Flupyradifurone resistance in Myzus persicae populations from peach and tobacco in Greece

Flupyradifurone negatively affects survival, physical condition and mobility in the two-spotted lady beetle (Adalia bipunctata)

Lady beetles play a crucial role in natural ecosystems and agricultural settings. Unfortunately, these insects and more specifically the two-spotted lady beetle (Adalia bipunctata) are currently facing a severe decline in populations due to various stressors, with pesticide exposure being a significant threat. Flupyradifurone is a relatively newly introduced insecticide and as existing research is mainly elucidating its effects on bees there remains a limited understanding of its effects on non-hymenopteran insects, including lady beetles. In this study we investigated the impact of acute orally applied flupyradifurone doses on survival and sublethal parameters such as physical condition and mobility on A. bipunctata. Our findings revealed a significant increase in mortality among individuals subjected to flupyradifurone doses of 19 ng/individual (corresponding to >1.5-2.0 ng active substance (a.s.)/mg body weight (bw). The calculated LD50 of flupyradifurone at 48 h was 2.11 ng a.s./mg bw corresponding to an amount of 26.38 ng/individual. Sublethal consequences were observable immediately after pesticide application. Even at doses as low as 2 ng/individual (corresponding to >0.0-0.5 ng a.s./mg bw), flupyradifurone induced trembling and temporary immobility in treated animals. Furthermore, pesticide intoxication led to hypoactivity, with less distance covered and a decline in straightness of locomotion. In conclusion, our study underscores the harmful effects of flupyradifurone on the two-spotted lady beetle at doses notably lower than those affecting bees. These findings stress the importance of additional research to attain a more holistic understanding of pesticide impacts not only on a broader range of non-target arthropods species, but also on various exposure routes as well as lethal and sublethal effects.

Overexpression of CYP6CX4 contributing to field-evolved resistance to flupyradifurone, one novel butenolide insecticide, in Bemisia tabaci from China

Bemisia tabaci is a formidable insect pest worldwide, and exhibits significant resistance to various insecticides. Flupyradifurone is one novel butenolide insecticide and has emerged as a new weapon against B. tabaci, but field-evolved resistance to this insecticide has become a widespread concern. To unravel the mechanisms of field-evolved flupyradifurone resistance, we conducted a comprehensive investigation into susceptibility of twenty-one field populations within the Beijing-Tianjin-Hebei Region of China. Alarmingly, thirteen of these populations displayed varying degrees of resistance, ranging from low to medium levels, and building upon our prior findings, we meticulously cloned and characterized the CYP6CX4 gene in B. tabaci. Our investigations unequivocally confirmed the association between CYP6CX4 overexpression and flupyradifurone resistance in three of the thirteen resistant strains via RNA interference. To further validate our findings, we introduced CYP6CX4 overexpression into a transgenic Drosophila melanogaster line, resulting in a significant development of resistance to flupyradifurone in D. melanogaster. Additionally, homology modeling and molecular docking analyses showed the stable binding of flupyradifurone to CYP6CX4, with binding free energy of -6.72 kcal mol-1. Collectively, our findings indicate that the induction of CYP6CX4 exerts one important role in detoxification of flupyradifurone, thereby promoting development of resistance in B. tabaci.

First monitoring of resistance and corresponding mechanisms in the green peach aphid, Myzus persicae (Sulzer), to registered and unregistered insecticides in Saudi Arabia

Insecticides are widely used as the primary management strategy for controlling Myzus persicae, the devastating pest ravaging various vegetables, fruits, crops, and ornamentals. This study examined the susceptibility of M. persicae field populations to bifenthrin, fosthiazate, acetamiprid, spirotetramat, afidopyropen, and flonicamid while exploring the possible metabolic mechanisms of resistance. The study findings revealed that M. persicae field populations exhibited susceptible-to-moderate resistance to bifenthrin (resistance ratio (RR) = 0.94-19.65) and acetamiprid (RR = 1.73-12.91), low-to-moderate resistance to fosthiazate (RR = 3.67-17.00), and susceptible-to-low resistance to spirotetramat (RR = 0.70-6.68). However, all M. persicae field populations were susceptible to afidopyropen (RR = 0.44-2.25) and flonicamid (RR = 0.40-2.08). As determined by the biochemical assays, carboxylesterases were involved in the resistance cases to bifenthrin and fosthiazate, whereas cytochrome P450 monooxygenases were implicated in the resistance cases to acetamiprid. However, glutathione S-transferases were not implicated in the documented resistance of M. persicae field populations. Overall, the susceptibility of M. persicae field populations to flonicamid and afidopyropen-two unregistered insecticides in Saudi Arabia-suggests their potential as promising chemicals that can expand the various alternatives available for controlling this devastating pest. Although the detected moderate levels of resistance to bifenthrin, fosthiazate, and acetamiprid indicate a shift in the selection pressure of insecticides for M. persicae due to Saudi regulations, which have resulted in eventual obsolescence of conventional insecticides in favor of novel insecticides. Finally, rotational use of aforementioned insecticides can help in managing insecticide resistance in M. persicae.

