits of afidopyropen on vegetables and will help growers determine the frequency and timing of its application on cabbage and chili.

Identification and Characterization of Antioxidant Enzyme Genes in Parasitoid Aphelinus asychis (Hymenoptera: Aphelinidae) and Expression Profiling Analysis under Temperature Stress.

It is well known that high temperature, a typically negative environmental factor, reduces the parasitism of a parasitoid. Generally, high temperature causes the rapid overproduction of reactive oxygen species (ROS) in organisms, and antioxidative enzymes participate in the process of resisting environmental stress by eliminating excess ROS. In the present study, we identify two superoxide dismutase (SOD), one catalase (CAT), six peroxidases (POD), and five glutathione-S-transferase (GST) genes; and the survival rate and antioxidative enzyme patterns under short-term high temperature exposure of the parasitoid wasp, A.asychis, are examined. Survival results of A.asychis reveal that females show higher thermal tolerance than males. Under short-term high-temperature exposure, in females, the expression levels of most antioxidant enzyme genes decreased first and then increased to a peak at 41 °C, while only the expression of AasyGST4 showed a continuous increase. In males, the expression patterns of most antioxidant enzyme genes fluctuated and reached a maximum at 41 °C. Moreover, the expression levels of the majority of antioxidant enzyme genes were higher in females than in males. In addition, at temperatures of and above 35 °C, the activities of these four antioxidant enzymes were induced. The results show that the antioxidant enzymes confer thermo-tolerance to A. asychis against lethal thermal stress. Our observations enrich the understanding of the response mechanism to high-temperature assaults of A. asychis.

Sublethal and transgenerational effects of afidopyropen on biological traits of the green peach aphid Myzus persicae (Sluzer).

The green peach aphid, Myzus persicae (Sulzer), is a cosmopolitan agricultural pest and causes great damages each year. Afidopyropen is a novel insecticide with high efficacy against even the insecticides resistant M. persicae. However, the sublethal and transgenerational effects of afidopyropen on M. persicae is not clear. In the present paper, sublethal and transgenerational effects of afidopyropen on biological traits of M. persicae were determined based on the age-stage, two-sex life table theory. The afidopyropen was more toxic against M. persicae than other widely used insecticides, with LC50 of 0.086 mg/L. The treatment with LC5, LC15 and LC25 concentrations of afidopyropen remarkably reduced the longevity and fecundity of F0M. persicae by 15.9-64.4% and 24.3-76.7%, respectively, compared with those of the control. The life history traits of F1 generation including the pre-adult development time, mean total longevity, pre-adult survival rate, total pre-oviposition period and fecundity were significantly affected after treatment of the F0 with afidopyropen, and the population parameters, including the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) were also remarkably decreased, while the mean generation time (T) was extended by 6.94%. Among four development and reproduction related genes investigated, JHEH was downregulated by 31.8-38.0% in the afidopyropen treated F0 generation, while the EcR and JHAMT were overexpressed and the Vg was significantly downregulated in F1 generation compared to the control group. All these data indicated that the afidopyropen had significant sublethal and transgenerational effects on M. persicae. These results provide insights into comprehensively understanding of the insecticidal effects of afidopyropen on M. persicae as well as the management of resistant M. persicae.