Design, synthesis, and evaluation of novel arecoline-linked amino acid derivatives for insecticidal and antifungal activities.

A series of arecoline derivatives with amino acid moieties were designed and synthesised using an acylamide condensation strategy, taking arecoline as the foundational structure. The insecticidal efficacy of these compounds against Aphis craccivora and Tetranychus cinnabarinus was evaluated. Notably, derivatives 3h and 3i demonstrated superior insecticidal activity compared with arecoline. Additionally, 3h and 3i showed good fungicidal effectiveness against two types of plant fungi. Moreover, molecular docking analyses suggested that 3h and 3i could affect the nervous systems of A. craccivora and T. cinnabarinus by binding to neuronal nicotinic acetylcholine receptors. These findings suggest that compounds 3h and 3i represent promising leads for further development in insecticide and fungicide research.

Identification of azukisapogenol triterpenoid saponins from Oxytropis hirta Bunge and their aphicidal activities against pea aphid Acyrthosiphon pisum Harris.

BACKGROUND: Acyrthosiphon pisum Harris is the most destructive pest worldwide because of its ability to feed on plants directly and transmit plant viruses as a vector. This study aims to identify triterpenoid saponins from Oxytropis hirta Bunge as biopesticides to control aphids. RESULTS: Three new azukisapogenol triterpenoid saponins (1-3), a new pinoresinol lignan glycoside (8), and four known saponins (4-7) were identified from the root of O. hirta. Compounds 4-7 displayed significant aphicidal activities against A. pisum with oral toxicities (LC50  = 51.10-147.43 µg/mL, 72 h), deterrent effects (deterrence index = 1.00, 100-200 µg/mL, 24 h), and aphid reproduction inhibitory effects (inhibition rates = 75.91-86.73%, 400 µg/mL, 24 h), respectively. The carboxyl groups at C-3 GlcA and C-30 were functional groups for their aphicidal activities. The toxic symptoms caused by the optimal 5 involved insect body-color changes from light green to dark or gray-green, and then brown until death. The intestinal cavity, apical microvilli, nuclei, mitochondria, and electron dense granules in the midgut tissues of A. pisum were the target sites showing aphicidal activity. The suppression of pepsin and α-amylase, and the activation of lipase and trypsin could be the signs of organelle damage in the midgut tissues. CONCLUSION: Azukisapogenol triterpenoid saponins from O. hirta could be used as biopesticides to control aphids for their multiple efficacies, including oral toxicity, deterrent activity, and reproduction inhibitory activity. The toxic symptoms involved insect body-color changes. Midgut tissues and their related enzymes were the targets for saponins showing aphicidal activities. © 2022 Society of Chemical Industry.

Afidopyropen, a novel insecticide originating from microbial secondary extracts.

Afidopyropen, a novel insecticide, is a derivative of pyripyropene A, which is produced by the filamentous fungus Penicillium coprobium. Afidopyropen has strong insecticidal activity against aphids and is currently used as a control agent of sucking pests worldwide. In this study, we summarized the biological properties and field efficacies of its derivatives against agricultural pests using official field trials conducted in Japan. Afidopyropen showed good residual efficacies against a variety of aphids, whiteflies and other sucking pests under field conditions. Furthermore, toxicological studies revealed its safety profiles against nontarget organisms, such as the honeybee, natural enemies and other beneficial insects, as well as mammals. Thus, afidopyropen is a next-generation agrochemical for crop protection that has a low environmental impact.

Chemosensory Proteins Are Associated with Thiamethoxam and Spirotetramat Tolerance in Aphis gossypii Glover.

Chemosensory proteins (CSPs) are a class of transporters in arthropods. Deeper research on CSPs showed that CSPs may be involved in some physiological processes beyond chemoreception, such as insect resistance to pesticides. We identified two upregulated CSPs in two resistant strains of Aphis gossypii Glover. To understand their role in the resistance of aphids to pesticides, we performed the functional verification of CSP1 and CSP4 in vivo and in vitro. Results showed that the sensitivity of the thiamethoxam-resistant strain to thiamethoxam increased significantly with the silencing of CSP1 and CSP4 by RNAi (RNA interference), and the sensitivity of the spirotetramat-resistant strain to spirotetramat increased significantly with the silencing of CSP4. Transgenic Drosophila melanogaster expressing CSPs exhibited stronger resistance to thiamethoxam, spirotetramat, and alpha-cypermethrin than the control did. In the bioassay of transgenic Drosophila, CSPs showed different tolerance mechanisms for different pesticides, and the overexpressed CSPs may play a role in processes other than resistance to pesticides. In brief, the present results prove that CSPs are related to the resistance of cotton aphids to insecticides.

