Leaf Dip Method Research Articles

Broflanilide effectively controls Helicoverpa armigera and Spodoptera exigua exhibiting diverse susceptibilities to chlorantraniliprole and emamectin benzoate.

The cotton bollworm, Helicoverpa armigera (Hübner), and the beet armyworm, Spodoptera exigua (Hübner), are two major polyphagous lepidopteran pests of cultivated crops. They develop various levels of resistance to many frequently applied broad-spectrum insecticides. Here, the larval susceptibilities of a laboratory population and six field-collected populations per pest from Hunan Province, China to three insecticides were determined using a standard leaf-dipping method in the laboratory. Field-plot trials were conducted to verify the control efficacies of broflanilide 100 g L-1 suspension concentrate (SC), chlorantraniliprole 5% SC and emamectin benzoate 5.7% water-dispersible granule, against H. armigera and S. exigua larvae using foliar sprays in 2013 and 2019. Variations among H. armigera and S. exigua field populations in their susceptibility levels to the three insecticides were observed in Linli, Yueyang and Changsha counties from 2013 to 2019. They were still high susceptibility to broflanilide only, but developed low and/or moderate levels of resistance to chlorantraniliprole and emamectin benzoate. In addition, broflanilide at 25 g ha-1 provided an excellent control efficacy of 81.92% to 96.46% against these pests during the 3-14-days period after treatment in both years, whereas chlorantraniliprole at 50 g ha-1 and emamectin benzoate at 4.5 g ha-1 exhibited significantly decreased efficacies, which were consistent with their corresponding toxicity levels. These results suggest that broflanilide should be an important new tool for the effective control of diamide- and avermectin-resistant H. armigera and S. exigua. © 2020 Society of Chemical Industry.

Millettia pinnata and Sesamum indicum seed oil based green pesticide formulations for the management of tea red spider mite, Oligonychus coffeae Nietner (Acari: Tetranychidae)

Red spider mite, Oligonychus coffeae is an economically important pest of tea in major tea producing countries. The present study aimed to evaluate the efficacy of five plant oil based formulations viz.., SOF, MOF, SMOF1:1, SMOF3:2 and SMOF2:3 prepared by considering individual as well as combination of Sesamum indicum and Millettia pinnata seed oil at different ratios of 1:0, 0:1, 1:1, 3:2 and 2:3, respectively against eggs and adults stages of O. coffeae. The experiments were done following leaf dip and direct spray methods. LC50 values of different formulations viz.., SOF, MOF, SMOF1:1, SMOF3:2 and SMOF2:3 against O. coffeae (adult females) were 3807.10 ppm, 4672.88, 3248.98, 4155.57 and 4610.55 ppm, respectively. The formulations also showed significant ovicidal and growth inhibitory activity against O. coffeae. Two season field bio-efficacy results indicated that the formulations are highly effective against O. coffeae and were superior to commonly used chemical acaricide, ethion 50EC. No phytotoxic symptoms were observed on tea leaves treated with these formulations. Black tea manufactured from tea shoots treated with these oil formulations were free from any taint and scored good (6–8 in 10 scale) in organoleptic test. The data suggests that plant oils of M. pinnata and S. indicum seeds alone and in combinations have potential to manage tea red spider mite in the field and can be recommended for eco-friendly management of mite pest in tea.

Synthesis and Insecticidal Activity Evaluation of Virtually Screened Phenylsulfonamides.

The fastest and most effective way to control pests is to use pesticides. However, with the accumulation of pesticide resistance and the difficulties of rapidly producing new pesticides, it is of great significance to create new pesticides through new synthetic methods. In this study, we report a computer-aided drug design (CADD)-assisted method to obtain two lead sulfonamides by homology modeling and virtual screening. On this basis, the lead compounds were synthesized from p-chlorocresol by four steps of esterification, sulfonation, sulfonamidation, and amidation. Further, 71 derivatives were synthesized by optimizing the lead compounds, and their insecticidal activities against Mythimna separata were evaluated by the leaf-dipping method. Notably, seven sulfonamides (5a, 5g, 5h, 5m, 6b, 6g, and 6m) with excellent insecticidal activity were obtained, and the possible binding modes between receptors and active groups in sulfonamides were verified by structure-activity relationship and docking simulation, which provided theoretical support for the subsequent development of these novel candidate insecticides.

