Several flowering plant species enhance parasitoid performance without benefiting host pests: Implications for conservation biological control in maize agroecosystems

• The potential biological control of six candidate nectary plants was evaluated. • Shah chong tee and basils boosted the longevity of tested parasitoids remarkably than others. • These two nectary plants also significantly enhanced tested parasitoids fecundity. • Shah chong tee and basils had no benefit for four main lepidopteran pests of maize. • Shah chong tee and basils are promising nectary plants for maize pest biological control. Suitable nectary plants could supply natural enemies for essential nutrients that improve survival, reproduction, and pest-control efficiency. This study evaluated six candidate nectary plants ( Brassica napus , Cosmos sulphureus , Cnidium monnieri , Gypsophila paniculata , Kalanchoe blossfeldiana , and Ocimum basilicum ) for their potential biological control of six key parasitic natural enemies ( Trichogramma chilonis , Trichogramma dendrolimi , Trichogramma japonicum , Trichogramma ostriniae , Microplitis mediator , and Macrocentrus cingulum ) and their impacts on four lepidopteran pest species ( Ostrinia furnacalis , Spodoptera exigua , Spodoptera frugiperda , and Helicoverpa armigera ) in maize. Results showed that B. napus flowers significantly extended the lifespan of T. chilonis , M. cingulum females, and both male and female of T. japonicum , while also enhancing the fecundity of T. dendrolimi and T. japonicum . Cosmos sulphureus prolonged the longevity of T. ostriniae males and both sexes of T. japonicum . Cnidium monnieri significantly increased the longevity of all tested parasitoids, including female T. ostriniae , and boosted the fecundity of T. chilonis , T. dendrolimi, and T. japonicum . Ocimum basilicum enhanced the longevity of all tested parasitoids, regardless of sex, and promoted fecundity in T. chilonis , T. dendrolimi, and T. japonicum . Importantly, C. monnieri had no impact on pest longevity. Ocimum basilicum only increased longevity in male S. exigua , with no other significant effects on pest reproduction or survival. These findings indicate that C. monnieri and O. basilicum are promising nectary plants for integration into maize cropping systems to enhance biological control of insect pest.