Li Cui

Helicoverpa armigera (Lepidoptera: Noctuidae) is a globally significant agricultural pest with documented resistance to various insecticides. Rapid and accurate diagnostic tools for assessing insecticide susceptibility are urgently needed to enhance the efficiency of pest control for farmers. The modified centrifuge tube bioassay diagnostic kit provides detection results within 3 h, identifying the diagnostic doses as 5087.32 ng/cm ² for indoxacarb, 300.35 ng/cm ² for chlorpyrifos and 461.79 ng/cm ² for chlorantraniliprole. A regression equation was established to correlate mortalities at diagnostic doses with actual resistance ratios in various populations of H. armigera using the leaf‐dipping method. The diagnostic mortality of H. armigera showed a negative correlation with actual resistance ratios to indoxacarb ( r = −0.9674, p = 0.0070), chlorpyrifos ( r = −0.8474, p = 0.0696) and chlorantraniliprole ( r = −0.8833, p = 0.0470). Furthermore, the validation of kit accuracy was applied to field populations in the Handan region of China, selected from the years 2017, 2018 and 2019. The datasets of chlorpyrifos and chlorantraniliprole displayed a strong correlation ( r = 0.9968, p < 0.001). Nevertheless, the diagnostic dose of LD ₉₀ failed to promptly reveal the resistance level to indoxacarb in the Handan regions (ranging from 19.25 to 29.48 fold), suggesting that these kits are constrained by the detection threshold of the equation. In conclusion, a diagnostic kit based on has been developed for the rapid and accurate detection of susceptibility to these three insecticides in H. armigera . This insecticide diagnostic kit for H. armigera serves as a preliminary, accessible and cost‐effective screening tool for identifying effective insecticides.

Myzus persicae is a worldwide insect pest with high resistance to many traditional insecticides. Cycloxaprid, a novel cis-configuration neonicotinoid insecticide, is effective in controlling neonicotinoid-resistant insect pests. Lethal and sublethal effects of cycloxaprid on M. persicae were conducted in this study. Results showed that cycloxaprid had higher toxicity to the laboratory and field resistant M. persicae than imidacloprid. Because of the resistance, imidacloprid showed lower control efficacy (84.79%) against M. persicae in the field. In addition, in order to quantify the sublethal impacts of cycloxaprid, we conducted a life table analysis on M. persicae. When resistant M. persicae was treated with LC₂₅ of cycloxaprid or imidacloprid, the longevity and fecundity of F₁ adults were significantly decreased. Meanwhile, the intrinsic rate of increase (r_m), finite rate of increase (λ) and net reproduction rate (R_i) of F1 generation M. persicae were reduced in cycloxaprid and imidacloprid treatments. Therefore, cycloxaprid shows high potential as a candidate insecticide for managing imidacloprid-resistant M. persicae. Importantly, our laboratory data indicate that exposure to its low sublethal concentration (LC₂₅) inhibits population growth parameters, suggesting a low risk of inducing pest resurgence under such conditions.

The ryanodine receptors (RyRs) represent an optimal target for insecticide development. To explore novel structures of RyRs agonists, a series of compounds containing 1,2,4-oxadiazole were designed and synthesized based on the RyRs structure. The compounds were confirmed by ¹H and ¹³C nuclear magnetic resonance as well as high-resolution mass spectrometry. Additionally, bioassays demonstrated that the majority of the newly synthesized compounds exhibited complete mortality (100%) against Plutella xylostella and Mythimna separata at a concentration of 50 mg/L. Furthermore, compound II5 showed a slightly higher LC₅₀ value (LC₅₀ = 0.20 mg/L) compared to the control chlorantraniliprole (LC₅₀ = 0.06 mg/L) against M. separata. Through the toxicity study of the target compounds on Spodoptera frugiperda carrying the resistant mutant RyR (I4790M), it was confirmed that these target compounds have a similar mode of action to chlorantraniliprole. Moreover, the binding modes of these compounds were investigated, revealing that 1,2,4-oxadiazole serves as an effective substitute structure for amide bonds. These findings provide valuable insights for further structural optimization.

