Saline-alkali stress triggers negative bottom-up effects on Binodoxys communis Gahan, a parasitoid of cotton aphid

In agro-ecosystems, parasitoids can be influenced by bottom-up forces, particularly abiotic stresses on their host’s plants, which can modulate parasitoid host preference and performance. Saline-alkali stress has emerged as a significant concern in recent years, yet research examining parasitoid performance under such conditions remains limited. This study investigated the effects of saline stress, alkali stress and mixed stress, simulated using NaCl and Na 2 CO 3 on Binodoxys communis Gahan, a primary parasitoid of the cotton aphid, Aphis gossypii Glover. Our results revealed significant adverse effects of saline-alkali stresses on B. communis , which manifested as reduced rates of parasitism, longer larval developmental periods, reduced adult lifespans, and reduced adult survival rates. Furthermore, B. communis exhibited significantly reduced cumulative fecundity, a lower female sex ratio (F /F + M), and reduced values for population growth parameters (intrinsic rate r m , finite rate of increase λ , and net reproductive rate R 0 ). Regression analysis, based on data from our previous research, found a significant positive relationship between the R 0 values of B. communis and A. gossypii , while weakly positive correlations were observed between these stresses and cotton aphid population growth ( r m ) and the population finite rate in increase ( λ ). These findings suggest that saline-alkali stress reduces B. communis fitness through bottom-up effects, and they provide a theoretical foundation for integrated pest management and biological control strategies for farmers in extreme environments.