Contrasting susceptibility of lepidopteran pests to diamide and pyrethroid insecticides in a region of overwintering and migratory intersection.

Pesticide resistance is a growing issue worldwide, and susceptibility of pest populations should be monitored in migratory intersection regions for successful resistance management. We determined the susceptibility of eight noctuid species from the Florida Panhandle to bifenthrin (pyrethroid) and chlorantraniliprole (diamide). Larvae from field and laboratory populations were exposed to commercial insecticide formulations using the leaf-dip method in concentration-mortality bioassays. The field populations of Helicoverpa zea (Boddie), Spodoptera frugiperda (Smith), S. eridania (Stoll), S. exigua (Hubner) and Chloridea virescens (Fabricius) had reduced susceptibility to bifenthrin compared with the laboratory populations. Resistance ratios to bifenthrin were as high as 10 071-fold in S. exigua and 436-fold in S. frugiperda, while there was no reduced susceptibility in Agrotis ipsilon (Hufnagel). The susceptibility to chlorantraniliprole was similar between the field and laboratory populations studied, except for S. exigua that exhibited 630-fold resistance to the diamide. The probit regression equations indicated that the larval mortality of S. exigua and S. frugiperda populations was <80% with bifenthrin at the concentration equivalent to the label rate. Likewise, the estimated mortality of S. exigua larvae with chlorantraniliprole at the label rate concentration was <80%. The lepidopteran pest populations tested were variable in susceptibility to bifenthrin by contrast to more consistent susceptibility to chlorantraniliprole. These results help in the choice of effective insecticides for integrated pest management and resistance management in cropping systems colonized by migratory lepidopteran pests from the U.S. Gulf Coast region. © 2020 Society of Chemical Industry.

Toxicity of Insecticides on Thrips palmi Karny and Thrips tabaci Lindeman (Thysanoptera: Thripidae) in Osaka Prefecture, Japan

We determined the toxicity of insecticides by using the leaf-dipping method on two thrips species, Thrips palmi and Thrips tabaci. They were collected from 3 populations in Osaka Prefecture in 2017 and 2019, and the effects of 11 and 7 insecticides, respectively, for the two species were examined. The most effective insecticides against T. palmi were emamectin benzoate, fluxametamide, and flometoquin, whereas MEP and thiocyclam were effective against T. tabaci.

Combinatorial Synthesis of A Series of Paeonol-based Phenylsulfonyl hydrazone Derivatives as Insecticidal Agents.

Plant secondary metabolites play an essential role in the discovery of novel insecticide due to their unique sources and potential target sites. Paeonol, the main phenolic components in Moutan Cortex, is recognized as a safe and potent botanical insecticide to many insects. The structural modification of paeonol in this study into phenylsulfonylhydrazone derivatives is proved an effective approach for the development of novel insecticides, those derivatives being more toxic than paeonol. However, there have been no reports on the insecticidal activity of paeonol-based phenylsulfonylhydrazone derivatives in controlling Mythimna separata. We have been working to discover biorational natural products-based insecticides. Twelve novel paeonol-based phenylsulfonylhydrazone derivatives have been successfully prepared by structural modification of paeonol, and the insecticidal activity against M. separata by the leafdipping method at the concentration of 1 mg/mL has been evaluated. Insecticidal activity revealed that out of 12 title compounds, derivatives 5c and 5f displayed the best against M. separate with the FMR both of 53.6% than toosendanin (FMR = 50.0%). The results suggested that for the paeonol-based phenylsulfonylhydrazone series derivatives, the proper substituent of arylsulfonyl R at the hydroxyl position of paeonol was very important for their insecticidal activity. These preliminary results will pave the way for further modification of paeonol in the development of potential new insecticides.

