Untreated Trees Research Articles

New evidence on the spread in Catalonia of the invasive longhorn beetle, Xylotrechus chinensis, and the efficacy of abamectin control.

The invasive wasp-mimicking Tiger Longicorn Beetle, Xylotrechus chinensis, a potentially lethal pest of mulberry trees (Moraceae: Morus spp.), was first reported in Europe in 2018. In Catalonia its spread has been impressive: one district, four towns, 44km2 in February 2018; four districts, 12 towns, 378km2 in July 2020; seven districts, 65 towns, 1134km2 in December 2023. It is likely the infestation will spread further in the future, in particular along the Mediterranean coast from Spain to Greece. The flight period of this beetle in Mediterranean countries is expanding on both ends (from the end of April to mid-October), probably due to increasing temperatures because of climate change, although this should be further proved. The adult beetle life span is 18-23 days in insectaria, likely somewhat shorter in the wild since they do not feed and spend more energy flying outside. The single treatment with abamectin carried out in a Catalonian town in June 2022 on a sample of 24 trees (12 treated, 12 untreated) has been effective in reducing the infestation of this beetle in relation to untreated trees. But the reduction was not complete since new exit holes appeared during the summer of the following year. Therefore, an additional treatment carried out during the first ten days of October should be tested to achieve a better control of this pest. It would also be worthwhile trying a single treatment of abamectin in mid-July since it should be able to kill larvae hatching before the treatment and still have sufficient residual activity for larvae hatching after the treatment, and thus cover the entire activity period. Also, to get satisfactory mulberry tree protection, it is likely that treatments might have to be repeated for a few consecutive years. Yearly re-infestations from untreated public and/or private mulberry trees are also a concern and make short-term control of this pest difficult, no doubt accounting for the rapid spread of this beetle.

Foliar Nourishment with Different Potassium Sources to Maximize Yield Through Improving Nutrient Uptake in Citrus Aurantifolia Trees Grown in Potassium-Deficient Soil

AbstractPurpose: Based on its crucial regulatory role in several biochemical processes, potassium (K) is considered to greatly influence fruit yield and quality. Methods: Two field experiments were carried out in two seasons (2021 and 2022) to explore the response of lemon (Baladi cv.) trees grown in K-deficient soil to four different K fertilizer sources applied individually as a foliar spray. K citrate (KC1 = 1.3 vs. KC2 = 2.6 g L− 1), K nitrate (KN1 = 1.5 vs. KN2 = 3.0 g L− 1), K tartrate (KT1 = 1.5 vs. KT2 = 3.0 g L− 1), and K thiosulfate (KS1 = 1.25 vs. KS2 = 2.5 g L− 1) were applied three times, and the treated trees were compared with untreated trees. This study was established with a randomized complete block design (RCBD) using four replicates. Results: The findings revealed that the KC treatment, regardless of dosage, showed clear superiority in terms of the values for the leaf phosphorus (%), manganese, and zinc contents (mg kg− 1), as well as fruit firmness, fruit dry matter, and total soluble solids in both seasons. In second place was the KT treatment, which yielded the best values for fruit length and width in 2021, the best values for leaf nitrogen and iron contents and fruit weight and volume in 2022, and the best values regarding variable fluorescence by maximum fluorescence, relative chlorophyll content (SPAD readings), the photosynthetic performance index, total acidity, and vitamin C in both seasons. Furthermore, the highest total lemon yield and leaf potassium contents were achieved with the KN treatment in both seasons. The heat map illustrating that most of the studied characteristics were positively and significantly correlated with total lemon yield (TLY). Conclusions: The KN treatment, closely followed by the KC treatment, is regarded to be the best treatment for most of the studied trails.

