Penthaleus major (Dugés) is a significant agricultural pest that attacks various pasture, vegetable, and crop plants. Temperature plays a critical role in the life history of P. major. However, there is limited understanding of its life table at different temperatures and cold tolerance. This study aimed to elucidate the performance of P. major by constructing life tables at 6, 9, 12, 15, 18, 21, and 24 °C. The results showed that P. major successfully developed at 9‒21 °C. However, no adults emerged at 6°C, and no eggs hatched at 24 °C. The highest intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and gross reproductive rate (GRR) were observed at 12 °C. The supercooling point (SCP) exhibited significant variations at different developmental stages. The highest SCP (‒9.75 °C) was recorded in 10-day-old female adults, while the lowest SCP (‒24.37 °C) was observed in larvae. For female adult mites of 2, 6, and 10 days old, the low lethal temperatures (LLT50) were ‒14.63, ‒12.03, and ‒11.08 °C, respectively. This study provided valuable insights for modeling and predicting the population dynamics of P. major in the field and offered implications for developing successful management strategies.

BACKGROUND:Entomopathogenic fungi (EPF) treatment of plants may affect the survival and feeding preferences of herbivorous pests. However, comprehensive studies on the fitness across their entire life cycle, feeding behavior, and physiological changes in herbivores consuming EPF-treated plants within the tripartite interactions of EPF, plants, and pests are still limited. In this study, we utilized life tables, electrical penetration graph (EPG), and metabolomics to uncover the biological and physiological characteristics of Bemisia tabaci on tomato plants inoculated with Beauveria bassiana through root irrigation. RESULTS:Our study indicated that Beauveria bassiana Bb252 can penetrate the entire tissue from the point of inoculation, primarily colonizing the intercellular spaces and vascular tissue. However, this colonization is temporary, lasting no more than 35 days. Moreover, the population fitness and feeding behavior of Bemisia tabaci on tomato plants treated with Beauveria bassiana via root irrigation were significantly affected, showing a substantial 41.4% decrease in net reproductive rate (R0), a notable reduction in watery salivation, and shortened phloem ingestion. Lastly, we observed a significant decrease in hormones and amino acids of whiteflies that fed on Beauveria bassiana-treated tomato plants by root irrigation. CONCLUSIONS:Our results indicated that the endophyte, Beauveria bassiana Bb252, reduced demographic fitness of Bemisia tabaci by altering its hormones and amino acids levels. These findings enhance our understanding of multitrophic interactions in integrated pest management. © 2024 Society of Chemical Industry.

Beauveria bassiana acts as an endophytic fungus that controls herbivorous pests by stimulating plant defenses and inducing systemic resistance. Through multiomics analysis, 325 differential metabolites and 1739 differential expressed genes were observed in tomatoes treated with B. bassiana by root irrigation; meanwhile, 152 differential metabolites and 1002 differential genes were observed in tomatoes treated by local leaf spraying. Among the upregulated metabolites were α-solanine, 5-O-caffeoylshikimic acid, clerodendrin A, and peucedanin, which demonstrated anti-insect activity. These differential metabolites were primarily associated with alkaloid biosynthesis, flavonoid biosynthesis, and tryptophan metabolism pathways. Furthermore, the gene silencing of UDP-glucose:sterol glucosyltransferase, a gene involved in α-solanine synthesis, indicated that B. bassiana could inhibit the reproduction of whiteflies by regulating α-solanine. This study highlighted the ability of B. bassiana to modulate plant secondary metabolites and emphasized the significance of understanding and harnessing multitrophic interactions of endophytic B. bassiana for sustainable agriculture.

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.

