Evaluation of lethal and sublethal effects of laminarin on the green peach aphid, Myzus persicae, under extended laboratory conditions

Recent studies have opened the way for using elicitor-induced resistance in plants as a method to control arthropod pests. In this study, 1,3-beta-glucan laminarin, an elicitor of disease resistance in plants, was tested on the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), on peach [Prunus persica (L.) Batsch, Rosaceae] plantlets and evaluated its effects on short-term mortality and population growth. Laminarin exposure did not affect aphid survival in the short term; however, laminarin-treated peach plants sustained fewer nymphs and adults in comparison with the control. Aphid populations on plants treated with laminarin declined significantly over the sampling period compared to the control. Moreover, the demographic parameters net reproductive rate (R-0), finite rate of increase (lambda), and intrinsic rate of increase (r(m)), all showed decreasing trends in aphid populations reared on laminarin-treated plants. The decline in aphid populations exposed to laminarin seemed to mainly be linked to reduced adult survival, slower nymph development, and lower nymph survival and only marginally to changes in reproduction outcome. Changes in gene expression causing the final production of defence chemicals by peach plants may contribute to explaining the results. However, potential direct effects of laminarin on M. persicae feeding activity and probing behaviour cannot be ruled out. This study provides evidence that, although laminarin did not display insecticidal activity in the short term, this elicitor caused sublethal effects, significantly reducing aphid populations.