Synthesis of new distyrylpyridine analogues bearing amide substructure as effective insecticidal agents

In examining for unique insecticidal agents, two derivatives namely, 2-((3-cyano-4,6-distyrylpyridin-2-yl)thio)-N-(4-nitrophenyl)acetamide (2) and 3-amino-N-(4-nitrophenyl)-4,6-distyrylthieno[2,3-b]pyridine-2-carboxamide (3) were synthesized from distyrylpyridine-2-thione (1). The new compounds were structurally clarified by spectral and elemental analysis data. The insecticidal activity of these compounds were carried out against cowpea aphid, Aphis craccivora Koch. It is demonstrated that the compounds 2 and 3 have noteworthy insecticidal activity against nymphs of cowpea aphid with LC50 values of 0.025-0.027 ppm and 0.005-0.006 ppm after 24 h and 48 h of treatment, respectively. Also, the compounds 2 and 3 have noteworthy insecticidal activity against adults of cowpea aphid with LC50 values of 0.112-0.129 ppm and 0.014-0.015 ppm after 24 h and 48 h of treatment, respectively, that were comparable to that of the control acetamiprid.

The Fungus Metarhizium sp. BCC 4849 Is an Effective and Safe Mycoinsecticide for the Management of Spider Mites and Other Insect Pests

Five isolates of Metarhizium sp. were evaluated for their pathogenicity against the spider mite (Tetranychus truncatus Ehara) (Acari: Tetranychidae) and Metarhizium sp. BCC 4849 resulted in the highest mortality (82%) on the 5th day post-inoculation (DPI). Subsequent insect bioassay data indicated similar high virulence against five other insects: African red mites (Eutetranychus africanus Tucker) (Acari: Tetranychidae), bean aphid (Aphis craccivora Koch) (Hemiptera: Aphididae), cassava mealybug (Phenacoccus manihoti Matile-Ferrero) (Hemiptera: Pseudococcidae), sweet potato weevil (Cylas formicarius Fabricius) (Coleoptera: Brentidae), and oriental fruit fly (Bactrocera dorsalis Hendel) (Diptera: Tephritidae), at mortalities of 92–99%, on 3rd–6th DPI, and in laboratory conditions. The pathogenicity assay against E. africanus in hemp plants under greenhouse conditions indicated 85–100% insect mortality on 10th DPI using the fungus alone or in combination with synthetic acaricide. Genome sequencing of Metarhizium sp. BCC 4849 revealed the high abundance of proteins associated with zinc-, heme-, and iron-binding; oxidation-reduction; and transmembrane transport, implicating its versatile mode of interaction with the environment and adaptation to various ion homeostasis. The light and scanning electron microscopy indicated that at 24 h post inoculation (PI), adhesion and appressorial formation occurred, notably near the setae. Most infected mites had stopped moving and started dying by 48–72 h PI. Elongated hyphal bodies and oval blastospores were detected in the legs. At 96–120 h PI or longer, dense mycelia and conidial mass had colonized the interior and exterior of dead mites, primarily at the bottom than the upper part. The shelf-life study also indicated that conidial formulation combined with an oxygen-moisture absorber markedly enhanced the viability and germination after storage at 35 °C for four months. The fungus was tested as safe for humans and animals, according to our toxicological assays.

Comparative Functional and Numeric Response of Two Coccinellids (Coccinella septempunctata and Cheilomenes sexmaculata) Preying Cowpea Aphid (Aphis craccivora)