Temporal changes in the proanthocyanidins to anthocyanins ratio during dormancy associate with bloom time variations in peach

Our previous research demonstrated that fall applications of ethephon, an ethylene-releasing plant growth regulator, delay bloom in peach, accompanied by changes in endogenous hormones, ROS, sugar metabolism, and transcriptomic profiles during bud dormancy phases (endodormancy and ecodormancy). In this study, floral bud tissues were collected from ethephon-treated and untreated trees at three time points (200, 600, and 1000 chilling hours, CH) during endodormancy and two points (1000 and 3000 growing degree hours, GDH) during ecodormancy. Using ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF/MS), we aimed to unravel the untargeted metabolic changes explaining ethephon-mediated bloom delay. Metabolite set-enrichment analysis (MSEA) revealed significant chemical group variations between dormancy phases, with a threefold increase in flavonoids during endodormancy and a doubling of organic and amino acids during ecodormancy. Further analysis of genes associated with the biosynthesis and transcriptional regulation of the flavonoid pathway showed that ethephon treatment upregulated genes associated with proanthocyanidin (PA) biosynthesis and downregulated genes related to anthocyanins (ACNs). We quantified PA and ACN contents in 12 peach cultivars with contrasting bloom times and chilling requirements (e.g. 727–1308 CH). Late-bloom cultivars had higher PA levels during endodormancy, while early-bloom cultivars had higher ACN levels during ecodormancy. Staining buds with 4-dimethylaminocinnamaldehyde (DMAC) dye revealed a decline in the PA/ACN ratio at later ecodormancy stages, correlating with bloom time. Integrated analysis of metabolite content and gene expression in late-bloom 'KV021779' and early-bloom 'John Boy' cultivars validated that late-blooming cultivars have higher PA levels during endodormancy, extending dormancy-release periods and resulting in later blooms.

Pear performance as affected by the application of some nano fertilizers in combination with biochar as a biostimulant under drought conditions

Drought is an environmental stress that can negatively influence growth and productivity of fruit trees because it decreases the photosynthetic rate and stomatal conductance and raises the rate of water loss from the plant surfaces. Therefore, this study investigated the soil application of biochar individually or in combination with the spraying of boron, silicon, and molybdenum relative to the growth attributes, fruit drop percentages, yield, and fruit quality of Le Conte pear trees grown under drought stress. The trees were fertilized by biochar at 0, 1, and 2 kg per tree individually or in combination with the foliar spraying with 0 mg B2O3 + 0 mg SiO2 + 0 mg MoO2, 10 mg B2O3 + 25 mg SiO2 + 25 mg MoO2, 20 mg B2O3 + 50 mg SiO2 + 50 mg MoO2 and 30 mg B2O3 + 75 mg SiO2 + 75 mg MoO2 at start of February, start of March and start of April, compared to untreated trees (control). The results showed that the soil addition of biochar or spraying of nano fertilizers individually or in combinations improved the vegetive growth, productivity and fruit quality, and leaf mineral content, meanwhile they reduced the fruit drop. The best results were obtained by the application of 2 kg biochar combined with 30 mg B2O3 + 75 mg SiO2 + 75 mg MoO2, which was superior to other applied treatments in the two seasons.

Impacts of phosphite treatment on Phytophthora community assemblages and inoculum abundances in Phytophthora-infected forest soil

Phytophthora are causing declines in forest tree species worldwide and the chemical control treatment, phosphite, is the only treatment consistently shown to provide some protection to natural ecosystems from Phytophthora diseases. Phosphite inhibits Phytophthora growth and sporulation whilst boosting defence responses in the plant host. It is unclear, however, the extent of the impact of phosphite on Phytophthora species assemblages and inoculum abundances in soil around trees following treatment within natural ecosystems. In New Zealand, kauri (Agathis australis), an endemic and threatened foundation species, suffers from a dieback disease primarily caused by Phytophthora agathidicida. Phosphite is applied by trunk injection to kauri and has been shown to improve resin ‘bleed’ symptoms from basal trunk lesions and to promote recovery of thinned canopies. Phytophthora community and inoculum abundance were investigated in response to phosphite treatments at two field sites (Huia and Waitoki) in infected kauri stands in Auckland, New Zealand. At Huia, soil sampling and tree health surveying were conducted in November 2023 on trees treated with phosphite in 2012 as part of an earlier study. At Waitoki, the response to phosphite treatment was monitored 6 and 18 months following treatment. Phytophthora species were detected using soil baiting and metabarcoding of environmental DNA (eDNA) from soil and quantified with qPCR of root and soil DNA. Three species were detected with soil baiting (P. agathidicida, P. cinnamomi, and P. multivora) and two additional species with metabarcoding (P. pseudocryptogea, and an unknown clade 7 species similar to P. europaea). Phytophthora cinnamomi was the most abundant species, followed by P. agathidicida. Both species were more likely to occur together than by chance alone and were associated with declining tree health. The P. europaea-like species was in approximately 50% of the samples and was less likely to occur in roots with poorer health, or in association with P. agathidicida. The abundance of P. agathidicida inoculum was lower in the soil around the phosphite-treated trees than around the untreated control trees 1.5 years after treatment at Waitoki. Phosphite halted the lateral expansion of basal resin bleeds, and resin viscosity was reduced. Not only did phosphite treatments improve kauri dieback symptoms, but the phosphite treatments potentially had a direct impact on the epidemiology of the disease by reducing inoculum load around treated trees, with direct implications for disease management as an effective way to protect uninfected areas and minimise the spread of inoculum from infested zones.