Abstract The whitefly Bemisia tabaci is a cosmopolitan, polyphagous agricultural pest that poses serious threats to agricultural production globally. Beauveria bassiana, an entomopathogenic fungi (EPF), cannot only directly kill a variety of pests but also inhibit the occurrence of pests as fungal endophytes within plants. In this study, we explored how the introduction of B. bassiana as endophytes into tomatoes (Solanum lycopersicum) affected the fitness and feeding behaviour of whiteflies. The results showed a significant difference in the fertility of B. tabaci on tomatoes treated with B. bassiana by root irrigation, B. bassiana by local leaf spraying, and 0.05% Tween 80 solution, among which the number of eggs laid was the lowest on tomatoes treated with B. bassiana by root irrigation. Furthermore, B. tabaci fed on tomatoes treated with EPF by root irrigation showed a significantly higher mortality rate in each stage than control plants treated with 0.05% Tween 80 by constructing an age-stage, two-sex life table. In addition, the intrinsic rate of increase (r), the finite rate of increase (λ) and the net reproductive rate (R0) of the B. tabaci population on tomatoes treated with EPF by root irrigation were all significantly lower than those of the control. Moreover, tomatoes treated by root irrigation had a significant negative effect on the feeding behaviour of B. tabaci by shortening the duration of watery salivation and phloem ingestion. Our results indicated that B. bassiana effectively inhibited the occurrence of whitefly as endophytes. These findings enhanced our understanding of the inhibition of endophytic EPF on pests.

Biological control of spider mites in hot and dry weather is a serious technical issue. A high-temperature adapted strain (HTAS) of the predatory mite Neoseiulus barkeri Hughes was selected from its conventional strain (CS), via long-term heat acclimation and frequent heat hardenings in our previous studies. However, the environment of high temperature is usually associated with enhanced ultraviolet (UV) radiation. In the present study, the physiological effects of UV-B radiation on survival rate and egg damage of N. barkeri were investigated, as well as the activities and expression profiles of antioxidant enzymes to UV-B radiation stress. UV-B radiation had deleterious effects on egg hatchability and survival of N. barkeri. Adults of the HTAS strain were less UV-B resistant than those of the CS strain; they also had lower levels of enzymatic activity of superoxide dismutase (SOD) and catalase against oxidative damage and weaker upregulation of SOD genes. The mRNA expression of three SOD genes of CS adult females immediately increased whereas that of HTAS showed almost no difference under UV-B stress for 1h. The results showed the HTAS of N. barkeri had lower fitness under UV-B stress compared with the CS of N. barkeri. These results suggested that long-term heat acclimation may exert a profound impact on the developmental physiology of N. barkeri.

To explore the effects of heat shock proteins in the conventional strain (CS) and high temperature-adapted strain (HTAS) of Neoseiulus barkeri, we cloned and characterized the cDNA of the NbHsp40, NbHsp60, NbHsp70, and NbHsp90 genes and examined changes in expression levels with short-term exposure to heat or cold stress. All four of the genes showed highly conserved amino acid sequences and high homology to Galendromus occidentalis and N. cucumeris. Phylogenetic analysis of NbHsps indicated a high consistency with the known genes of model insects. These results demonstrate variations in the sensitivity of NbHsps to heat or cold stress; i.e., the expression of NbHsp60 did not change with the application of heat and cold stress, NbHsp90 and NbHsp40 were upregulated at high temperature compared to that at low temperature responses, and the expression of NbHsp70 increased with both heat and cold stress. Hsp expression also differed between the two strains: The application of a 40°C heat shock resulted in a decrease in the expression of NbHsp40/70/90 in the CS within 1–2 h, but increased in the HTAS strain in 2 h. However, exposure to cold stress (0 °C and 5 °C) did not result in distinct changes in the expression of NbHsps in the CS, but a significant decrease in the HTAS. The expression of NbHsps further demonstrates that the HTAS has been acclimated to high temperatures. The results also determine that heat acclimation decreases cold tolerance in HTAS mites. This study reveals differences in the characteristics of heat and cold tolerance between the two strains of N. barkeri and provides useful information for future commercialization of N. barkeri for pest biological control, particularly the HTAS. Furthermore, it also describes high heat tolerance in HTAS at the molecular level.