Foliar Application of Biostimulants to Improve Growth, Yield and Fruit Quality of ʻValenciaʼ Orange Trees Under Deficit Irrigation Conditions

Foliar sprays with synthetic biostimulants or microbial biostimulants PGPR (plant growth promoting rhizobacteria) were used . They contain amino acids, macro and micro elements, humic acid and vitamins . Also its direct effect in release stimulants, nutrients, antibiotics, biosides and sidrofores or activation of these microorganisms in plant rhizosphere in activation and improving plant growth. This study was carried out during 2013 and 2014 seasons on 10 years old Washington navel orange (Citrus sinensis Osbeck) trees budded on sour orange (Citrus aurantium L.) rootstock, grown in a private orchard located at Motobus, Kafr El Sheikh Governorate, to study the effect of synthetic stimulants (Furdose) and microbial biostimulant (Azospirillum lipoferum )on fruit set, dropping, yield and fruit quality. Furdose as a commercial synthetic biostimulant and microbial biostimulant Azospirillum lipoferum were used as foliar application alone or in combination at two stages, before flowering(first mach) or after fruit set(first may) or before flowering and after fruit set. The obtained results revealed that, fruit set and drop percentages, yield and fruit quality were u significantly affected by Furdose and Azospirillum lipoferum treatments alone or in combination in both seasons . The data cleared that, both stimulators enhanced fruit set percentage, yield and fruit quality of Washington navel orange trees . Azospirillum lipoferum alone or combined with Furdose was more effective on improving the productivity and fruit quality .The T6 (foliar spray of A. lipoferum after fruit set), T7 ((foliar spray of A. lipoferum before flowering and after fruit set) and T10 (foliar spray of Furdose plus A. lipoferum before flowering and after fruit set) were the most effective treatments on yield and fruit quality. It increased fruit set, yield and fruit quality in terms of fruit number, fruit kg/tree, fruit firmness, soluble solids content, reducing and total sugars and vitamin C. Fruit drop was decreased without significant differences among them in both seasons. Thus spraying with Azospirillum lipoferum after fruit set T6 ( foliar spray of A. lipoferum after fruit set) ) gave 112.4 and 115.7 kg/tree compared with T7 (foliar spray with Azospirillum lipoferum before flowering and after fruit set) 108.7 and 121.4 kg/tree and T10 ((foliar spray the combination of them before flowering and after fruit set) 114.7 and 130.3 kg/tree during both seasons, respectively . The use of ( Azospirillum lipoferum ) is recommended for increasing fruit yield and quality such as firmness, SSC, V.C and total sugars which may be increase the fruit ability to handling stages and longest shelf life, and gave the highest of net return per feddan and the increase in net return over control. when used alone or with synthetic biostemulants ( Furdose) compared with the use of synthetic biostemulants ( Furdose) alone .

Supplemental foliar applied mixture of amino acids and seaweed extract improved vegetative growth, yield and quality of citrus fruit

This part of the investigation studied the effect of foliar spraying with urea (0.5%); a mixture of Zn (0.4%), Mn (0.3%), Fe (0.5%), and Cu (0.3%) in sulphates (from 23% Zn, 28% Mn, 19% Fe, and 30% Cu, respectively); and two growth regulators (GA3 at 25 ppm and α-NAA at 10 ppm); as well as number and date of sprays on fruit pedicel pectin content, some flowering aspects, and fruit set and drop percentages. Applying urea, micronutrients, or both significantly increased pectin content in the pedicels of the attached and dropped fruit. The treatment including urea plus micronutrients resulted in the highest values for pectin in fruit stem. Either GA3 or NAA significantly raised pectin content over that of the water-sprayed control. However, NAA was more effective in increasing pectin content in fruit pedicel. The overall treatment including urea and micronutrients with GA3 or NAA was the most effective in producing the highest percentage of leafy inflorescence in 1991–92 and 1992–93 seasons. Any nutrition treatment was significantly effective in increasing fruit set and reducing fruit drop compared with the water-sprayed control; however, the treatment including all sprayed nutrients was the most effective. Application of GA3 or NAA significantly increased fruit set percentage and reduced June and preharvest fruit drop; however, NAA was more effective in reducing fruit drop than GA3.

The kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang & A.R. Ferguson] has attained significant importance for commercial cultivation in the mid-Himalayan region of the Indian subcontinent during the last three decades. The fruit quality matching international standards has remained a concern. Keeping in mind the bio-stimulatory effects of seaweed extract, a marine bioactive component in horticultural crops, the current study conducted to elucidate the impact of seaweed extract on kiwifruit growth, yield, and quality was conducted in the Department of Fruit Science’s kiwifruit block at Dr. Yashwant Singh Parmar University of Horticulture and Forestry, Nauni, Himachal Pradesh, India. For the studies, nine-year-old Allison kiwi vines of uniform size and vigor were planted at a spacing of 4 m × 6 m. With 11 treatments, the experiment was set up in a randomized block design viz, T1: Spray treatment of 1000 ppm (seaweed extract) SWE at fruit set (FS); T2:Spray treatment of 2000 ppm SWE at FS; T3: Spray treatment of 3000 ppm SWE at FS; T4: Spray treatment of 1000 ppm SWE at FS and 10 days after Fruit set (FS); T5: Spray treatment of 2000 ppm SWE at FS and 10 days after FS (DAFS); T6: Spray treatment of 3000 ppm SWE at FS and 10 days after FS; T7: Fruit dip treatment of 1000 ppm SWE at 10 days after FS; T8: Fruit dip treatment @ 2000 ppm SWE at 10 days after FS; T9: Fruit dip treatment @3000 ppm SWE at 10 days after fruit set; T10: Fruit dip treatment @ 5 ppm CPPU at 10 days after fruit set; T11: Control. The current study compared several seaweed extract treatments, which were applied at various times and concentrations, to N-(2-chloro-4-pyridyl)-N-phenyl-urea (CPPU-5ppm) and untreated control. Seaweed extract (SWE) dip at 3000 ppm 10 days after the fruit set produced significant growth in fruit length and diameter in growing kiwifruit, which was non-significant with CPPU treatment and superior to control. The shape index, fruit weight, and total fruit yield were also found to be the highest with the same treatment. Fruit quality parameters, namely fruit soluble solids contents (SSC) and total sugars, were recorded at a maximum with the SWE Spray dose of 3000 ppm at FS and 10 DAFS. The SSC: Acid ratio and reducing sugars were recorded as the highest with an application of SWE dip at 3000 ppm 10 DAFS. The application of SWE dip at 2000 ppm 10 DAFS) was found to advance the harvesting maturity by 6 days and also exhibited the lowest physiological loss in weight (% PLW) with the highest ascorbic acid content. After 15 days of storage at ambient room temperature (25 ± 2 °C), the application of SWE dip at 3000 ppm 10 DAFS recorded the highest SSC acid ratio and the lowest titratable acidity. Thus, the application of seaweed extract dip at 3000 ppm 10 days after the fruit set can be recommended to the farmers as an appropriate alternative to the chemical treatment.

Correlation of Diplodia (Lasiodiplodia theobromae) infection, huanglongbing, ethylene production, fruit removal force and pre-harvest fruit drop

Sixteen-year-old navel orange trees at a private orchard located in Kafer El-Sheikh Governorate, Egypt, were used in this study. Compost tea (CT) and filtrate biogas slurry liquid (FLB) were applied at two different concentrations (50% and 100%); control trees were sprayed with water. Trees treated with CT at 100% were the highest in yield, fruit weight, and vitamin C, whereas the highest percentage of fruit set, fruit number, and soluble solid content (SSC), lowest fruit drop, and highest reducing and total sugars were in trees treated with 100% FLB. Concentrations at 50% for both foliar application (CT and FLB) improved yield and fruit characteristics than control treatment. Generally, using a foliar application of compost tea and filtrate biogas slurry liquid at (100%) treatments as food nutrients could be recommended to improve the yield and fruit quality of navel orange fruits under the current study conditions. Implications: Consequently from the previously mentioned results, it was clear the great role of compost tea (CT) and filtrate biogas slurry liquid (FLB) as two sources of foliar application of organic fertilization for Washington navel orange grown in a clay loamy soil, as they are indispensable for improvement of the nutritional status of the navel orange trees and production of maximum yield and quality of orange, as well as minimizing the cost of production and in turn increasing the income of orange orchard. So, it should be recommended the superiority of application of FLB and CT, especially 100%, which gave the best results in yield and physical and chemical characteristics of navel orange fruits.

