High Nitrogen Enhances Maize Susceptibility to Holotrichia parallela via β-Caryophyllene-Mediated Olfactory Recognition and Jasmonate Suppression

Excessive nitrogen application not only affects plant development but also significantly influences plant–pest interactions. This study investigates how nitrogen fertilization modifies the metabolism of maize (Zea mays) and its interaction with Holotrichia parallela, a key soil-dwelling pest. High-nitrogen (HN) conditions increased the emission of volatile organic compounds (VOCs), with β-caryophyllene and palmitic acid strongly attracting larvae behavior selection, and β-caryophyllene attracting female oviposition. RNA interference targeting HparOR19 and HparOR22 genes confirmed the role of β-caryophyllene in pest olfactory recognition. Conversely, low-nitrogen (LN) conditions stimulated jasmonic acid (JA)-related defenses, while HN promoted the production of primary metabolites such as glucose, fructose, and sucrose, which act as feeding stimulants. These findings highlight the intricate relationship among nitrogen fertilization, maize metabolism, and pest behavior, underscoring the necessity of integrating metabolic insights into effective pest management strategies.