Ecological wisdom: functional plant Cosmos bipinnata enhances fitness traits of predator Harmonia axyridis strengthening biological control in greenhouse production

Functional plants play a pivotal role in plant protection by bolstering the populations of pests’ natural enemies. When utilized as companion plants, they serve as crucial components in conservation biological control. A systematic analysis of the ecological functions of candidate companion plant species is of utmost importance for effectively attracting and sustaining natural enemies, thereby promoting biological control strategies. In this study, we comprehensively examined the impact of Cosmos bipinnata (Asteraceae) on the olfactory behavior, lifespan and survival of Harmonia axyridis , and evaluated its function in maintaining field populations and pest control capabilities. Compared to the absence of companion plants, C. bipinnata leaves at the vegetative stage significantly attracted H. axyridis females in the Y-tube olfactometer, while both females and males significantly avoided C. bipinnata during the flowering stage. Additionally, females lived significantly longer when offered 5 C. bipinnata flowers daily compared to those with no food source. Moreover, providing C. bipinnata flowers in addition to aphids (in deprivation or ad libitum ) also significantly increased egg production of H. axyridis . Furthermore, in greenhouse pepper production, the introduction of C. bipinnata increased the colonization rate of H. axyridis released in the early stages, thus achieving effective pest control in the short term. In the long term, incorporating C. bipinnata helped sustain multiple developmental stages of H. axyridis populations, accelerating pest suppression and enhancing pepper yield throughout the entire production cycle. • Utilizing functional plants to enhance the efficacy of predators is a successful case of applying ecological wisdom to biological control. • Volatiles emitted by Cosmos bipinnata exerted an attractive effect on Harmonia axyridis females during the vegetative stage. • The inflorescences of C. bipinnata increased the survival rate and reproduction ability of H. axyridis females. • As a companion plant in the pepper greenhouse, C. bipinnata promoted aphid suppression through the augmentation of the ladybird population.