The Role of Some Biostimulants in Improving the Productivity of Orange

One of the environmental problems that affects negatively orange productivity is drought because it greatly minimizes the growth attributes, photosynthetic process, water uptake, percentage of fruit set, and productivity; meanwhile, it raises the rates of respiration and transpiration, as well as the premature and preharvest fruit drop percentages. In addition, drought creates osmotic stress, affects the relationship between plants and water, reduces the amount of water in shoots, and prevents plant cell development and expansion. It is very important to search for a solution to minimize the effect of drought stress; therefore, the present study has investigated the effect of the application of humic acid (HA) at 0, 1 and 2 kg per tree and spraying of seaweed extract (SWE) at 0.2, 0.3 and 4% in combination with moringa leaf extract (MLE) at 2, 4 and 6%, respectively, on the productivity, fruit quality and nutritional status of navel orange cv. Washington during the 2022 and 2023 seasons. The results proved that the application of the biostimulants individually or in combination significantly positively changed the vegetative growth, productivity, fruit quality parameters and leaf mineral content of macro- and micronutrients of the treated trees compared to untreated trees. The superior treatments which gave the best results were 2 kg HA + 0.4% SWE + 6% MLE followed by 2 kg HA + 0.3% SWE + 4% MLE over the rest of the applied treatments.

Control of Mal secco disease in lemon by drip irrigation with fungicide

Mal secco disease of citrus is caused by the mitosporic ascomycete fungus Plenodomus tracheiphilus (formerly Phoma tracheiphila [Petri]). Mal secco is a highly destructive vascular disease of lemon and other citrus which is presently confined to the Mediterranean basin and has a marked economic impact on the citrus industry. The fungal pathogen infects the host tree by penetrating through wounds in the roots or canopy. Infection spreads quickly into the main branches and trunk and tree mortality usually ensues. The most typical symptoms are veinal chlorosis, leaf wilt, red discoloration of the xylem and dieback of twigs and branches. Current accepted control of the disease is mainly by sanitation of infected wood, and copper application during the winter to prevent germinating spores from infecting the plant. No effective chemical control for this disease has been reported. We present a drip-irrigation protocol to protect trees and control the disease in which we apply 250 g/ha of the triazole fungicide flutriafol five times a year. Progression of disease symptoms in the treated trees was inhibited by up to 81% compared to the untreated control, thereby significantly shortening the sanitation process and making it less costly than in untreated trees. Moreover, disease symptoms became less severe as the duration of treatment increased. We have treated orchards for 3 years, and present an effective commercial protocol for the growers which will help them control Mal secco disease.

Действие органоминерального комплекса «Белый Жемчуг» на качество и выход товарных плодов яблони после длительного хранения

Biological fertilizers improve fruit quality; for instance, organomineral, or activated mixes are known to increase consumer qualities of apples. This article describes the effect of a new activated complex (non-root treatment) on the yield, chemical composition, and physiological disorders, e.g., scald and brown spot, of commercial apples after long-term storage. The research featured the natural activated complex of the Beliy Zhemchug (White Pearl) brand. The apple trees were divided into two groups: 1 – untreated control trees; 2 – trees that underwent a non-root treatment with the activated complex (1% solution of its Antifreeze variant + 1% solution of the Drip Ca + Mg variant). The trees belonged to the Sinap Orlovskiy cultivar, which is highly susceptible to brown spot and scald, both in the orchard and during long-term storage. The apples were studied for chemical composition and consumer qualities after long-term storage in a CV114-S refrigerator at +2°C and a relative humidity of 85–90%. The non-root treatment of apple trees with the Beliy Zhemchug activated complex had no significant effect on the content of soluble solids, total sugars, titrated acids, and ascorbic acid in ripe apples. Weather conditions affected the chemical composition 30 days before harvesting. The non-root treatment increased the yield of commercial apples by 1.62 times after long-time storage. The scald, brown spot, and moniliosis damage decreased by 1.9, 2.6, and 1.9 times, respectively. The activated fertilizers of the Beliy Zhemchug brand proved highly efficient as additional techniques in common apple cultivation and could be recommended to improve the quality and yield of commercial fruits after long-term storage.