Background: The cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae), a plant lice known to commonly attack plants that causes loss by sucking sap from phloem and act as vector for viruses. The aphidophagous coccinellids are efficient in controlling the pestiferous population of aphids. The two coccinellid Coccinella septempunctata and Cheilomenes sexmaculata are efficient in predation of cowpea aphid, Aphis craccivora in southern Rajasthan. The present study determined the response of prey consumption at different prey densities. Methods: To compute the functional and numeric response of the lady bird beetle on cowpea aphid, experiment was conducted in vitro by using cowpea potted plant in caged conditions at Department of Entomology, Rajasthan College of Agriculture during 2019-20. The cowpea pea plants were sown in small pots and were placed in aluminium insect cages having 15 cm × 15 cm × 15 cm size. The predatory potential of coccinellid grubs and adults were evaluated at six different prey densities (aphids per arena): 25, 50, 75, 100, 125, 150 and 200 with 5 replications. Result: The grub and adults of C. septempunctata consumed more prey as compared to C. sexmaculata. Both the coccinellid showed Type II functional response when functional curve was plotted. The linear regression method suggested that C. septempunctata required less time to act upon prey as compared to C. sexmaculata. The C. septempunctata also showed more numeric response in terms of ECI [conversion efficiency of prey consumption (ECI) into biomass (egg)] at different prey densities. The fecundity in both the cases increased with the increased prey densities that eventually decreased after reaching the maximum egg laying capacity at prey density of 125 aphids. In all the cases it was found that consumption rate of predaceous beetle increased with increasing aphid population.

Diversity of Insect Pests and Ecofriendly Fauna Inhabiting Chickpea (Cicer arietinum L.) Agro-Ecosystem in Bundelkhand Region of Uttar Pradesh

An experiment was conducted at Agricultural Research Farm of Brahmanand Post Graduate College, Rath, Hamirpur (U.P.) during 2016-17 and 2019-20 cropping season. In the Bundelkhand agro climatic region seventeen species of insect belonging to seven orders and twelve families were recorded from chickpea agro ecosystem. Among which six species from Lepidoptera, four species from hymenoptera, two species from coleoptera and odonata and one species from hemiptera, isoptera, and dyctyoptera were identified. On the basis of economic importance nine species were insect pests, five species were predators, two species were insect parasitoids and one species was insect pollinator. Among the nine species of insect pests, chickpea pod borer, Helicoverpa armigera Hub. and gram cut worm, Agrotis ipsilon (Huf.) occurred regularly and chickpea pod borer was designated as a major pest while, gram cut worm infested with very low population density and considered as minor insect pest of chickpea. The five species of insect pest occurred occasionally i.e. armyworm, Mythmina separate (walker), tobacco caterpillar, Spodoptera litura (Fab), cow pea aphid, Aphis craccivora (Koch), termite, Odentotermes obesus (Rambur) and black flea beetle, Altica Species (unidentified species) were designated as minor pest of chickpea. While, two species namely, Bihar hairy caterpillar, Spilarctia obliqua (Walker) and beet armyworm, Spodoptera oxiqua (Hub) occurred intermittently in sporadic manner and designated as stray pest of chickpea. The eight species of insect’s ecofriendly fauna inhabiting chickpea agro ecosystem were observed, among which five species of predators, two species of parasitoids and one species of pollinators foraged on chickpea crop occasionally in very low population density. The maximum number of ecofriendly fauna was of the order hymenoptera, two species of parasitoids, one species of predators and pollinator i.e. Trichogrammatid wasp, Trichogramma chilonis (Ishii), ichneumonid wasp, Campoletis chloridae (Uchida), common yellow wasp, Vespa oreintalis (L.) and small honeybee, Apis floraea followed by odonata i.e. dragonfly, Croccothemis servielia (Drury) and damsel fly, Agriocnemis pygmiea (Rambur), coleoptera, rove beetle, Alleochara billienata and dyctyoptera, praying mantis, Mantis religiosa (L.).

Potency of Three Botanical Oils Against the Aphis Craccivora Koch (Homoptera: Aphididae) Nymphs Under Laboratory Conditions

