Guocheng Fan

The Asian citrus psyllid (Diaphorina citri) serves as the principal insect vector responsible for the transmission of citrus Huanglongbing (HLB). Consequently, the effective control of D. citri is of paramount importance for curbing the spread of this devastating disease. Fir essential oil (FEO) exhibits a potent repellent activity against D. citri; however, its practical application is severely constrained by a short duration of efficacy arising from its high volatility. Imidacloprid (Im) is a conventional insecticide widely used for D. citri management, and prolonging its residual activity remains a critical challenge for field application. In this study, we synthesized dendritic mesoporous silica nanoparticles (DMSNs, ≈257 nm) and employed them to construct a nano-pesticide formulation co-loaded with both Im and FEO. Our results demonstrated that DMSNs possessed high loading capacities for Im (21.79%) and FEO (32.98%). Notably, both Im and FEO within the DMSNs-Im-FEO formulation exhibited favorable sustained-release profiles and significantly extended residual activities compared to their free counterparts. Furthermore, the DMSNs-Im-FEO formulation displayed preliminary non-target tolerance in citrus plants, Chinese milk vetch, and earthworms, indicating its low ecotoxicological risk. Overall, our study provides a novel and promising strategy for the sustainable management of D. citri, which holds considerable significance for the integrated management of HLB.

Boron (B) toxicity severely restricts Citrus growth and productivity in high-B soil and irrigation water environments. Although exogenous Zinc (Zn) has been reported to mitigate B toxicity in plants, the underlying physiological regulation mechanisms—particularly in Citrus—remain incompletely understood. In this study, seedlings of two Citrus species differing markedly in B tolerance—Citrus sinensis (sweet orange, B-tolerant) and C. grandis (sour pomelo, B-sensitive)—were subjected to three boric acid treatments (10, 200, and 400 μM) and five ZnSO₄ treatments (0.002, 0.05, 0.1, 0.2, and 0.25 mM) in a fully factorial design over 15 weeks. Comprehensive physiological assessments—including growth parameters, photosynthetic performance, mineral-nutrient profiling (in leaves and roots), and antioxidant enzyme activity—were conducted to decipher the mechanistic basis of Zn-mediated B detoxification. Results showed that 400 μM BA alone triggered severe B toxicity symptoms in the older leaves of C. grandis, whereas 0.25 mM Zn independently led to chlorosis symptoms similar to Fe deficiency in the apical leaves of both Citrus species. Either B or Zn toxicity affected photosynthesis in matured leaves. Exogenous Zn at 0.05–0.20 mM alleviated B toxicity symptoms in B-sensitive C. grandis, yet consistent alleviation of Zn toxicity by excess B was not observed across all measured variables. Severe B toxicity caused a significant reduction in Fe, N, P and Ca contents and a significant increase in Cu and Mn contents in C. grandis roots, yet it only led to a significant reduction in Mn, N, P and Ca contents in C. grandis leaves. Unlike this, B toxic treatments in C. sinensis resulted in a significant reduction in merely Fe content and a significant increase in Cu, Mn, N and K contents in roots, and a significant reduction in Mn and Ca contents in the leaves. Under basal B supply, 0.05–0.20 mM Zn supplementation dose-dependently increased root Zn, Cu and Mn contents as well as leaf Zn and Cu contents in both Citrus species, but concurrently decreased root Fe content and leaf Fe and Ca contents—additionally, in C. grandis, leaf N, P, K and Mg contents were further reduced. Regarding antioxidant responses in C. grandis, B toxicity significantly suppressed leaf CAT activity while enhancing APX and GPX activities. Under B toxicity conditions, 0.2 mM Zn supplement significantly restored CAT activity and suppressed APX and GPX activities. These antioxidant modulations were highly dependent on species identity and treatment combination, and were markedly more pronounced in B-sensitive C. grandis. Collectively, this work clarifies the physiological interplay between Zn and B in Citrus, uncovers divergent adaptive strategies employed by contrasting citrus species under combined B–Zn stress, and provides a mechanistic foundation for optimizing exogenous Zn application to mitigate B toxicity in citrus production.

Neonicotinoid insecticides (NIs) improve crop yield but raise environmental and health concerns. This review describes residues of 13 commercial NIs and their transformation products (TPs) in water, soil, air, vegetables, fruits, tea, and animal-derived foods. It also summarizes risks to nontarget organisms (aquatic species, soil invertebrates, and bees) and humans. NIs disrupt neuronal signaling in nontarget species, suggesting their ecological risks are substantially underestimated. Halogenated NIs show marked environmental persistence. Unexpectedly, all parent NIs and their TPs display high mobility. Six parent NIs and 70.45% of TPs show nontarget toxicity. Notably, 27.24% of neonicotinoid insecticide TPs (excluding dinotefuran’s TPs) simultaneously exhibit strong persistence, high mobility, and nontarget toxicity. These threats to ecosystems should not be overlooked. The review proposes forward-looking recommendations for next-generation NIs. Overall, this work provides critical insights into NIs toxicity and ecological impacts, offering valuable guidance for mitigating environmental contamination.

