Organisms are always confronted with multiple stressors simultaneously. Combinations of stressors, rather than single stressor, may be more appropriate in evaluating the stress they experience. N. barkeri is one of predatory mite species that are commercialized for controlling spider mites. However, their biological control efficiency was often reduced because of high temperature and desiccation in summer. To understand how to improve the tolerance of N. barkeri to combined heat and desiccation stress, we pre-exposed the adult female of N. barkeri to high temperature, desiccation and high temperature × desiccation stress for acclimation. After proper recovery time, mites were subjected to high temperature × desiccation stress again to detect the acclimation effects. The results are as follows: (1) No decrease in mortality rate were observed under high temperature × desiccation stress after heat acclimation. Instead, it increased significantly with acclimation temperature and time. (2) Dehydration acclimation both at 25 °C and high temperatures reduced mortality rate under high temperature × desiccation stress. Mortality rate was only significantly correlated with the amount of water loss, but not with temperature or water loss rate in acclimation, suggesting the increased tolerance is related to dehydration stress rather than heat stress. Among all acclimations, chronic dehydration at 25 °C, 50% relative humidity were the most effective treatment. This study indicated dehydration acclimation is effective to enhance tolerance of N. barkeri to combined heat and desiccation stress, which can improve the efficiency of biological control under multiple stressors.

Pre-stimulation of plants can change their resistance mechanisms, thereby enhancing their defense responses. Beauveria bassiana, a broad-spectrum entomogenous fungi, can also induce plant defenses, but it received little attention. Here, we show that B. bassiana can act as a stimulus to prime tomato defense responses, improving resistance in the plant to herbivore stress. The results illustrated that four defense genes (PIN2, PR2, PAL, and MPK3) were upregulated in all B. bassiana treatments, especially the phenylalanine deaminase (PAL) gene, which was highly expressed in tomato plants after B. bassiana inoculation. Feeding through Bemisia tabaci resulted in a weak upregulation of defense genes. However, in combined fungal inoculation and B. tabaci feeding, a total of nine defense genes were upregulated, among which five genes—PAL, PPO, PIN2, PR2, and PR1—were closely related to the phenol synthesis. The results of tomato plant metabolism showed that B. bassiana mainly activates tomato phenylpropane metabolic pathways, with this modulation being influenced by jasmonate. Further explorations revealed a significant enhancement in the antioxidant capacity of the plants, as evidenced by the determination of their antioxidant compounds and the coloration of leaf phenolic substances. Thus, entomopathogenic fungi can act as an exogenous substance to activate the defense responses of tomatoes without damaging the plant, indicating a good potential for developing applications using B. bassiana to promote resistance in tomatoes for pest management.

Blue oat mite species, including Penthaleus major and P. tectus, are pests widely distributed across China that cause damage to winter wheat. This study evaluated the genetic diversity of P. major and P. tectus on Triticum hosts collected from 23 geographic locations based on mitochondrial cytochrome c oxidase subunit I (COI) sequences. We identified nine haplotypes in 438 P. major individuals from 21 geographic locations and five haplotypes in 139 P. tectus individuals from 11 geographic locations. Meanwhile, P. major exhibits high values of haplotype diversity (Hd) and nucleotide diversity (Pi) (Hd = 0.534 > 0.5 and Pi = 0.012 > 0.005), representing a large stable population with a long evolutionary history. P. tectus shows low values of Hd and Pi (Hd = 0.112 < 0.5 and Pi = 0 < 0.005), which suggest recent founder events. Moreover, demographic analysis suggested that P. major and P. tectus have not undergone a recent population expansion. The lowest genetic variation was observed in Xiangzhou (XZ-HB), Zaoyang (ZY-HB), Siyang (SY-JS), and Rongxian (RX-SC), with only one species and one haplotype identified in over 30 individuals. Robust genetic differentiation was found in P. major compared to P. tectus, which provides a theoretical basis for the widespread distribution of P. major in China.

Trade-off theory has long been the central to evolutionary biology and is extensively employed to explain the correlations between life-history traits. It is generally accepted that trade-off occurs when one trait cannot increase without a decrease in another. In this study, we collected data on spider mites (70 papers for females and 35 papers for males) and explored the relationships between life-history traits to test the trade-off theory in both sexes. The results demonstrate that for both males and females, there was a statistically significant negative correlation between developmental rate and lifespan, in agreement with the trade-off theory. However, in contradiction with our assumption, the developmental rate of females was positively correlated with maximum daily fecundity, but not with the total fecundity. This indicates that developing fast does not necessarily bring the cost to late life-history traits. The long-lived females also showed higher lifetime fecundity, contrary to our prediction that investment in survival comes at the cost of lower investment in reproduction. These fundings are congruent with life history theory in that spider mites “live fast, die young”, convincing the trade-off between growth and longevity. Nevertheless, this study highlights that there is no clear evidence that spider mites trade off growth and survival for reproduction. The implications of this phenomenon are discussed.

The stink bug, Eocanthecona furcellata Wolff (Hemiptera: Pentatomidae) shows significant promise as a biological control agent against lepidopteran pests in tropical and subtropical areas. However, securing suitable food remains a persistent issue for the mass rearing of this beneficial insect. To understand how different feeding strategies impact reproductive success, we evaluated their effects on critical life table parameters and ovary development using a range of feeding options: natural prey Spodoptera litura Fabricius (Lepidoptera: Noctuidae) and Spodoptera exigua Hubner, alternative prey Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae), and an advanced artificial diet. E. furcellata fed on S. litura had the highest fecundity (326.96 eggs) and net reproduction rate (86.04 offspring). Moreover, those fed T. molitor exhibited the highest survival rate during the nymph stage (61.86%). Among all tested treatments, ovarian tube length reached its peak on the 14th day following the emergence of the adult. The group fed S. litura had the longest average length (4.021 mm), followed by those fed S. exigua (3.986 mm) and T. molitor (3.904 mm). Notably, E. furcellata fed on S. exigua displayed the highest number of fully developed follicles between days 3 and 21 after emergence. This research underscores the efficacy of utilizing natural prey, especially S. litura, and alternative prey, T. molitor, for enhancing the reproductive success and survival of E. furcellata, providing critical insights for optimizing mass-rearing techniques and informing integrated pest management strategies that leverage this beneficial insect for effective biological control across diverse agricultural systems.