Abstract
ABSTRACT Entomopathogenic microorganisms are increasingly used to control Brevicoryne brassicae L. (Hemiptera: Aphididae). Traditionally isolated from soil or plants, the focus on terrestrial environments limits the bioprospecting of promising isolates from marine environments. This study evaluated the lethal and sublethal effects of five marine-derived actinobacteria of the genus Streptomyces on B. brassicae. Cabbage leaves or seedlings were immersed in various concentrations of actinobacteria and provided as food to B. brassicae. Exposure of nymphs up to 48 h old to 3 × 109 cells mL−1 of different strains revealed that S. variabilis was the most promising, causing 100% mortality after 96 h, with an estimated LC50 of 2.0 × 106 cells mL−1 (95% CI: 1.2 × 106–3.4 × 106). Exposure of B. brassicae to the LC25 of S. variabilis (1.2 × 105 cells mL−1) did not affect the net reproduction rate (Ro), average generation time (T), intrinsic rate of population growth (rm), finite capacity for increase (λ), or doubling time (DT). However, concentrations of 1.5 × 105 and 1.5 × 109 cells mL−1 exhibited a deterrent effect on B. brassicae, significantly reducing feeding. The deleterious effects of S. variabilis on B. brassicae suggest the feasibility of using marine isolates in developing new bioinsecticides, contributing to more sustainable agriculture and reducing dependence on synthetic insecticides.
Published Version
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