Antimicrobial, Insecticidal and Cytotoxic Activity of Linear Venom Peptides from the Pseudoscorpion Chelifer cancroides.

Linear cationic venom peptides are antimicrobial peptides (AMPs) that exert their effects by damaging cell membranes. These peptides can be highly specific, and for some, a significant therapeutic value was proposed, in particular for treatment of bacterial infections. A prolific source of novel AMPs are arthropod venoms, especially those of hitherto neglected groups such as pseudoscorpions. In this study, we describe for the first time pharmacological effects of AMPs discovered in pseudoscorpion venom. We examined the antimicrobial, cytotoxic, and insecticidal activity of full-length Checacin1, a major component of the Chelifer cancroides venom, and three truncated forms of this peptide. The antimicrobial tests revealed a potent inhibitory activity of Checacin1 against several bacteria and fungi, including methicillin resistant Staphylococcus aureus (MRSA) and even Gram-negative pathogens. All peptides reduced survival rates of aphids, with Checacin1 and the C-terminally truncated Checacin11-21 exhibiting effects comparable to Spinosad, a commercially used pesticide. Cytotoxic effects on mammalian cells were observed mainly for the full-length Checacin1. All tested peptides might be potential candidates for developing lead structures for aphid pest treatment. However, as these peptides were not yet tested on other insects, aphid specificity has not been proven. The N- and C-terminal fragments of Checacin1 are less potent against aphids but exhibit no cytotoxicity on mammalian cells at the tested concentration of 100 µM.

Identification and Functional Analysis of Differentially Expressed Genes in Myzus persicae (Hemiptera: Aphididae) in Response to Trans-anethole.

Plant essential oils, with high bioactivity and biodegradability, provide promising alternatives to synthetic pesticides for pest control. Trans-anethole is the major component of essential oil from star anise, Illicium verum Hook. The compound has a strong contact toxicity against the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), which is a major insect pest of many vegetables and crops. However, little information is known about how M. persicae responds to trans-anethole at the molecular level. We conducted a comparative transcriptome analysis of M. persicae in response to a LD50 dose of trans-anethole. A total of 559 differentially expressed genes were detected in the treated individuals, with 318 genes up-regulated, and 241 genes down-regulated. Gene ontology (GO) analysis revealed that these genes were classified into different biological processes and pathways. We also found that genes encoding ATP-binding cassette (ABC) transporters, DnaJ, and cuticle proteins were dramatically up-regulated in response to trans-anethole. To study the function of these genes, we performed RNA interference (RNAi) analysis. Knockdown of an ABC transporter gene (ABCG4) and a DnaJ gene (DnaJC1) resulted in a significantly increased mortality rate in M. persicae following trans-anethole exposure, indicating the involvement of these two genes in the toxicity response to trans-anethole. The findings provide new insights into the mechanisms of M. persicae in coping with plant essential oils.

Evaluation and optimization of the protocols for measuring cytochrome P450 activity in aphids.

Insect cytochrome P450 plays major roles in detoxification of phytotoxin and insecticides. However, determination of P450 activity in aphids has variable success and there is no reliable method yet. In this study, we found that homogenizing the green peach aphid, Myzus persicae, in the 96-well microplate resulted in significantly higher P450 activities than those in Eppendorf tube. Homogenizing aphids in Eppendorf tube released uncharacterized compounds that inhibited aphids and pig liver P450 activities, whereas aphids homogenized in the microplate may not be completely ground and thus released fewer such inhibitors. Then, the microplate homogenization method was optimized as follows: one or two aphids were placed in one well of the 96 well-microplate and ground in phosphate buffer using pipette tips for 20 cycles, followed by addition of 7-ethoxycoumarin, and then incubated for 1 h at room temperature, after which glycine buffer-ethanol mixture was added to stop the reaction. This method is also suitable for the pea aphid, Acyrthosiphon pisum, and the bird cherry-oat aphid, Rhopalosiphum padi. These results highlight the importance of considering inhibitory effects of endogenous compounds in insects on their P450 activities and provide one possible method to reduce these inhibitory effects.

Effects of imidacloprid and thiamethoxam on the development and reproduction of the soybean aphid Aphis glycines.

The soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) is a primary pest of soybeans and poses a serious threat to soybean production. Our studies were conducted to understand the effects of different concentrations of insecticides (imidacloprid and thiamethoxam) on A. glycines and provided critical information for its effective management. Here, we found that the mean generation time and adult and total pre-nymphiposition periods of the LC50 imidacloprid- and thiamethoxam-treatment groups were significantly longer than those of the control group, although the adult pre-nymphiposition period in LC30 imidacloprid and thiamethoxam treatment groups was significantly shorter than that of the control group. Additionally, the mean fecundity per female adult, net reproductive rate, intrinsic rate of increase, and finite rate of increase of the LC30 imidacloprid-treatment group were significantly lower than those of the control group and higher than those of the LC50 imidacloprid-treatment group (P < 0.05). Moreover, both insecticides exerted stress effects on A. glycines, and specimens treated with the two insecticides at the LC50 showed a significant decrease in their growth rates relative to those treated with the insecticides at LC30. These results provide a reference for exploring the effects of imidacloprid and thiamethoxam on A. glycines population dynamics in the field and offer insight to agricultural producers on the potential of low-lethal concentrations of insecticides to stimulate insect reproduction during insecticide application.

Silica nanoparticles as pesticide against insects of different feeding types and their non-target attraction of predators.

The agricultural use of silica (SiO2) nanoparticles (NPs) has the potential to control insect pests while the safety and tritrophic effects on plants and beneficial natural enemies remains unknown. Here, we evaluate the effects of silica NPs on insect pests with different feeding niches, natural enemies, and a plant. Silica NPs were applied at different concentrations (75-425 mg/L) on field-cultivated faba bean and soybean for two growing seasons. The faba bean pests, the cowpea aphid Aphis craccivora and the American serpentine leafminer Liriomyza trifolii, and the soybean pest, the cotton leafworm Spodoptera littoralis, were monitored along with their associated predators. Additional laboratory experiments were performed to test the effects of silica NPs on the growth of faba bean seedlings and to determine whether the rove beetle Paederus fuscipes is attracted to cotton leafworm-infested soybean treated with silica NPs. In the field experiments, silica NPs reduced the populations of all three insect pests and their associated predators, including rove beetles, as the concentration of silica NPs increased. In soybean fields, however, the total number of predators initially increased after applying the lowest concentration. An olfactometer-based choice test found that rove beetles were more likely to move towards an herbivore-infested plant treated with silica NPs than to a water-treated control, suggesting that silica NPs enhance the attraction of natural enemies via herbivore-induced plant volatiles. In the laboratory, while silica NPs inhibited the development of faba bean roots at 400 mg/L, they did not affect germination percentage, germination time, shoot length, or vigor index compared to the control.

Simple Osthole/Nanocarrier Pesticide Efficiently Controls Both Pests and Diseases Fulfilling the Need of Green Production of Strawberry.

The application of botanical pesticides is a good choice in organic agriculture. However, most botanical pesticides have limitations of slow action and short persistence for pest and disease management, which constrain their further application. With the objective of exploring a green pesticide for controlling strawberry pests and diseases simultaneously, a star polymer (SPc) with a low production cost was synthesized as a pesticide nanocarrier through simple reactions. The SPc complexed with osthole quickly through electrostatic interaction and hydrophobic association, which decreased the particle size of osthole down to the nanoscale (17.66 nm). With the help of SPc, more nano-sized osthole was delivered into cytoplasm through endocytosis, leading to the enhanced cytotoxicity against insect cells. As a green botanical pesticide, the control efficacy of the osthole/SPc complex was improved against main strawberry pests (green peach aphid and two-spotted spider mite) and disease (powdery mildew), which fulfilled the need of both pest and disease management in sustainable production of strawberry. Meanwhile, the introduction of SPc not only improved plant-uptake but also decreased the residue of osthole due to the higher degradation rate. Furthermore, the application of the osthole/SPc complex exhibited no influence on the strawberry fruit quality and nontarget predators. To our knowledge, it is the first success to control plant pests and diseases simultaneously for sustainable agriculture by only one pesticidal formulation based on nanoparticle-delivered botanical pesticides.

Quercetin and Rutin as Modifiers of Aphid Probing Behavior.

