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.

Varieties’ Response of Vegetable Cowpea to Mechanical Inoculation of Cowpea Aphid-Borne Mosaic Virus in Burkina Faso

Vegetable cowpea is eaten mainly fresh, in the form of young, immature pods, tender and sweet like the common bean. However, like cowpea with seeds, vegetable cowpea experience yield losses due to the cowpea aphid-borne mosaic virus (CABMV). This study aims to improve yields through the development of vegetable cowpea varieties resistant to CABMV. The study focused on ten varieties of vegetable cowpea, carried out in a greenhouse at the Kamboinsé research station using a randomized complete block design with three replications, all inoculated with CABMV. The data collection concerned resistance parameters. Mechanical inoculation made it possible to observe various symptoms of CABMV, thus highlighting the existence of variability within the varieties tested. Strong correlations were observed between several variables. Thus, the varieties of vegetable cowpea IT85F-2089-5, UG-CP-8, IT85F-2805-5 and Telma were identified as resistant, because belonging to the low severity classes and having a low value of area under the disease progress curve. On the other hand, the varieties RW-CP-5, UG-CP-6, IT83S-911, niébé baguette grimpant possessing a high severity class were judged to be susceptible. These resistant varieties will thus be able to contribute to the improvement of production and the protection of cowpea resources in Burkina.

​​Screening Cowpea Genotypes for Resistance to Cowpea Aphid Borne Mosaic Virus (CABMV) and Cowpea Severe Mosaic Virus (CPSMV) in Paraguay

Background: Cowpea [Vigna unguiculata (L) Walp.] is one of the Paraguayan rural families’ main crops, serving as an essential protein and carbohydrate source. Cowpea aphid borne mosaic virus (CABMV) and cowpea severe mosaic virus (CPSMV) were identified infecting cowpea plants. Disease control caused by both viruses is difficult because there is no information about local cowpea resistant cultivars and vector control is not practical. Methods: In the present work, sixteen cowpea genotypes/cultivars were mechanically inoculated with local isolates of CABMV and CPSMV to identify resistant genotypes/cultivars that can be used in breeding programs. Virus infections were determined by symptoms expression and confirmed by PTA-ELISA. Result: Genotypes Arroz rojo (V. angularis), TVu 379, TVu 382, TE94-256-2E and TE97-309G-9 were resistant to CABMV. Genotypes Arroz rojo (V. angularis), CNCX-698-128F, TVu 379, TVu 382, TVu-3961, TE97-309G-9 and TE97-309G-3 were resistant to CPSMV. Overall, this study showed that local cowpea cultivars do not offer any resistance to virus infection and the need for resistant germplasms for cowpea breeding programs in the country.

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.

Flupyradifurone Induces Transgenerational Hormesis Effects in the Cowpea Aphid, Aphis Craccivora (Koch)

Insecticide induced-hormesis, a biphasic phenomenon ,with low-dose stimulation and high-dose inhibition, which effectively contributes to pest resurgence. Although cowpea aphid, Aphis craccivora (Koch) (Homoptera: Aphididae), is the most infection insect to legume crops in Egypt, its’ hormesis to flupyradifurone did not previously establish. Therefore, age-stage two-sex life analysis was used to investigate the sublethal and transgenerational effects of flupyradifurone on two successive generations of A. craccivora. Leaf-dip bioassay method revealed high toxicity of flupyradifurone against A. craccivora with LC50 value of 1.82 mg L-1 after 48 h exposure. Treatment of parent generation (F0) with LC10 and LC25 of flupyradifurone significantly increased the longevity and fecundity of the directly exposed adults. The results of transgenerational effects showed that treatment of (F0) with LC25 induced a significant hormetic effects in progeny generation (F1). Furthermore, flupyradifurone at LC25 significantly enhanced the biological traits such as intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R0) compared with the control. Similarly, both LC10 and LC25 caused a significant increase in the mean generation time T (d). Conversely ,both treatments had a significant decrease in the doubling time (DT). In conclusion, the obtained data demonstrate that exposure of (F0) to flupyradifurone at LC10 and LC25 enhanced longevity and fecundity in of the directly exposed adults of A. craccivora and induced transgenerational hormesis across the subsequent (F1) generation. These grades must be taken into consideration when using flupyradifurone against cowpea aphids.