The adaptive ability of Hyphantria cunea larvae to induced chemical defenses of Morus alba, a high-preference host plant

Hyphantria cunea is a significant invasive pest characterized by its polyphagous nature and robust reproductive capabilities. In the present study, the interaction between Morus alba seedlings and H. cunea larvae was revealed by combining the induced chemical defense of M. alba with the adaptive strategies of H. cunea larvae. Larval feeding damage swiftly triggers both local and systemic chemical defenses in M. alba , involving nutrients (amino acids, proteins, soluble sugars), secondary metabolites (total phenol, total flavone, tannin, lignin), and flavonoid synthesis pathways. Mild damage induced defense responses in M. alba that persisted until day 21, inhibiting the growth of a subsequent batch of H. cunea larvae after 7 days of continuous feeding. Conversely, at moderate damage levels, these induced defenses diminished by day 21, temporarily failing to affect the larval growth. In response to these defenses, H. cunea larvae significantly up-regulated the expression of most detoxification enzyme genes, which remained active throughout. Initially, some trypsin and lipase genes in the larvae were significantly up-regulated, but with prolonged feeding, gene expression shifted towards the α-amylase family. Feeding by H. cunea larvae can stimulate the induced chemical defense of M. alba . The H. cunea larvae can adapt to the M. alba chemical defense by modulating their digestive and metabolic detoxification mechanisms. Graphical abstract