Assessment of LC50 value of deltamethrin 2.8 EC, cypermethrin 25 EC, endosulfan 35 EC against Spilosoma obliqua Walker

The toxicity of some insecticides viz., deltamethrin, cypermethrin and endosulfan were determined against same age larvae (7 day old) of Spilosoma obliqua by leaf dip method at different concentrations 0.2, 0.02, and 0.002 percent for deltamethrin 2.8 EC, 0.4 0.04 and 0.004 for cypermethrin 25 EC and 08, .04 and .01 for endosulfan 35 EC. Deltamethrin proved to be the most toxic and quick acting insecticide amongst all the insecticide followed by cypermethrin and endosulfan during observation at12, 24, 48 and 72h after feeding . On the basis of LC50 values at different time intervals the order of toxicity was, deltamethrin > cypermethrin > endosulfan. These findings can be helpful for the selection of suitable insecticides for effective pest management under field condition.

Combinatorial Synthesis of Novel 9R-Acyloxyquinine Derivatives as Insecticidal Agents.

It is one of the effective ways for pesticide innovation to develop new insecticides from natural products as lead compounds. Quinine, the main alkaloid in the bark of cinchona tree as well as in plants in the same genus, is recognized as a safe and potent botanical insecticide to many insects. The structural modification of quinine into 9R-acyloxyquinine derivatives is a potential approach for the development of novel insecticides, which showed more toxicity than quinine. However, there are no reports on the insecticidal activity of 9Racyloxyquinine derivatives to control Mythimna separata. Endeavor to discover biorational natural products-based insecticides, 20 novel 9Racyloxyquinine derivatives were prepared and assessed for their insecticidal activity against M. separata in vivo by the leaf-dipping method at 1 mg/mL. Among all the compounds, especially derivatives 5i, 5k and 5t exhibited the best insecticidal activity with final mortality rates of 50.0%, 57.1%, and 53.6%, respectively. Overall, a free 9-hydroxyl group is not a prerequisite for insecticidal activity and C9- substitution is well tolerated; modification of out-ring double-bond is acceptable, and hydrogenation of double-bond enhances insecticidal activity; Quinine ring is essential and open of it is not acceptable. These preliminary results will pave the way for further modification of quinine in the development of potential new insecticides.

Biocontrol Potential of Some Entomopathogenic Fungal Strains Against Bean Aphid Megoura japonica (Matsumura)

This research reported the in vitro pathogenicity of Verticillium lecanii strains, L2 and L5, and Beauveria bassiana strains, B76 and B252, against Megoura japonica using leaf-dip method. The virulence potential of these four entomopathogenic fungal strains of V. lecanii and of B. bassiana were compared between fungi conidia (concentrations 1 × 106, 1 × 107, and 1 × 108 conidia mL−1) and culture filtrate. Moreover, binary combination of four different fungal strains (L2 + B76, B76 + L5, L2 + B252, and L2 + B76 + B252 + L5) were evaluated against M. japonica under control condition. Aphid mortality was recorded after two, four, six, and eight days of post-treatment. In the conidial concentration bioassay, strain B76 showed maximal mortality (85.3%) against bean aphid, and strain L5 showed the lowest effect (60.0%) at the highest concentration (1 × 108 conidia mL−1) at eight days post-treatment. Whereas, binary combinations of B76 and L2 strains showed the highest effect against M. japonica (90.5%) than other combinations. Moreover, in comparison with the effect of filtrate and conidia bioassay, 91.4% and 84.1% were achieved in strain B76, and the lowest effect (63.8% and 55.1%) was recorded in strain L5.

Synthesis of Novel (9S)-Acyloxy Derivatives of Quinidine and Dihydroquinidine as Insecticidal Agents.

