Endosymbionts play an essential role in the biology, physiology and immunity of insects. Many insects, including the whitefly Bemisia tabaci, are infected with the facultative endosymbiont Rickettsia. However, the mutualism between Rickettsia and its whitefly host remains unclear. This study investigated the biological and physiological benefits of Rickettsia infection to B. tabaci. Results revealed that infection of Rickettsia increased the fertility, the survival rate from nymph to adult and the number of female whiteflies. In addition, this facilitation caused a significant reduction in nymphal developmental duration but did not affect percentage rate of egg hatching. Rickettsia infected B. tabaci had significantly higher glycogen, soluble sugar and trehalose contents than Rickettsia negative B. tabaci individuals. Rickettsia also improved the immunity of its whitefly hosts. Rickettsia infested B. tabaci had lower mortality rates and higher semi-lethal concentrations (LC₅₀) when exposed to the fungus Akanthomyces attenuatus and the insecticides imidacloprid and spirotetramat. The percentage of parasitism by Encarsia formosa was also reduced by Rickettsia infection. Overall, Rickettsia infection benefits B. tabaci by improving the nutritional composition of its host, and also protects B. tabaci by enhancing its resistance towards insecticides (imidacloprid and spirotetramat), entomopathogenic fungi (A. attenuatus) and its main parasitoid (E. formosa); all of which could significantly impact on current management strategies.

An increasing body of research has underscored the significant impact of non-consumptive effects on the dynamics of prey pests, encompassing growth, development, reproduction, and metabolism across various vertebrate and invertebrate taxa, rivaling the influence of consumption effects. In our investigation, we delved into the non-consumptive effects exerted by the natural predatory enemy Harmonia axyridis on the reproductive capacity and metabolism of Spodoptera frugiperda adults. Our findings revealed a substantial decrease in the reproductive ability of S. frugiperda adults when exposed to the non-consumptive effects of H. axyridis. Concurrently, we observed an elevation in hydrogen peroxide (H₂O₂) content and the activities of antioxidant enzymes such as superoxide dismutases (SODs), catalases (CATs), and peroxidases (PODs). Furthermore, notable alterations were detected in energy metabolism, characterized by heightened triglyceride levels and diminished glycogen and trehalose concentrations. These outcomes underscored the adaptive response of the pest aimed at mitigating non-consumptive adverse effects by augmenting antioxidant enzyme activity to counteract oxidative stress and minimize cellular damage. Nonetheless, this defensive mechanism entails a significant expenditure of energy resources, resulting in shifts in energy utilization. Elevated triglyceride levels and reduced glycogen and trehalose concentrations diminish available resources for reproductive processes, such as egg laying, ultimately culminating in decreased fecundity. This study contributes novel insights into the non-consumptive effects observed in insects, while also furnishing valuable insights into the mechanisms underlying insect stress responses.

The effects of predatory natural enemies on their prey or hosts involve both consumption and non-consumptive effects. This study investigated the non-consumptive effects of the predator, Harmonia axyridis (Coleoptera: Coccinellidae) on 1st, 2nd and 3rd instar larvae of Spodoptera frugiperda. We exposed larvae of different instars to the predator and assessed various parameters using a combination of biological and biochemical methods. Exposure to the predator significantly affected the growth and development of the S. frugiperda caterpillars. Firstly, the developmental duration of S. frugiperda larvae in the 1st–3rd instars and the pupal stage were notably prolonged. Moreover, we observed significant effects on pupal mass, pupal abnormality rate and emergence rate. These non-consumptive effects were gradually weakened with an increase in the larval stage exposed to the predator. Antioxidant enzyme activities including catalase (CAT) peroxidase (POD) and superoxide dismutase (SOD) activity increased significantly. Additionally, organismal triglyceride, trehalose and glycogen content were significantly altered by non-consumptive effects, while protein content showed no significant change. Spodoptera frugiperda larvae increased the activity of antioxidant enzymes in response to potential predators to mitigate oxidative stress and reduce cellular and tissue damage. This resources redistribution towards survival may inhibit growth and development of the species and further exacerbate these non-consumptive effects. These findings highlight the importance of considering non-consumptive effects in pest-management strategies to optimize control measures in agricultural systems.