An Environmentally Friendly Method to Protect Box Trees (Buxus spp.) from Attacks by the Invasive Moth Cydalima perspectalis

The non-native invasive box-tree moth Cydalima perspectalis causes severe damage to ornamental box trees (Buxus spp.) and natural boxwood stands. So far, no promising natural enemy of C. perspectalis has been discovered in Europe. Many garden owners would like to protect their box trees from C. perspectalis without the use of insecticides, which also harm other arthropod species. In a controlled experiment under natural conditions, we tested whether box trees covered with a net during the flight period of C. perspectalis are as well protected against the moth as trees treated with a bioinsecticide. After 1 year, the box trees covered with a net during the moths’ flight activity (monitored by light traps) showed no damage by larvae (average loss of leaves 0%), as did box trees regularly treated with a bioinsecticide (control group 1). In contrast, box trees with no protection (untreated box trees; control group 2) lost 97.7% of their leaves due to larval feeding. In a second experiment, we investigated whether defoliated box trees can recover when covered with a net during the flight period of the moth. Protected by the net, the emerging new leaves were not attacked by C. perspectalis. After 1.5 years, the trees had 24% of their original foliage again. Our study demonstrates that temporarily covering box trees with a net protects them against damage by C. perspectalis in an effective way.

Homobrassinolide Delays Huanglongbing Progression in Newly Planted Citrus (Citrus sinensis) Trees.

Huanglongbing (HLB), or citrus greening, is a devastating disease impacting citrus trees worldwide, with severe effects particularly noted in Florida. Current strategies to combat HLB focus on aggressive replanting, despite the high susceptibility of young trees to infection. In this context, it is critical to explore agronomic practices that can enhance the health and resistance of young citrus trees to HLB. Here, we demonstrate that treatment with homobrassinolide (HBr), a type of brassinosteroid, in newly planted citrus (Citrus sinensis) trees can delay HLB infection and improve tree health amidst the high psyllid pressure conditions endemic to Florida. Our study reveals a significant reduction in HLB infection rates in HBr-treated trees compared to control trees, with only 25% of treated trees testing positive for HLB by six months, in contrast to 100% infection in untreated trees. This delay in infection may be attributed to HBr inducing an immune response and negatively impacting psyllid performance, as subsequently demonstrated in a greenhouse experiment. Our findings suggest that HBr applications could serve as a viable strategy to enhance the resilience of citrus production against HLB, underscoring the need for further investigation into their mechanisms of action and potential role in a comprehensive pest and disease management strategy.

Effect of collection period on oleoresin yield of Pinus merkusii

Pinus merkusii is one of the most important timber species in Indonesia, the main product of which is its oleoresin. The objective of this study was to examine the effects of collection period (three periods, with 6-day observation each) on oleoresin yield in relation to two factors: growth sites of Pinus merkusii, which in the case of this study were East Banyumas, West Banyumas, and West Pekalongan Forest Management Units, and use of stimulants (sulfuric acid and ethephon mixtures, ETRAT, SR4, and no treatment). The average total oleoresin yield from a single tree or wound during the 18-day observation period was 110-185 g/tree for untreated trees and 159-442 g/tree for stimulant-treated trees. By analysis of variance, the interaction between each collection period (6-day observation period) and tree growing sites showed that the maximum average oleoresin yield for one hole was 109.32 g/tree measured in East Banyumas in the first collection period. Furthermore, the East Banyumas site consistently showed significantly the highest yield in each period. The interaction between the factors of stimulant and collection period (6-day observation) resulted in the highest average oleoresin yield (121.86 g/tree) measured for trees treated with sulfuric acid (20%) and Ethephon (2%) mixtures in aqueous solution (v/v) treatment in the first collecting period. In West Pekalongan, the resin yield from trees treated with different treatments tended to be positively related to tree diameter. In addition, a positive correlation was found between resin yield and tree height or crown closure, while a negative correlation was found between resin yield and site elevation in trees treated with certain stimulants.