Botanicals are promising and attractive alternatives for pest management. In the present study, three botanical oils namely neem (Azadirachta indica), karanja (Pongamia pinnata) and mehogony (Swietenia mahagoni) were tested against the nymphs of Aphis craccivora Koch to evaluate the toxic and repellent effects under laboratory conditions (25 ± 5oC, 65-75% RH). Four concentrations (0.5, 1.0, 1.5, and 2.0%) along with control were maintained with distilled water and tween-20 was used as emulsifier. Leaf dipped method were used for insect bioassay. Insect mortality was recorded at 24, 48 and 72 hours after intervals while repellency was carried out at 2 hours after intervals upto 10th hours and the collected data were analyzed through MSTAT-C program. Results indicated that all the tested oils had toxic and repellent effects against the A. craccivora nymphs. Among the tested botanical oils, no significant difference was observed in terms of mortality over treatment time. But significant difference was noticed over level of concentrations exerted by the botanical oils. The average highest mortality (28.62%) was recorded by the application of mehogony oil whereas neem oil showed the lowest mortality (27.21%) against the A. craccivora and the mortality was directly proportional to the level of concentrations and hour after treatment (HAT). Probit analysis showed the lowest LD50 values of mehogony oil which revealed the highest toxic effect against the nymph of bean aphid. The highest repellent effect (77.33%) was found in mehogony oil (repellent class IV) among all the botanical oils applied. On the contrary, neem (57.33%) and karanja (55.00%) oils belonged to the same repellent class that is repellent class II. Although all the tested botanical oils evaluated showed toxic and repellent effects but mehogony oil performed as the best potent oil against the nymphs. We therefore suggested using the mehogony oil for the management of bean aphid. SAARC J. Agric., 19(1): 139-154 (2021)

Evaluation of Developmental and Reproductive Fitness of Laboratory Selected Thiamethoxam Resistance in Black Legume Aphid Aphis craccivora Koch.

Thiamethoxam is a neonicotinoid group of insecticide which are selective agonists of the insect nicotinic acetylcholine receptor (nAChR), a pentameric cys-loop ligand-gated ion channel located in the central nervous system of insects. They provide farmers with invaluable, highly effective tools against some of the world’s most destructive crop pests. Black legume aphids, Aphis craccivora is one of the devastating polyphagous pests in agroecosystem and to manage their population, farmers are still relying on application of synthetic insecticides like Thiamethoxam. To evaluate the risk of resistance development, selection of A. craccivora was done to characterize Thiamethoxam resistance along with evaluation of developmental and reproductive fitness cost of the resistance. About 86.19 folds of resistance were developed after selecting for 24 generations. In the first twelve generations steady development of resistance was noticed followed by development become stiffer till 16th generation and more or less stable till 24th generations. Relative fitness of the selected resistant strain of aphids was decreased with longer nymphal duration and adult longevity. The mean nymphal duration was increased from 4.35±1.02 days (in F0) to 7.9±0.57 days (in F24). The fecundity rate was significantly less in resistant population (16.0±5.34) as compared to the susceptible strain (54.71±7.63) whereas, oviposition periods were significantly longer (12.49±1.44 days) in resistant population as compare to susceptible strain (9.50±1.22 days).

Entomopathogenic Fungi on Fabae bean Aphid, Aphis craccivora (Koch) (Hemiptera: Aphididae)

The Aphids, Aphis craccivora (Koch) is a serious pest in agricultural fields in Egypt. Entomopathogenic fungi are biological control agents of insects. The study was carried out on the aphid by using of Bio Catch, Verticillium lecanii, Bio Power, Beauveria bassiana and Bio Magic, Metarhizium anisopliae on A. craccivora. Laboratory experiments were done to measure the pathogenicity of three commercial compounds from entomopathogenic fungi, Bio Catch, V. lecanii, Bio Power, B. bassiana, and Bio Magic, M. anisopliae against adults and nymphs of A. craccivora. Three concentrations were used from all compounds, 107 , 108 and 109 spores/ml. at 22 ± 2°C and 75 ± 5 R.H. The concentration (109 spores/ml.) gave 100% mortality with V. lecanii and B. bassiana then M. anisopliae. The Lowest LC50 value of 2.1 x 106 spores/ml. was recorded by V. lecanii, which showed higher virulence compared to other entomopathogenic fungi. The LC50 values of V. lecanii, B. bassiana and M. anisopliae were 2.1 x 106 , 4.3 x 106 and 6.4 x 107 spores ml., respectively. At the highest concentration of 109 spores/ml., the Median LT50 values for V. lecanii, B. bassiana and M. anisopliae were 4.2, 5.2 and 7.0 days, respectively.

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.