Identification, Pathogenicity, and Culture Conditions of a New Isolate of Cordyceps javanica (Hypocreales: Cordycipitaceae) From Soil

This study decribes a highly effective insecticidal isolate of Cordyceps javanica (Frieder. & Bally) (Hypocreales: Cordycipitaceae) named IJ-tg19, which was isolated from soil. Spray bioassays were performed with IJ-tg19 on Myzus persicae (Sulzer) (Hemiptera: Aphididae) adults, third-instar nymphs of Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), and third-instar larvae of Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) to determine the pathogenicity of the isolate. The corrected mortality rates for all three pests were 100% when the conidia concentration was 1 × 106 conidia/ml, the lowest concentration in this study, and the median survival times (MST) were 4, 4, and 3 d. The MST shortens with increasing conidia concentration. The effects of laboratory culture conditions on the sporulation and growth of the isolate were also studied. This isolate had the greatest conidia production and fastest growth rate on malt extract agar medium at 25°C. The amount of conidia produced had positive correlation to light duration, with the highest production at 24 hr light. The growth of mycelium can adapt to a moderately alkaline environment, but the optimum conidial production occurred at the pH of 7. Our finding and research will be useful in biocontrol programs that are considering using the new isolate of C. javanica against greenhouse pests.

The dynamic changes of genes revealed that persistently overexpressed genes drive the evolution of cyflumetofen resistance in Tetranychus cinnabarinus

Changes in gene expression are associated with the evolution of pesticide resistance in arthropods. In this study, transcriptome sequencing was performed in 3 different resistance levels (low, L; medium, M; and high, H) of cyflumetofen-resistant strain (YN-CyR). A total of 1 685 genes, including 97 detoxification enzyme genes, were upregulated in all 3 stages, of which 192 genes, including 11 detoxification enzyme genes, showed a continuous increase in expression level with resistance development (L to H). RNA interference experiments showed that overexpression of 7 genes (CYP392A1, TcGSTd05, CCE06, CYP389A1, TcGSTz01, CCE59, and CYP389C2) is involved in the development of cyflumetofen resistance in Tetranychus cinnabarinus. The recombinant CYP392A1 can effectively metabolize cyflumetofen, while CCE06 can bind and sequester cyflumetofen in vitro. We compared 2 methods for rapid screening of resistance molecular markers, including short-term induction and 1-time high-dose selection. Two detoxification enzyme genes were upregulated in the field susceptible strain (YN-S) by induction with 20% lethal concentration (LC₂₀ ) of cyflumetofen. However, 16 detoxification enzyme genes were upregulated by 1-time selection with LC₈₀ of cyflumetofen. Interestingly, the 16 genes were overexpressed in all 3 resistance stages. These results indicated that 1 685 genes that were upregulated at the L stage constituted the basis of cyflumetofen resistance, of which 192 genes in which upregulation continued to increase were the main driving force for the development of resistance. Moreover, the 1-time high-dose selection is an efficient way to rapidly obtain the resistance-related genes that can aid in the development of resistance markers and resistance management in mites.

Comparison of the effectiveness of thiamethoxam and its main metabolite clothianidin after foliar spraying and root irrigation to control Myzus persicae on peach

The green peach aphid, Myzus persicae, is one of the most economically important pests in peach-growing areas around the world. In many countries, the application of insecticides is the main method to control and reduce the population of M. persicae. In this study, we investigated the effects and persistence of thiamethoxam against M. persicae by foliar spraying and root irrigation. The residues of thiamethoxam and clothianidin in peach were determined to assess food safety. The results showed that thiamethoxam treatment significantly reduced the population of M. persicae through foliar spraying and root irrigation. And the persistence of root irrigation on M. persicae was significantly longer than that of spraying. Thiamethoxam and clothianidin were absorbed by the roots, transported to other parts of the plant, and concentrated in the leaves, especially new leaves. The final residues of thiamethoxam and clothianidin in peaches were below the maximum residue limit (MRLs). These results suggested that thiamethoxam is more effective in M. persicae control through root irrigation than foliar spraying. The persistence of root irrigation on M. persicae was significantly longer than that of spraying. These results shed some light upon the control of M. persicae by root irrigation of thiamethoxam.

Target site mutations underlying insecticide resistance in Tunisian populations of Myzus persicae (Sulzer) on peach orchards and potato crops

BACKGROUND

The massive use of synthetic insecticides strongly affects the level of insecticide resistance in populations of Myzus persicae worldwide. The selection of target site insensitivity-mutations is particularly worrying in areas where agro-industrial crops are vulnerable to the attacks of aphids that vector viruses, as in the case of Tunisia. Knowledge of the resistance mechanisms evolved locally in this aphid pest is a prerequisite to improving and retaining the sustainability of integrated pest management strategies.

RESULTS

Target site mutations were surveyed in several populations of M. persicae collected from peach and potato crops between 2011 and 2017 in three Tunisian regions using real-time allele-specific PCR. The L1014F mutation (kdr locus) was found at a moderate frequency mostly in the heterozygous state and the homozygous resistant genotype was very uncommon. The M918T mutation (super-kdr locus) was present in a few heterozygous individuals, whereas the M918L mutation was detected for the first time in Tunisia and extreme North Africa. This latter mutation was shown to be widespread and well-established in Tunisia mainly as homozygous individuals, and was more abundant on peach than on potato crops. The S431F mutation (MACE) was found in a few heterozygous individuals. No individuals carrying the R81T mutation linked to neonicotinoid resistance were detected.

CONCLUSION

This study points out a critical situation for the efficacy of pyrethroid insecticides to control M. persicae populations in Tunisia. It also confirms the rapid spread of the M918L mutation which has been detected in many different areas of the Mediterranean basin. © 2022 Society of Chemical Industry.