Rutin and its aglycone quercetin occur in the fruits, leaves, seeds, and grains of many plant species and are involved in plant herbivore interactions. We studied the effect of the exogenous application of rutin and quercetin on the probing behavior (= stylet penetration activities in plant tissues) of Acyrthosiphon pisum on Pisum sativum, Myzus persicae on Brassica rapa ssp. pekinensis, and Rhopalosiphum padi on Avena sativa using the electrical penetration graph technique (EPG = electropenetrography). The reaction of aphids to quercetin and rutin and the potency of the effect depended on aphid species, the flavonol, and flavonol concentration. Quercetin promoted probing activities of A. pisum within non-phloem and phloem tissues, which was demonstrated in the longer duration of probes and a trend toward longer duration of sap ingestion, respectively. M. persicae reached phloem in a shorter time on quercetin-treated B. rapa than on the control. Rutin caused a delay in reaching sieve elements by A. pisum and deterred probing activities of M. persicae within non-phloem tissues. Probing of R. padi was not affected by quercetin or rutin. The potency of behavioral effects increased as the applied concentrations of flavonols increased. The prospects of using quercetin and rutin in plant protection are discussed.

Evaluation of Aphicidal Effect of Essential Oils and Their Synergistic Effect against Myzus persicae (Sulzer) (Hemiptera: Aphididae).

The insecticidal activities of essential oils obtained from black pepper, eucalyptus, rosemary, and tea tree and their binary combinations were investigated against the green peach aphid, Myzus persicae (Aphididae: Hemiptera), under laboratory and glasshouse conditions. All the tested essential oils significantly reduced and controlled the green peach aphid population and caused higher mortality. In this study, black pepper and tea tree pure essential oils were found to be an effective insecticide, with 80% mortality when used through contact application. However, for combinations of essential oils from black pepper + tea tree (BT) and rosemary + tea tree (RT) tested as contact treatment, the mortality was 98.33%. The essential oil combinations exhibited synergistic and additive interactions for insecticidal activities. The combination of black pepper + tea tree, eucalyptus + tea tree (ET), and tea tree + rosemary showed enhanced activity, with synergy rates of 3.24, 2.65, and 2.74, respectively. Essential oils formulation was effective on the mortality of aphids. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that stability of a mixture of essential oils was not affected by store temperature (15, 25, and 35 °C) and the functional groups were not changed during storage. Based on our results, the essential oils can be used as a commercial insecticide against M. persicae.

Characterization and Toxicity of Crude Toxins Produced by Cordyceps fumosorosea against Bemisia tabaci (Gennadius) and Aphis craccivora (Koch).

Cordyceps fumosorosea, an insect pathogenic fungus, produces different toxins/secondary metabolites which can act as pest control agents. This study reports the extraction and characterization of crude mycelial extracts of C. fumosorosea isolate SP502 along with their bio-efficacy against Bemisia tabaci and Aphis craccivora. Fourier transform infrared spectroscopy, liquid chromatography, mass spectrometery and nuclear magnetic resonance analysis of C. fumosorosea isolate SP502 extracts showed the presence of five major compounds-Trichodermin, 5-Methylmellein, Brevianamide F, Enniatin and Beauvericin-which all may potentially be involved in insecticidal activity. The HPLC analysis of C. fumosorosea mycelial extracts and Beauvericin standard showed similar chromatographic peaks, with the content of Beauvericin in the crude toxin being calculated as 0.66 mg/ml. The median lethal concentrations of C. fumosorosea mycelial extracts towards first, second, third and fourth instar nymphs of A. craccivora were 46.35, 54.55, 68.94, and 81.92 µg/mL, respectively. The median lethal concentrations of C. fumosorosea mycelial extracts towards first, second, third and fourth instar nymphs of B. tabaci were 62.67, 72.84, 77.40, and 94.40 µg/mL, respectively. Our results demonstrate that bioactive compounds produced by C. fumosorosea isolate SP502 have insecticidal properties and could, therefore, be developed into biopesticides for the management of B. tabaci and A. craccivora.

Exogenous salicylic acid improves resistance of aphid-susceptible wheat to the grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae).

Salicylic acid (SA), a phytohormone, has been considered to be a key regulator mediating plant defence against pathogens. It is still vague how SA activates plant defence against herbivores such as chewing and sucking pests. Here, we used an aphid-susceptible wheat variety to investigate Sitobion avenae response to SA-induced wheat plants, and the effects of exogenous SA on some defence enzymes and phenolics in the plant immune system. In SA-treated wheat seedlings, intrinsic rate of natural increase (rm), fecundity and apterous rate of S. avenae were 0.25, 31.4 nymphs/female and 64.4%, respectively, and significantly lower than that in the controls (P < 0.05). Moreover, the increased activities of phenylalanine-ammonia-lyase, polyphenol oxidase (PPO) and peroxidase in the SA-induced seedlings obviously depended on the sampling time, whereas activities of catalase and 4-coumarate:CoA ligase were suppressed significantly at 24, 48 and 72 h in comparison with the control. Dynamic levels of p-coumaric acid at 96 h, caffeic acid at 24 and 72 h and chlorogenic acid at 24, 48 and 96 h in wheat plants were significantly upregulated by exogenous SA application. Nevertheless, only caffeic acid content was positively correlated with PPO activity in SA-treated wheat seedlings (P = 0.031). These findings indicate that exogenous SA significantly enhanced the defence of aphid-susceptible wheat variety against aphids by regulating the plant immune system, and may prove a potential application of SA in aphid control.

