LAUSR

Induced defence allows plants to manage energy reserves more efficiently by synthesizing defence compounds only when needed. A risk of induced defence is that when plants are challenged by herbivores, they may suffer considerable damage before the defence is mounted. Priming can cause a state of readiness for the induction of the defence response, leading to a reduction in the damage received in an energy‐efficient and less costly manner. Our objective was to verify whether seed coating with jasmonic acid (JA) and chitosan (CH) could prime plants against chewing and sap‐feeding herbivores by affecting their herbivory of treated plants. We used Brassica oleracea L. var. capitata cv. Derby Day (Brassicaceae) seeds treated with JA and CH, second‐instar Plutella xylostella L. (Lepidoptera: Plutellidae), and newborn nymphs of Myzus persicae (Sulzer) (Hemiptera: Aphididae). We evaluated life‐history, performance, and fecundity traits of the insects. Neither JA nor CH affected B. oleracea leaf area. Both JA and CH affected P. xylostella. JA reduced the mean relative growth rate of P. xylostella and led to 84% pre‐imaginal mortality, whereas CH reduced oviposition. JA reduced significantly the intrinsic rate of increase in M. persicae, whereas CH did not differ from the control. Therefore, JA and CH seed coating lead to long‐term defence priming in B. oleracea against chewing and sap‐feeding insects.