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.

Impact of a synthetic insecticide and plant extracts on Aphis craccivora (Hemiptera: Aphididae) and coccinellid species in common beans

Bean crop is attacked by several phytophagous insects, affecting its production and causing losses to farmers. Among the insects considered as bean crop pests, aphids can cause economic damage by continuously sucking the plant sap throughout crop development. Thus, this study aimed to evaluate the control of Aphis craccivora on bean crop with insecticides and its effect on the presence of ladybugs. The tested products were: 1) imidacloprid + bifenthrin; 2) neem extract; 3) d-limonene, and, as a control treatment, water was applied. Insect mortality and the presence of ladybugs were checked every three days until harvest. There was a reduction in the population of aphids after the application of the products for up to 27 days. The presence of ladybugs was higher in the control treatment than in the treatments with insecticides. Thus, the tested products were considered potential in the control of A. craccivora. However, they also negatively affected the presence of coccinellids.

Insecticidal and Enzyme Inhibition Activities of Leaf/bark Extracts, Fractions, Seed Oil and Isolated Compounds From Triadica Sebifera (L.) Small Against Aphis Craccivora Koch

Aphid, Aphis craccivora Koch (Hemiptera: Aphididae) is a major sap-sucking insect pest of leguminous crops and also transmit plant viruses leading to economic yield loss. Insecticidal activities of T. sebifera have not been reported against A. craccivora and other insect pests till date. In this study, residual toxicity of leaf/bark extracts, seed oil, fractions, isolated compounds and its combinations; synergistic activity of leaf/ bark extract with seed oil and its enzyme inhibition activities against A. craccivora was studied. Among extracts, ethanolic bark extract 80% (LC50=5115.98 mg L-1) was more effective against A. craccivora than other extracts. Among fractions, n-hexane fraction of leaf (LC50=425.73 mg L-1) and ethyl acetate fraction of bark (LC50=813.45mg L-1) was more effective. Among compounds, gallic acid was most effective (LC50=1303.68 mg L-1) than shikimic acid and quercetin (LC50=1725.09 and 1855.93 mg L-1, respectively). Seed oil (LC50=850.94 mg L-1) is more superior than extracts/fractions/compounds. All the combinations showed toxicity and synergistic activity. Leaf/bark extracts and seed oil (0.25-2 mg L-1) significantly inhibits the AChE and GST activity in A. craccivora. Based on field bio-efficacy studies, the leaf extract/seed oil or their combinations can be recommended for development of botanical formulation for the control of aphid.

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.

Morpho-agronomy performance, seed nutrition content, and Aphis craccivora resistance of cowpea (Vigna unguiculata) genotypes

Sas MGA, Wahyu Y, Syukur M, Hidayat P. 2021. Morpho-agronomy performance, seed nutrition content, and Aphis craccivora resistance of cowpea (Vigna unguiculata) genotypes. Biodiversitas 22: 4320-4326. Cowpea (Vigna unguiculata subsp. unguiculata) is an agricultural commodity that can be a source of vegetable protein and replace the need for soy as a food ingredient. The wide adaptability under sub-optimum conditions placed cowpeas as the choice to be developed. This study aimed to evaluate the cowpea genotype’s agronomic performance and resistance to Aphis craccivora to be proposed as superior genotypes. Observations were made on the morpho-agronomic characters, including the color of the young pods and dry seeds, the number of pods, the productivity of fresh pods and dried seeds, and the nutrition content. The resistance to Aphis craccivora was evaluated using a no-choice test whole plant for the resistance and tolerance evaluation. This study showed that the productivity of young pods (4.86-15.13 tons ha-1), dry seed productivity (0.83-2.71 tons ha-1). The protein content differed significantly among the 20 genotypes ranging from 19.24% to 24.45%. Aphid infestation significantly inhibited plant growth compared with non-infested plants. Infestation of Aphis craccivora decreased the dry weight of the plant by about 20% to 70%. Based on the aphid population, the 20 genotypes were classified into medium-high to very high aphid damage intensity.