Sublethal and lethal effects of the imidacloprid on the metabolic characteristics based on high-throughput non-targeted metabolomics in Aphis gossypii Glover.

Sublethal effect considered as an emerging factor to assess the environmental risk of insecticides, which can impact the insects on both physiology and behavior. Lethal exposure can be causing near immediate mortality. Pests are inevitably exposed to sublethal and lethal dose in the agroecosystem following application of pesticides. Insecticides, widely used for the control of insect pests, are irreplaceable in insect pest management. The effects of imidacloprid by the method of high-throughput non-targeted metabolomics was investigated in Aphis gossypii Glover exposed to LC10 and LC90 doses of the imidacloprid, and the control group was treated with the same condition without imidacloprid. Pairwise comparisons showed that 111 metabolites changed significantly, 60 in the LC10 group, and 66 in the LC90 group compared to the control group, while only 16 changes in the LC10 were same with that in LC90 group. Among the changed metabolites, a total of 16 metabolites were identified as potential biomarkers, which represented the most influential pathways including glycolysis and gluconeogenesis, alanine, aspartate, and glutamate metabolism, ascorbate and aldarate metabolism, glutathione metabolism, phenylalanine metabolism, tyrosine metabolism, caffeine metabolism and parkinson's disease (PD), which could account for the sublethal and lethal effects on A. gossypii. These modified metabolic pathways demonstrated that high energy consumption, excitotoxicity and oxidative stress (OS) were appeared in both LC10 and LC90 groups, while PD was detected only in the LC90 group. The results of non-targeted metabolomics revealed the effects of neonicotinoid pesticide exposure on A. gossypii successfully, and provided a deep insight into the influenced physiology by the stress of neonicotinoid pesticide in the insect.

Aphid endosymbiont facilitates virus transmission by modulating the volatile profile of host plants.

BACKGROUND: Most plant viruses rely on vectors for their transmission and spread. One of the outstanding biological questions concerning the vector-pathogen-symbiont multi-trophic interactions is the potential involvement of vector symbionts in the virus transmission process. Here, we used a multi-factorial system containing a non-persistent plant virus, cucumber mosaic virus (CMV), its primary vector, green peach aphid, Myzus persicae, and the obligate endosymbiont, Buchnera aphidicola to explore this uncharted territory. RESULTS: Based on our preliminary research, we hypothesized that aphid endosymbiont B. aphidicola can facilitate CMV transmission by modulating plant volatile profiles. Gene expression analyses demonstrated that CMV infection reduced B. aphidicola abundance in M. persicae, in which lower abundance of B. aphidicola was associated with a preference shift in aphids from infected to healthy plants. Volatile profile analyses confirmed that feeding by aphids with lower B. aphidicola titers reduced the production of attractants, while increased the emission of deterrents. As a result, M. persicae changed their feeding preference from infected to healthy plants. CONCLUSIONS: We conclude that CMV infection reduces the B. aphidicola abundance in M. persicae. When viruliferous aphids feed on host plants, dynamic changes in obligate symbionts lead to a shift in plant volatiles from attraction to avoidance, thereby switching insect vector's feeding preference from infected to healthy plants.

Extracts of native forest species of the southern amazon in the control of Aphis craccivora koch (Hemiptera: aphididae)