Endeavor to discover biorational natural products-based insecticides, two series (30) of novel (9S)-acyloxy derivatives of quinidine and dihydroquinidine were prepared and assessed for their insecticidal activity against Mythimna separata in vivo by the leaf-dipping method at 1 mg/mL. Among all the compounds, especially four derivatives exhibited the best insecticidal activity with final mortality rates of 71.4 %, 75.0 %, 71.4 %, and 75.0 %, respectively. Relatively speaking, 9-hydroxy group is well tolerated, and the results showed that after modification of the hydroxy group with an acyloxy group, the insecticidal activity was significantly increased; the configuration at C8/9 position is important for insecticidal activity, and the (9S)-configuration is optimal; modification of the out-ring double bond is acceptable, and hydrogenation of the double bond enhances insecticidal activity. These preliminary results will pave the way for further modification of quinidine in the development of potential new insecticides.

Effect of different plant extracts on growth indices of tobacco caterpillar (Spodoptera litura) on soybean under laboratory conditions

Spodoptera litura (F.) is a polyphagous insect among which soybean is one of its hosts. Six different botanicalsi.e., three plant extracts (Datura leaf extract, Marigold leaf extract and Annona leaf extract) and three plant oils (Neem oil, Eucalyptus oil and Karanj oil) were used by preparing 5% aqueous solutions. Soybean leaves were treated with botanicals by leaf dip method and fed to prestarved second instar larvae and further studied their growth indices. The results indicated that Eucalyptus oil showed least larval index (0.45 in 3rd instar, 0.47 in 4th instar, 0.58 in 5th instar, 0.51 in 6th instar and 0.61 in pre-pupa), pupal index (0.44), adult index (only in case of males as 0.52) and lowest oviposition index (0.20). While, neem oil showed least adult index in females (0.82) and lowest total growth index (2.29).

Semi-Synthesis of C-Ring Cyclopropyl Analogues of Fraxinellone and Their Insecticidal Activity Against Mythimna separata Walker.

Fraxinellone (1) is a naturally occurring degraded limonoid isolated from Meliaceae and Rutaceae plants. As a potential natural-product-based insecticidal agent, fraxinellone has been structurally modified to improve its activity. Furan ring of fraxinellone is critical in exhibiting its insecticidal activity, but with few modifications. Herein, C-ring-modified cyclopropyl analogues were semi-synthesized by Rh(II)-catalyzed cyclopropanation. The structures of the target compounds were well characterized by NMR and HRMS. The precise three-dimensional structural information of 3a was established by X-ray crystallography. Their insecticidal activity was evaluated against Mythimna separata Walker by a leaf-dipping method. Compound 3c exhibited stronger insecticidal activity than 1 and toosendanin against M. separata with teratogenic symptoms during the different periods, implying that cyclopropanation of the furan ring could strengthen the insecticidal activity of fraxinellone.

Efficacy of Biorational Compounds against Mustard Aphid (Lipaphis erysimi Kalt.) and English Grain Aphid (Sitobion avenae Fab.) under Laboratory Conditions in Nepal

Mustard aphid (Lipaphis erysimi) and English grain aphid (Sitobion avenae) are among the most important pests in mustard and wheat fields in Nepal. Biocide Manic (Metarhizium anisopliae a.i. = 1 × 109 spores/ml) at 3 ml/l water, Agri Sakti (Beauveria bassiana a.i. = 1 × 109 spores/ml) at 3.3 ml/l water, Varunastra (Verticillium lecanii spores 2% aqueous suspension, 2 × 108 CFU/ml) at 6 ml/l water, Mahastra (Bacillus thuringiensis var. kurstaki 0.5% wettable powder) at 6 g/l water, Neemraj Super (Azadirachitin 0.3% w/w) at 3.3 ml/l water, Tracer (Spinosad 90% spinosyns) at 0.33 ml/l water, and control treatment (pure water) were used to test their efficacy against L. erysimi and S. avenae, using leaf dip and spray methods under laboratory conditions in Rupandehi, Nepal, in the year 2018. Each treatment was replicated four times, and the experiment was carried out in a randomized complete block design. Mortality of aphids was recorded at 24, 48, 72, and 98 hours after treatment application. The result revealed highest mortality of mustard aphids with Agri Sakti at 24 hours after treatment (HAT); however, Neemraj Super was found to be the most effective at 48, 72, and 96 HAT with the leaf spray method. With the leaf dip method, Neemraj Super killed more mustard aphids than other treatments at all observed time points. Among tested biorational products, Agri Sakti was found to be most effective against English grain aphids in both leaf spray and leaf dip methods. In all the bioassays, the mortality caused by biorational compounds over control was highly significant. The present study suggests for further verification of the biorational products in the field and development of novel management strategies against different species of aphids.

