Abstract
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.
Highlights
Plants produce secondary metabolites and chemical substances to protect themselves from the attack of pests and pathogens [1]
The three plants P. penninervia, P. crispa and E. arabicus belong to the Asteraceae family, they contained different flavonoids and different concentrations of total flavonoids
The comparison between the LC50 values of each plant extract for aphids and the green-lacewing larvae by relative median potency analyses indicated that P. penninervia (RMP = 0.516, 95% CI: 0.382, 0.665), O. baccatus (RMP = 0.404, 95% CI: 0.287, 0.529)
Summary
Plants produce secondary metabolites and chemical substances to protect themselves from the attack of pests and pathogens [1]. There is a growing need for new active substances and products for pest control that decrease the unfavorable impacts of chemical insecticides on the environment and especially on human health [2]. Insects 2020, 11, 398 and a decrease in the egg viability of insects These botanical extracts are generally less harmful to the environment, low cost, and their use as food ingredients indicate their low toxicity to humans [3,4]. Botanical aphicidal agents biodegrade naturally and are less persistent than synthetic chemical insecticides. Many studies have attempted to improve plant-derived aphicidal agents, and various biologically active compounds that are toxic to insect pests have been isolated and identified [5]. Numerous species of Pulicaria genus are rich in several botanical compounds such as flavonoids, isocomene, acetylenes, monoterpenes and sesquiterpene lactones. The Euryops genus belongs to the Asteraceae family and includes 97 species
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