Effect of Different Water-Retaining Agents and 1-Aminobenzotriazole Rooting Powder on the Survival of Ornamental Tree Transplants

Tree transplanting has become a crucial technical tool in both national afforestation projects and the development of garden greening. The demand for creating green ecological urban environments has significantly increased with the development of modern urbanization and improved living standards. Consequently, there is an increasing need for ornamental trees in urban construction. Ensuring higher survival rates in tree transplantation technology is of utmost importance. Given that temperature strongly influences tree growth, it is imperative to investigate how different water-retaining agents (WRAs) and 1-aminobenzotriazole (ABT) rooting powder impact the survival rate of transplanted ornamental trees. After transplantation, ornamental trees were subjected to varying dosages of WRAs and concentrations of ABT rooting powder, and their cold tolerance (CT) was evaluated using the conductivity method and growth test. The results revealed that the application of rooting powder significantly enhanced the CT of willow trees by 24.4%, 14.7%, and 30.2% in September, December, and March, compared with untreated ones. For the same months, the CT of magnolia trees increased by 57.4%, 23.7%, and 16.8%. Additionally, during those months, the CT of cypress trees treated with WRAs showed remarkable improvement, increasing by 108.9%, 108.9%, and 108.9%, respectively, with enhancements of 6.6% and 27.3% compared to untreated cypress trees. These findings highlight the crucial importance of investigating the impact of various WRAs and ABT rooting powder on the survival rate of transplanted ornamental trees, establishing a crucial benchmark for future advancements in this domain.

Enhancing productivity, modifying biochemical parameters, and regulating the phenylpropanoid pathway in 'Le-Conte' pears through optimal protocatechuic acid treatments

BackgroundThis study aimed to investigate the impact of protocatechuic acid (PRC) treatments on the productivity and fruit quality of 'Le-Conte' pears, with a specific focus on productivity, stone cells content, and antioxidant activity. The research spanned over three consecutive cultivating seasons, with the first season serving as a preliminary study to determine the optimal PRC concentrations and the most effective number of spray applications. During the initial season, response surface methodology (RSM) was employed to optimize PRC concentration and application frequency. PRC was evaluated at concentrations ranging from 50 to 400 ppm, with treatment frequencies of either once or twice. Considering the optimal conditions obtained from RSM results, PRC treatments at 200 ppm and 300 ppm were applied twice, and their respective effects were studied in comparison to the control in the following seasons.ResultsRSM results indicated that PRC at 200 and 300 ppm, applied twice, once during full bloom and again three weeks later, yielded the most significant effects. Subsequent studies revealed that PRC treatments had a substantial impact on various aspects of fruit production and quality. Applying 300 ppm PRC once during full bloom and again three weeks later resulted in higher fruit set percentages, lower fruit abscission, and enhanced fruit yield compared to untreated trees. Additionally, the 200 ppm PRC treatment maintained physicochemical characteristics such as fruit color, increased total soluble solids (TSS), and total sugar, and maintained higher ascorbic acid content and antioxidant capacity in the fruits while reducing stone cells content and lignin. Notably, enzyme activities related to phenylpropanoid metabolism and stone cells, including phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-Coumarate-CoA Ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and cinnamoyl-CoA reductase (CCR), as well as peroxidase, polyphenol oxidase, and laccase, were significantly regulated by PRC treatments.ConclusionOverall, this study suggests that PRC treatments are suitable for enhancing pear yield and quality, with PRC at 200 ppm being the more recommended option over 300 ppm. This approach serves as an effective strategy for achieving a balance between enhancing the productivity and fruit quality of 'Le-Conte' pears.