Synthesis of novel 9R/S-acyloxy derivatives of cinchonidine and cinchonine as insecticidal agents

Endeavor to discover biorational natural products-based insecticides, two series (27) of novel 9R/S-acyloxy derivatives of cinchonidine and cinchonine were prepared and assessed for their insecticidal activity against Mythimna separata in vivo by the leaf-dipping method at 1 mg/mL. Among all the compounds, especially derivatives 6l and 6o exhibited the best insecticidal activity with final mortality rates of 75.0% and 71.4%, respectively. Overall, a free 9-hydroxyl group is not a prerequisite for insecticidal activity and C9-substitution is well tolerated; the configuration of C8/9 position is important for insecticidal activity, and 9S-configuration is optimal; 6’-OCH3 moiety is not necessary, removal of it is also acceptable.

Evaluation of some pesticides against the tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under laboratory conditions

The tomato borer, Tuta absoluta (Meyrick) is considered a devastating pest, particularly to the tomato Lycopersicon esculentum. The present study was carried out to determine the efficacy of five pesticides namely, indoxacarb, (abamectin+ thiamethoxam), emamectin benzoate, fipronil and imidacloprid against the 3rd larval instar of T. absoluta under laboratory conditions using the Leaf-dip method. The tested pesticides could be descendingly arranged as follows: emamectin benzoate, fipronil, (abamectin + thiamethoxam), indoxacarb and imidacloprid. The corresponding LC50 values after 72 h. were 0.07, 0.22, 0.28, 0.59 and 2.67 ppm, while LC90 values were 0.56, 3.25, 1.99, 4.69 and 30.29 ppm, respectively. It is clear that emamectin benzoate was the most toxic compound, whereas imidacloprid was the least toxic one. Results indicated that emamectin benzoate can be used as a good element in integrated management program to this pest.

Toxicity of some insecticides against Agrotis spp. infesting cabbage

Toxicity of seven insecticides viz., bifenthrin, chlorantraniliprole, cypermethrin, emamectin benzoate, flubendiamide, novaluron and spinosad was evaluated through leaf dip and topical methods of bioassay against third instar larvae of Agrotis ipsilon (Hufnagel) and A. segetum (Denis and Schiffermuller). Based on LC50 values, chlorantraniliprole was found the most effective against third instar larvae of A. ipsilon (0.0298 ppm) as well as A. segetum (0.0321 ppm) while cypermethrin was the least effective, with LC50 values of 31.0706 and 33.4636 ppm, respectively. On the basis of LD50, chlorantraniliprole was observed to be the most effective against third instar larvae of A. ipsilon (0.00086 μg a.i./larva) as well as A. segetum (0.00085 μg a.i./larva) while novaluron being the least effective with LD50 values 0.8382 and 0.7441 μg a.i./larva, respectively.

Efficacy and toxicity of insecticides to green peach aphid

Outbreaks of Myzus persicae (Sulzer) (Hemiptera: Aphididae) populations are not rare in Brassica crops in Pernambuco State (Brazil). The aim of the present study was to perform laboratory assessments in seven insecticide formulations against M. persicae. The direct spray and leaf dip methods were used in the experiment. M. persicae mortality rates were subjected to variance and Probit analyses. Based on the results, thiamethoxam + lambdacyhalothrin, thiamethoxam, lambda-cyhalothrin and thiamethoxam + chlorantraniliprole were the most efficient insecticides after 24-hour exposure, since they caused over 95% mortality through the direct spray method. LC50s ranged from 0.10 to 9.1 mg a.i./L in chlorfenapyr and chlorantraniliprole, respectively, in the leaf dip method. All insecticides were effective against M. persicae, except for chlorantraniliprole. Chlorfenapyr, lambda-cyhalothrin, pymetrozine and thiamethoxam + lambda-cyhalothrin were the most toxic to this aphid.