The objective of this study was to evaluate the mortality of Aphis craccivora Koch (Hemiptera: Aphididae) submitted to different extracts with different concentrations of leaves of the native forest species: Tetragastris altissima (Aubl.) Swart (Burseraceae), Metrodorea flavida K. Krause (Rutaceae) and Cheiloclinium cognatum (Miers) AC Sm (Celastraceae) under laboratory conditions. Adults of Aphis craccivora were collected in Gliricidia sepium (Jacq.) Kunthe Walp. (Fabaceae), and separated into groups of ten individuals, transferred to Petri dishes and exposed to topical application of aqueous, alcoholic and leaf infusion extracts of Cheiloclinium cognatum, Metrodorea flavida and Tetragastris altissima. The extracts were applied at concentrations of: 3, 6, 9, 12 and 15%, with 1% dimethylsulfoxide (DMSO), using a control treatment 1 (distilled water + DMSO 1%) and control treatment 2 (fipronil). Evaluations were performed at 24, 48 and 72 hours after the application of the extracts by counting the dead insects. The experimental design was completely randomized, with five replicates, three types of extracts and five concentrations with controls. In all the studied species, the aqueous and infusion extracts presented a lower mortality (less than 52%), whereas the alcoholic extract in higher concentrations of Cheiloclinium cognatum, Metrodorea flavida showed a mortality of up to 100%. The species Tetragastris altissima reached an average mortality of 92%. The lethal concentration for the alcoholic extract of Cheiloclinium cognatum was LC50 6.43% and LC90 12.22%, Metrodorea flavida LC50 was 3.08% and LC90 7.05% and that for Tetragastris altissima LC50 5.58% and LC90 17.47%, after 72 hours. The use of the alcoholic extract of the species Metrodorea flavida at a concentration of 9% in the control of Aphis craccivora is indicated.

Relationship between imidacloprid residues and control effect on cotton aphids in arid region.

In this case, the dissipation and residues of imidacloprid as well as its control efficacy against aphids (Aphis gossypii Glover) in cotton cropping system were reported. After the final spray at the rates of 10.5-42.5 g a.i. ha-1, the initial deposits were 0.59-2.25 mg kg-1 with half-lives of 2.12-2.84 days on leaves and 0.06-0.21 mg kg-1 with half-lives of 1.51-4.20 days in soil, respectively. The initial residues were significantly higher with longer persistence in the upper position of the leaf than in middle and lower positions. The different application dosages could induce a significant difference in the initial deposits, but not show consistent correlation with the dissipation rate. The repeated applications of imidacloprid could alter its residue levels and dissipation rates. The long-term residue concentrations of imidacloprid (60 days after the final application) reached to the nondetectable level in soil. Combined with the control efficacy results, it was considered that the recommended dose of imidacloprid on cotton could be used effectively and safe in this arid area from the view of crop protection and environmental contamination.

Comparison between sustained effects of spray and injection thiamethoxam on apple aphids and non-target insects in apple orchard.

Spray application is considered to be the most common method of insecticide use in apple orchard, while trunk injection has often be used in labor-intensive areas. Here, a comparison of both methods in aphid control efficiency and non-target effects was conducted. We evaluated the effects of thiamethoxam by either spray or injection on apple aphid Aphis citricola, and examined the temporal dynamic of thiamethoxam in leaves by using residue analysis. Results showed that thiamethoxam had a remarkable suppression effect on Aphis citricola, and both application methods had obvious control efficiency with the highest value above 90%. The control effect of spray method on Aphis citricola reached the maximum at 7 days after application, while that of injection method reached the maximum at 14 days after application. Moreover, the control effect of injection after 14 days and that of spray after 7 days were not significant, suggesting the spray method had a higher quick-acting effect than the injection method, and the two methods had a similar persistence effect. The population dynamics of non-target insects (ladybugs, parasitoid wasps and predatory bugs) showed basically the same as that of blank controlled. The control effect evaluation of thiamethoxam on Aphis citricola suggest that injection treatment was more effective in protecting natural enemies than spray treatment, and thiamethoxam didn't interfere with natural enemies to control Aphis citricola with both two application methods.

Design and synthesis of novel hydrocarbylidene nitrohydrazinecarboximidamides against aphids based on natural product galegine.

A series of novel hydrocarbylidene nitrohydrazinecarboximidamides were designed and synthesized using an insecticidal natural product Galegine as a lead compound. The bioassay results show that the target compounds exhibited moderate to good insecticidal activities against Hyalopterus pruni Geoffroy at a concentration of 200 mg/L, and most compounds show excellet insecticidal activities against Aphis gossypii Glover. In particular, compounds IIc-01, IIc-03, IIe-02 and IIf-01 show the equal activities to a commercial pesticide Imidacloprid with their LC50 values are 0.21 mg/L, 0.27 mg/L, 0.12 mg/L and 0.24 mg/L, respectively, and compounds IIc-02 and IIe-05 show 10 times insecticidal activities as much as Imidacloprid with their LC50 values both are 0.02 mg/L. Structure-activity relationship and 3D-QSAR analyses indicate that the introduction of fluorine atom is useful for increasing the insecticidal activity of target compounds.