Jabraeil Razmjou

Application of fertilizers can be a feasible strategy for enhancing plant defenses. This study was conducted to explore the impacts of biostimulants, including fulvic acid (FA) and Ascophyllum nodosum L. extract (AnE), along with NPK fertilizer and their combinations (FA + AnE, FA + NPK, AnE + NPK, and FA + AnE + NPK) on the physiological and biochemical traits of cucumber plants in uninfested and aphid (Aphis gossypii Glover)-infested conditions. Furthermore, the subsequent effects of these treatments on fitness parameters of A. gossypii were investigated. The results revealed that plants treated with FA + AnE + NPK treatment had the highest levels of enzymatic antioxidants and nonenzymatic antioxidants compared with the uninfested control plants. Following aphid infestation, total phenolic content and antioxidant enzyme activities significantly increased in all treatments. Photosynthetic pigment contents were higher in uninfested treated plants, while they significantly declined after aphid infestation. The scavenging activities of malondialdehyde, hydrogen peroxide, and DPPH (1,1-diphenyl-2-picrylhydrazyl) were differently affected under infested and uninfested conditions compared with the control. Biostimulant- and fertilizer-treated plants significantly affected the population of A. gossypii, with the lowest preadult survival, fecundity, r (intrinsic rate of increase), λ (finite rate of increase), and GRR (gross reproductive rate) recorded on FA + AnE + NPK-treated plants. Overall, the findings revealed that the studied treatments, particularly FA + AnE + NPK treatment can potentially be considered as a sustainable pest management strategy for increasing cucumber resistance to A. gossypii by altering plant traits and aphid fitness.

Green nanoparticle synthesis presents a sustainable agricultural approach that reduces dependence on chemical pesticides while promoting environmental sustainability. The whitefly (Trialeurodes vaporariorum), a major sap-sucking pest of tomato plants, causes significant yield losses worldwide. In this study, we developed an eco-friendly management strategy using zinc oxide nanoparticles (ZnO-NPs) biosynthesized from the brown seaweed Sargassum ilicifolium, a rich source of bioactive compounds. The nanosized ZnO-NPs (5-65 nm) were applied as a foliar spray and effectively mitigated whitefly-induced oxidative stress in tomato plants. Foliar application of ZnO-NPs at 50 ppm significantly increased chlorophyll a, chlorophyll b, and carotenoid contents compared to the control. This treatment also enhanced the activities of antioxidant enzymes, including superoxide dismutase, catalase, and phenylalanine ammonia-lyase. Additionally, ZnO-NPs at 50 and 100 ppm significantly reduced malondialdehyde and hydrogen peroxide levels. ZnO-NPs exhibited strong insecticidal activity against T. vaporariorum, achieving 96.66% mortality at 1000 ppm (LC₅₀ = 407.4 ppm after 96 h). ZnO-NPs synthesized using S. ilicifolium demonstrated a dual role: priming plant defense mechanisms and acting as an effective nanopesticide. These findings highlight their potential as a sustainable strategy for integrated whitefly management in greenhouse environments. Future research should focus on field-scale validation, environmental safety assessments, and formulation optimization.

This study evaluated the effects of ZnO and green-synthesized ZnO nanoparticles (ZnO-NPs) from Sargassum ilicifolium extract on the biochemical interactions between tomato leaves and the destructive pest Tuta absoluta. The average size and stability of ZnO-NPs were characterized using DLS, X-RD, and FE-SEM. Peaks in the FT-IR spectrum of the extract of the algae and ZnO-NPs, indicated the presence of carboxyl groups, amines, alkynes and alcohols. Treated tomato leaves exhibited increased total chlorophyll and anthocyanin contents, particularly at 100 and 50 ppm, compared to the control. A significant increase in total flavonoid content was observed at 100 ppm, while total phenolic content was also enhanced at 50 ppm. In T. absoluta larvae, exposure to 50 and 100 ppm ZnO-NPs led to a reduction in α-amylase, total protease, total protein, and TAG levels, alongside increased catalase activity. Additionally, G₆PD and ALT activities decreased at 50 ppm compared to the control. Lactate, MDA, and the RSSR/RSH increased at 100 ppm. Furthermore, ZnO-NPs at 50 and 100 ppm elevated larval aldolase activity, while AST and γ-GT activities declined. These findings indicate that ZnO-NPs enhance tomato defense mechanisms and mitigate larval damage, supporting their potential use in integrated pest management strategies against T. absoluta.

The citrus red mite, Panonychus citri (McGregor), can cause severe damage to citrus trees. Typhlodromips caspiansis Denmark & Daneshvar is an indigenous predatory mite that was recently reported in association with P. citri in the Northern provinces of Iran. This study aimed to investigate the bottom-up effect of potassium and salicylic acid on the development and life table parameters of T. caspiansis on P. citri reared under host-plant treatment. Two-year-old citrus seedlings were sprayed with a solution containing potassium fertilizer (0.02 g/L) plus salicylic acid (1 mM). The survival rate and duration of the immature stages of the predator, as well as the longevity of adults and fecundity, were recorded. There was no significant difference in the egg and larval duration of T. caspiansis fed on P. citri reared on potassium+salicylic acid-treated and untreated (control) citrus seedlings. In comparison to the control, the duration of deutonymph was prolonged by the application of this treatment. Also, the longevity of females that came from immatures under host-plant treatment. The net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) of T. caspiansis did not show significant differences between potassium+salicylic acid-treated and untreated citrus seedlings; while the mean generation time (T) differed significantly. It can be concluded from the previous study and the present study that the positive effects of potassium+salicylic acid on P. citri control entail no negative outcomes regarding predator fitness. However, further field-based studies are needed for more realistic conclusions.