Design, Synthesis, Acaricidal Activities, and Structure-Activity Relationship Studies of Novel Oxazolines Containing Sulfonate Moieties.

With the ultimate goal of addressing pest-related constraints on global agricultural production, we used combination principles to design and synthesize 2,4-diphenyl-1,3-oxazolines containing a sulfonate moiety at the para-position of the 4-phenyl group. The target compounds, which have strong affinity for lipids and can be expected to traverse cell membranes, were characterized by 1H and 13C NMR spectroscopy and high-resolution mass spectrometry. Their activities against the larvae and eggs of carmine spider mites (Tetranychus cinnabarinus) were determined by a leaf-dipping method and compared with the activity of the commercial acaricide etoxazole. Most of the test compounds displayed good ovicidal and larvicidal activities. In particular, a tert-butylphenyl-substituent compound possessed better larvicidal activity (LC50 = 0.022 ± 0.009 mg/L) and ovicidal activity (0.044 ± 0.020 mg/L) than etoxazole (0.091 ± 0.051 and 0.095 ± 0.059 mg/L, respectively). Given its outstanding bioactivities, this compound deserves further attention as a pesticide candidate.

Resistance development in Cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) to insecticides from Organophosphate, Thiadiazines and Thiourea derivatives

Cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is a highly invasive pest of cotton and other economically important agri-horticultural crops, worldwide. Majority of the cotton growers rely on chemical insecticides to control this pest. Indiscriminate use of insecticides has lead to development of resistance against some insecticides in recent years. Aiming to investigate the resistance development in P. solenopsis to some of the commonly used insecticides, Phenacoccus solenopsis colonies were collected from infested plants of cotton from four different locations namely Yavatmal, Wardha, Amravati and Akola districts of Vidarbha region of Maharashtra, India. The mealybugs were cultured on potato spouts in the laboratory for one generation to eliminate intermittent field infection of natural enemies and bio-assayed by leaf dip method in the laboratory. Results of bioassay indicated very high (RF 378.29) level of resistance against Thiadiazines (buprofezin) in mealybug population collected from Amravati, whereas resistance was found negligible at other locations. Low to very low level of resistance was recorded against organophosphates (monocrotophos, chlorpyrifos, quinalphos and acephate) and Thiourea derivatives (diafenthiuron) from all the locations. The results of the present study provide valuable information regarding selection of appropriate insecticides as one of the components of integrated management of P. solenopsis.

Biochemical resistance to insecticide in Bemisia tabaci field population from Burkina Faso, West Africa

Insecticides are commonly used in greenhouses or fields to control Bemisia tabaci populations leading to rapid evolution of resistance that make treatments inefficient. This resistance can be mediated by molecular and/or biochemical mechanisms. Here, we propose to determine the detoxifying enzymes involved in B. tabaci resistance and to establish the relationship between the enzymatic activity and the values of Lethal Concentrations 50 (LC50). Susceptibility to deltamethrin, acetamiprid and chlorpyrifos-ethyl was assessed, using leaf dip method populations sampled from four (4) sites in Burkina Faso in 2017. Detoxifying enzymes activities including non-specific α-esterases, Para Nitro Phenyl Acetate esterases, oxidases (cytochrome P450) and Glutathione -S-Transferases (GSTs) were measured on single B. tabaci (N = 50) from each test locality and compared with the susceptible strain. In all sites, B. tabaci demonstrated multiple resistance phenotypes. Variation in detoxifying enzyme activities was observed within B. tabaci populations. Elevated levels of non-specific α esterase and GSTs were widespread, suggesting multiple resistance mechanisms occurred within B. tabaci populations from this country.