Effect of rock phosphate and bacteria solubilizing nutrients soil application on yield and fruit quality of olive trees cv. “Picual” under the arid zones

This study was carried out throughout two seasons and Located in a private olive grove on Cairo-Ismailia Desert Road in Egypt. The aim of this experiment was to use different amounts of rock phosphate (1, 2 or 3 kg/tree) with different time of additions (2 or 3 times) for phosphorous and sulfur release bacteria to form 6 treatments beside the control (untreated trees) on the mineral contents of the leaves, the vegetative growth, the yield, and the quality of the fruit of Picual olive trees planted in sandy soil and watered with drip irrigation for two seasons. The outcomes demonstrated that application of 2 or 3 kg rock phosphate per tree for two or three times of phosphorus and sulfur release bacteria gave the highest yield and improves fruit quality. Generally, the treatment of 2 kg rock phosphate for three times of P and S release bacteria is recommended due to its clear effect among all treatments on the abovementioned parameters.

Erwinia amylovora Type III Secretion System Inhibitors Reduce Fire Blight Infection Under Field Conditions.

Fire blight, caused by Erwinia amylovora, is an economically important disease in apples and pears worldwide. This pathogen relies on the type III secretion system (T3SS) to cause disease. Compounds that inhibit the function of the T3SS (T3SS inhibitors) have emerged as alternative strategies for bacterial plant disease management, as they block bacterial virulence without affecting growth, unlike traditional antibiotics. In this study, we investigated the mode of action of a T3SS inhibitor named TS108, a plant phenolic acid derivative, in E. amylovora. We showed that adding TS108 to an in vitro culture of E. amylovora repressed the expression of several T3SS regulon genes, including the master regulator gene hrpL. Further studies demonstrated that TS108 negatively regulates CsrB, a global regulatory small RNA, at the posttranscriptional level, resulting in a repression of hrpS, which encodes a key activator of hrpL. Additionally, TS108 has no impact on the expression of T3SS in Dickeya dadantii or Pseudomonas aeruginosa, suggesting that its inhibition of the E. amylovora T3SS is likely species specific. To better evaluate the performance of T3SS inhibitors in fire blight management, we conducted five independent field experiments in four states (Michigan, New York, Oregon, and Connecticut) from 2015 to 2022 and observed reductions in blossom blight incidence as high as 96.7% compared with untreated trees. In summary, the T3SS inhibitors exhibited good efficacy against fire blight.

Performance of Mango Trees under the Spraying of Some Biostimulants

Ensuring the sustainability of horticultural production is crucial to meeting consumer demand, and the most effective approach involves enhancing the efficient utilization of resources to support the production of wholesome foods. Plant biostimulants are substances defined by their ability, when applied to plants or the rhizosphere, to enhance root development, resulting in heightened vigor. They facilitate the more effective uptake and translocation of nutrients and water throughout the growing season. Additionally, these biostimulants contribute to improved plant health and quality by supplying essential nutrients that stimulate overall growth and metabolic processes. Therefore, this study was performed to examine the impact of some biostimulants on the possibility of improving vegetative growth, yield, fruit quality, and the leaf mineral content of mango cv. Keitt. Mango trees were sprayed with Putrescine at 25, 50, and 100 mg/L; Brassinosteroids at 0.5, 1, and 2 mg/L; and Chitosan at 500, 1000, and 1500 mg/L four times starting from mid-April, with three-week intervals during the seasons of 2021 and 2022. The results showed that the foliar application of these three biostimulants improved the growth, yield, and fruit quality of mango trees as opposed to untreated trees during two study seasons. The results also showed that the foliar application of 1500 mg/L of Chit, 2 mg/L of Brs, and 100 mg/L of Put gave the highest increments for inducing the number, length, and thickness of shoots, leaf area, and leaf chlorophyll over the other applied treatments. In addition, it also heightened the fruit set, fruit yield, and the fruit’s physical and chemical characteristics in both experimental seasons.

Concrete of Treated and Untreated Date Palm Tree Wastes

Concrete of Treated and Untreated Date Palm Tree Wastes

Influence of Spraying Some Biostimulants on Yield, Fruit Quality, Oil Fruit Content and Nutritional Status of Olive (Olea europaea L.) under Salinity