In mountainous citrus orchards, the application of conventional ground sprayers for the control of citrus red mite (Panonychus citri) is often constrained by complex terrain and low operational efficiency. The Unmanned Aerial Spraying System (UASS), due to its low-altitude, low-volume, and high-maneuverability characteristics, has emerged as a promising alternative for pest management in such challenging environments. To evaluate the spray performance and field efficacy of different UASS types in controlling P. citri, five representative UASS models (JX25, DP, T1000, E-A2021, and T20), four mainstream pesticide formulations, and four novel tank-mix adjuvants were systematically assessed in a field experiment conducted in a typical hilly citrus orchard. The results showed that T20 delivered the best overall spray deposition, with upper canopy coverage reaching 10.63%, a deposition of 3.01 μg/cm², and the highest pesticide utilization (43.2%). E-A2021, equipped with a centrifugal nozzle, produced the finest droplets and highest droplet density (120.3–151.4 deposits/cm²), but its deposition and coverage were lowest due to drift. Nonetheless, it exhibited superior penetration (dIPR 72.3%, dDPR 73.5%), facilitating internal canopy coverage. T1000, operating at higher flight parameters, had the weakest deposition. Formulation type had a limited impact, with microemulsions (MEs) outperforming emulsifiable concentrates (ECs) and suspension concentrates (SCs). All adjuvants improved spray metrics, especially Yimanchu and Silwet, which enhanced pesticide utilization to 46.8% and 46.4% for E-A2021 and DP, respectively. Adjuvant use increased utilization by 4.6–11.9%, but also raised ground losses by 1.5–4.2%, except for Yimanchu, which reduced ground loss by 2.3%. In terms of control effect, the rapid efficacy (1–7 days after application, DAA) of UASS spraying was slightly lower than that of ground sprayers—electric spray gun (ESG), while its residual efficacy (14–25 DAA) was slightly higher. The addition of adjuvants improved both rapid and residual efficacy, making it comparable to or even better than ESG. E-A2021 with 5% abamectin·etoxazole ME (5A·E) and Yimanchu achieved 97.4% efficacy at 25 DAA. Among UASSs, T20 showed the rapid control, while E-A2021 outperformed JX25 and T1000 due to finer droplets effectively targeting P. citri. In residual control (14–25 DAA), JX25 with 45% bifenazate·etoxazole SC (45B·E) was most effective, followed by T20. 5A·E and 45B·E showed better residual efficacy than abamectin-based formulations, which declined more rapidly. Adjuvants significantly extended control duration, with Yimanchu performing best. This study demonstrates that with optimized spraying parameters, nozzle types, and adjuvants, UASSs can match or surpass ground spraying in P. citri control in hilly citrus orchards, providing valuable guidance for precision pesticide application in complex terrain.

On the basis of the structures of natural methylxanthines and chalcone, a series of novel chalcone analogues containing a methylxanthine moiety, Ia-Ig, and their N-acyl pyrazoline derivatives IIa-IIz and IIaa-IIaf were synthesized and identified through melting points, ¹H NMR, ¹³C NMR, and HRMS. The single crystal of compound IId was obtained, which further illustrated the structural characteristics of the methylxanthine-acylpyrazoline compounds. The biological tests showed that some of them displayed favorable insecticidal activities toward Plutella xylostella L. and were superior to the natural methylxanthine compound caffeine while being comparable with the insecticide triflumuron (e.g., compound Ic: LC₅₀ = 16.8508 mg/L, IIf: LC₅₀ = 1.5721 mg/L, against P. xylostella). Of these compounds, Ic, IIf, and IIu could serve as novel insecticidal leading structures for further study. Some of the compounds showed good fungicidal activities (e.g., compound Ig: EC₅₀ = 14.74 μg/mL, against Rhizoctonia cerealis; IIf: EC₅₀ = 7.06 μg/mL, against Physalospora piricola; IIac: EC₅₀ = 5.37 and 8.19 μg/mL, against Phytophthora capsici and Sclerotinia sclerotiorum, respectively); Ic, Ig, IIa, IIf, IIr, IIs, IIv, IIac, and IIaf could be novel fungicidal leading compounds for further exploration. Furthermore, most of the tested compounds exhibited apparent herbicidal activities against Brassica campestris at a concentration of 100 μg/mL; among others, compound IIa was the best one both toward Brassica campestris and Echinochloa crusgalli and deserves further investigation. The structure-activity relationships of these compounds were also summarized and discussed in detail. The contrast experiment results of compounds C-1 and C-2 showed a positive effect on the biological activity enhancement from the combination of the methylxanthine moiety with the N-dichloroacetyl phenylpyrazoline skeleton. In addition, two 3D-QSAR models with predictive capability were constructed based on the insecticidal and fungicidal activities to afford deep insight into the bioactivity profiles of these compounds. This research provides useful guidance and reference for the discovery and development of novel xanthine natural product-based pesticides.

BACKGROUND: Fall armyworm (Spodoptera frugiperda) is one of the major invasive pests in China, and has been widely controlled by labor‐intensive foliar sprays of agrochemicals in maize (Zea mays L.).RESULTS: Systemic bioassay showed that mixtures of chlorantraniliprole (Chlor) and carbaryl (Carb) had dramatically synergistic effect on toxicity to S. frugiperda. Particularly, a mixture of Chlor with Carb at a mass ratio of 2:1 (MCC) exhibited the highest toxicity to S. frugiperda. Therefore, seed treatment of Chlor mixed with Carb was studied as a simple, accurate, efficient and low‐cost control technology. Our results showed that MCC treatment shortened the median lethal time and 90% lethal time to S. frugiperda compared to Chlor‐ and Carb‐alone treatments. Meanwhile, smaller leaf consumption by S. frugiperda was recorded under MCC treatment compared to Chlor‐ and Carb‐alone treatments. In field trial, maize‐seed treatment with MCC showed efficacy up to 39 days post‐emergence in preventing S. frugiperda foliar damage at a low infestation pressure. Moreover, chemical quantification by ultrahigh‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) showed that Chlor residues were more absorbed and concentrated in maize leaves of MCC treatment, compared to that of Chlor‐alone treatment.CONCLUSION: These results suggested that seed treatment with MCC can be applied to increase the control efficacy and reduce the cost of Chlor‐alone treatment for controlling S. frugiperda. The present study provided evidence of an enhanced translocation and accumulation of Chlor residues in maize leaves under MCC treatment, which likely contributed to a synergistic effect against S. frugiperda. © 2022 Society of Chemical Industry.