Nanozinc oxide (ZnO) is a known material for its high therapeutic efficacy against citrus canker. However, the influence of particle size on the antibacterial activity of nano-ZnO against Xanthomonas citri subsp. citri (Xcc), as well as the distinct bacterial response mechanisms to different nanoparticle sizes, remain poorly understood, limiting its broader application. In this study, differences in the antibacterial potentials of nano-ZnO particles with sizes of 30, 90, and 200 nm against Xcc were investigated. The results showed that the zeta potential of the three nano-ZnO variants displayed no significant differences. However, the antibacterial efficacy of nano-ZnO against Xcc was strongly dependent on particle size, with smaller particles exhibiting greater antibacterial activity. This is attributed to their increased capacity to damage bacterial cell membranes and DNA, which is linked to a higher generation of reactive oxygen species and greater release of Zn²⁺ within the bacterial cells. In addition, small-sized nano-ZnO exhibits superior efficacy in inhibiting biofilm formation, exopolysaccharide secretion, and xanthomonadin production in Xcc. Fourier transform infrared multivariate and two-dimensional correlation analyses revealed that macromolecular components in Xcc exhibited more pronounced responses to smaller-sized nano-ZnO particles, further supporting their superior antibacterial efficacy. In conclusion, this study provides valuable insights into the size-dependent antibacterial mechanisms of nanomaterials and offers a theoretical basis for the effective application of nano-ZnO in the control of citrus canker.

Azole and benzimidazole fungicides are widely used agrochemicals to prevent and treat fungal growth and are frequently detected in aquatic environments. Here, we aimed to assess the aquatic ecological risks of ten currently used azole and benzimidazole fungicides, which with the aryl hydrocarbon receptor (AhR) agonistic activity, and their transformation products (TPs). We obtained over 400 types of aerobic TPs for ten fungicides. Some fungicides and their TPs (approximately 26.7%) exhibited the potential AhR agonistic activity and toxicity to different aquatic species. Meanwhile, some compounds with the chlorine element and benzene ring structure exhibited environmental persistence and mobile ability. Several of them were frequently detected in aquatic environments, posing potential risks to aquatic ecosystems. These harmful fungicides and their TPs should be given attention. This study provides important insight into the aquatic ecological risks caused by azole and benzimidazole fungicides, which can provide theoretical guidance for their pollution control.

BACKGROUND: Diaphorina citri Kuwayama is the main vector of the Huanglongbing (HLB) pathogen Candidatus Liberibacter asiaticus ( C Las). Therefore, reducing C Las acquisition by D. citri is crucial for controlling the spread of HLB. RESULTS: This study aimed to investigate the effect of ZnO quantum dots (ZnO QDs) on C Las acquisition by D. citri . The results showed that ZnO QDs were absorbed by citrus plants and D. citri , inducing reactive oxygen species generation in the intestine and causing intestinal cell apoptosis. The uptake rate of C Las was reduced to 75% and 22.3% after treatment with 2 and 5 mg ∙ mL ⁻¹ ZnO QDs, respectively, compared with 100% in the control group. Transcription analysis showed significant changes in the expression of D. citri genes related to apoptosis, oxidative stress, and DNA replication and repair. CONCLUSION: The results suggested that ZnO QDs could efficiently reduce C Las acquisition by D. citri , providing a safe and reliable tool for HLB prevention and control. © 2024 Society of Chemical Industry.

BACKGROUND: Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is a devastating bacterial disease that reduces citrus yield and quality, posing a serious threat to the citrus industry. Several conventional chemicals have been used to control citrus canker. However, this approach often leads to the excessive use of chemical agents, can exacerbate environmental pollution and promotes the development of resistant Xcc. Therefore, there is significant interest in the development of efficient and environmentally friendly technologies to control citrus canker.RESULTS: In this study, water‐soluble ZnO quantum dots (ZnO QDs) were synthesised as an efficient nanopesticide against Xcc. The results showed that the antibacterial activity of ZnO QDs irradiated with visible light [half‐maximal effective concentration (EC₅₀) = 33.18 μg mL⁻¹] was ~3.5 times higher than that of the dark‐treated group (EC₅₀ = 114.80 μg mL⁻¹). ZnO QDs induced the generation of reactive oxygen species (•OH, •O⁻₂ and ¹O₂) under light irradiation, resulting in DNA damage, cytoplasmic destruction, and decreased catalase and superoxide dismutase activities. Transcription analysis showed downregulation of Xcc genes related to ‘biofilms, virulence, adhesion’ and ‘DNA transfer’ exposure to ZnO QDs. More importantly, ZnO QDs also promoted the growth of citrus.CONCLUSION: This research provides new insights into the photocatalytic antibacterial mechanisms of ZnO QDs and supports the development of more efficient and safer ZnO QDs‐based nanopesticides to control citrus canker. © 2024 Society of Chemical Industry.