Botanical insecticides that degrade rapidly are safer than persistent synthetic chemical insecticides, less harmful to the environment, decrease production costs and are not likely to cause insecticide resistance among pests. This study aimed to evaluate the effect of five different botanical extracts on the bean aphid, Aphis craccivora and the 2nd larval instar of the green lacewing, Chrysoperla carnea under laboratory conditions. Also, the flavonoids in the methanolic extracts of these tested plants were detected using HPLC analysis. The data from the HPLC analysis indicated that the tested plants differed in their flavonoid components. The total flavonoids were 869.4, 1125.6, 721.4, 1667.8 and 2025.9 mg/kg in Psiadia penninervia, Salvia officinalis, Ochradenus baccatus, Pulicaria crispa and Euryops arabicus, respectively. Moreover, there were many variations among these plants in the amount of each compound. The lethal concentration (LC50) value of P. penninervia extract on aphids was the lowest among all of the plants (128.546 µg/mL) followed by O. baccatus (626.461 µg/mL). Also, the LC50 value of P. penninervia extract on the 2nd larval instar of C. carnea (232.095 µg/mL) was significantly lower than those of all other four plant species extracts, while the other four plants did not show significant differences among them according to relative median potency analyses. Accordingly, O. baccatus extract had a strong effect on aphids and was safest for the predator. This finding suggests that O. baccatus could be exploited and further developed as an effective plant extract-based insecticide to be utilized in integrated pest management (IPM) programs against A. craccivora.

Background As different biogeographic strains and isolates of entomopathogenic fungi vary in their genetic, enzymatic and pathogenic characteristics, this study assessed the virulence of 2 indigenous strains of Beauveria bassiana (Balsam) Vuillemin and Metarhizium anisopliae (Metschn.) Sorokin (Ascomycota, Hypocreales: Clavicipitaceae), isolated from naturally infected insect cadavers, against the 3rd instar nymphs of Myzus persicae (Sulzer) (Hemiptera: Aphididae) and 3rd instar larvae of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) using leaf-dip and larval-dip methods, respectively. Results Both fungal isolates exhibited considerable pathogenicity against M. persicae and S. frugiperda. Mortality in all bioassays was conidial concentration and exposure time dependent and increased significantly along with both factors (R2 = 0.86–0.99 for B. bassiana and 0.82–0.94 for M. anisopliae). Moreover, M. anisopliae isolate appeared more virulent to S. frugiperda larvae than B. bassiana isolate, while the later fungal isolate was more lethal to M. persicae nymphs than the former one. At the highest conidial concentration (1.0 × 109 conidia/ml), M. anisopliae caused maximum mean mortality of S. frugiperda (88%) and M. persicae (65%) and B. bassiana exhibited maximum mean mortality of S. frugiperda (76%) and M. persicae (94%). Moreover, probit regression analyses showed LT50 values for M. persicae of 4.57 and 6.86 days at 1.0 × 109 conidia/ml for the isolates of B. bassiana and M. anisopliae, respectively, while LC50 values were 7.75 × 106 and 8.70 × 107 conidia/ml after 10th day of application, for the isolates of B. bassiana and M. anisopliae, respectively, against M. persicae. Similarly, LT50 values for S. frugiperda were 7.75 and 7.03 days for 1.0 × 109 conidia/ml concentration and LC50 values were 2.84 × 107 and 8.84 × 105 conidia/ml at 10th day data for the isolates of B. bassiana and M. anisopliae, respectively. Conclusion Overall study results demonstrated the effectiveness of B. bassiana and M. anisopliae against M. persicae and S. frugiperda, respectively. However, field evaluations of these indigenously isolated promising fungal strains against these insect pests.

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