Salinity currently affects more than 20% of agricultural land and is expected to pose potential challenges to land degradation and agricultural production in the future. It is a leading global abiotic stress that affects general plants and cultivated crops adversely. The utilization of biostimulants can enhance the efficiency of plant nutrition, facilitate the uptake of nutrients, boost crop yield, improve the quality characteristics of fruits and enhance plants’ ability to withstand abiotic stresses. Biostimulants serve as a vital reservoir of macro- and microelements and plant hormones, such as auxins, cytokinins and gibberellins. Therefore, the current study was conducted to examine the effect of the foliar application of some biostimulants on relieving the side effects of salinity on olive trees (Olea europaea) cv. Kalamata. The olive trees were sprayed three times with moringa leaf aqueous extract (MLE) at 2, 4 and 6%, seaweed extract (SWE) at 1000, 2000 and 3000 ppm and their combinations: 2% MLE + 1000 ppm SWE (combination 1), 4% MLE + 2000 ppm SWE (combination 2) and 6% MLE + 3000 ppm SWE (combination 3). The results revealed that the application of biostimulants had a beneficial effect on the overall growth and development of olive trees, surpassing the performance of untreated trees. Spraying MLE and SWE, particularly at concentrations of 6% and 3000 ppm, respectively, significantly enhanced various aspects of olive tree performance. Notably, there were significant increases in leaf chlorophyll content, flower number, fruit set percentages, fruit yields, fruit oil content, fruit firmness, total soluble solid (TSS) percentage and leaf macro- and micronutrients. Furthermore, the combined application of MLE and SWE resulted in a greater effect when compared to using each one individually. In both seasons, combination 3 outperformed the other treatments that were applied.

Use of Gibberellic Acid to Improve Health and Productivity of HLB-Affected ‘Valencia’ Trees

The goal of this publication is to provide the latest gibberellic acid (GA) use recommendation to Florida citrus growers. Recently, a multiyear field trial conducted on ‘Valencia’ has shown that GA applied monthly from September to January can improve yield of HLB-affected trees on average by 30% compared to untreated trees. Although GA treatment cannot eradicate the pathogen that causes HLB in affected citrus trees, the current GA application recommendation can provide growers an alternative remedy to alleviate HLB symptoms and ameliorate the production issues that are associated with the disease, including yield decline, reduced fruit size, increased preharvest fruit drop, and rapid tree health decline, until a cure for HLB or complete HLB-resistant cultivars can be developed. Written by Tripti Vashisth, and published by the UF/IFAS Horticultural Sciences Department, April 2023.

Application of an Exhausted Fermentation Broth Obtained from Biohydrogen Production in an Apple Orchard: Assessment of Fruit Quality

About 95% of global hydrogen production is made by fossil fuels using different technologies which are all characterized by high energy consumption and high carbon emissions. Alternatively, more sustainable production methods, such as biological fermentation processes, are under study. Dark fermentation, also called acidogenesis, entails the transformation of a great variety of organic substances into a mixture of organic and inorganic products, as well as gases (H2 and CO2). In this study we tested an exhausted fermentation broth, derived after Clostridium fermentation for H2 production, as a biostimulant via foliar application in an intensive apple orchard. Two different doses were applied upon dilution of the broth in water (100 mL L−1 and 10 mL L−1), evaluating the main fruit quality parameters (fresh weight, fruit diameter, dry matter, firmness, soluble solid content, color lightness, DA index) in addition to macro- and micro-nutrients and heavy metals concentrations. Chemical characterization of the broth showed a high amount of low-MW polypeptides (Trp-Glu-Lys, Ile-Pro-Ile, Phe-Pro-Lys, His-Pro) and organic acids (formic acid, butyric acid, butanedioic acid); moreover, quantitative analyses of inorganic ions showed no heavy metal detection but high concentrations of nitrogen, phosphorus and potassium, compatible with use in agriculture. The fruit quality parameters showed significantly higher mean fruit weight compared to the untreated trees, as well as higher dry matter. No statistical differences were recorded among the treatments for fruit firmness, diameter and yield. Soluble solids content in both treatments were significantly lower than the controls, whereas the DA index mean values were higher in both treatments compared to the controls, indicating a delay in fruit ripening probably due to the high nitrogen broth concentration. Regarding the chemical analyses of fruits, no particular differences were found among the treatments, except for Fe, which showed a significantly higher amount upon treatment with the lower dose. As concerns leaves, no phytotoxic symptoms were detected in both treatments, making the described exhausted broth a candidate for its use as a plant biostimulant. Additional studies are needed to evaluate the ideal application dose, identify further action targets and implement appropriate strategies to concentrate the biostimulant active compounds.