This work conducted to investigate the effect of NAA and CPPU on fruit set and retained/panicle, accumulative and relative fruit drop %, fruit quality and yield, changes in total soluble sugars on Bacon avocado (Persea Americana Mill.) trees. The selected trees were foliar sprayed twice, at full bloom and beginning of fruit set, with one of the following treatments, water (control), NAA at 15 or 30 ppm, CPPU at 5 or 10 ppm, and their combinations. Avocado trees treated with 30 ppm NAA + 5 ppm CPPU resulted in the highest fruit set/panicle, fruit retained/panicle and significantly reduced the peak of fruit drop happen 2 weeks after fruit set. Also, 30 ppm NAA + 5 ppm CPPU and 5 ppm CPPU produced the highest fruit weight, fruit dimension and yield. All the treatments with NAA or CPPU significantly decreased the content of total soluble sugars in the leaves from the 3rd to 8th weeks after fruit set and starch from the 1st to 3rd week after fruit set. Based on this study, NAA and CPPU promoted the mobilization of carbohydrate from the leaves to the fruitlet. Hence, NAA or CPPU suppressed fruit drop in avocado by increasing the availability of carbohydrate in fruitlet and thus improved fruit retention.

To decrease fruit abscission, increase yield and improve fruit quality of Santa Rosa (Prunus salicina Lindl.) plum; amino acids (AA), naphthalene acetic acid (NAA) and naphthalene acetamide (NAD) and a combination of them were applied at different concentrations; at full bloom stage and one week after fruit setting stage during 2015 and 2016, in a private orchard at Ashmoun, Monofia governorate, Egypt. Results indicated that fruit set percentage significantly increased by all AA, NAA and NAD treatments compared to the control. AA 0.25 ml/L+NAA 10 ppm + NAD at 10 ppm recorded the highest significant fruit set percentage and the lowest significant fruit drop percentage and gave the maximum yield (62- 64 Kg/ tree). With regard to fruit quality, the same treatment increased fruit weight, length, diameter, firmness, pulp/stone ratio, and total soluble solids content, but decreased titratable acidity in Santa Rosa plum. In addition, total carbohydrates, total nitrogen, and C/N ratio in leaves were higher in treated trees than the control ones. Anatomical studies indicated that inactive embryo development after ovule fertilization may be the major cause of young fruit drop observed in ‘Santa Rosa’ plum trees. Furthermore, there was a relationship between physiological fruit drop which occurred from the middle of Growth Stage 2 to the beginning of Growth Stage 3, and seed development which contains inactive endosperm. From this study, it can be concluded that the combination of AA, NAA, and NAD increased fruit set, reduced fruit abscission, enhanced C/N ratio in leaves, and improved fruit yield and quality of Santa Rosa plum. Thus, it may be recommended to spray AA 0.25 ml/l +NAA 10 ppm + NAD 10 ppm under similar conditions

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.

Sweet pepperincludes several vitamins and is regarded as a great source of bioactive nutrients, such as carotenoids and phenolic compounds, for human growth and activities. This work aimed to investigate the effects of the soil addition of growth stimulants, namely, effective microorganisms (EM), compost tea, fulvic acid, and yeast extract, and foliar applications of seaweed extract, on the vegetative growth, enzyme activity, phytohormones content, chemical constituents of plant foliage, fruit yield, and fruit quality of sweet pepper plants (Capsicum annuum L. cv. Zidenka) growing under greenhouse conditions. The results showed that the tallest plant, largest leaf area/plant, and heaviest plant fresh and dry weights were recorded after combining a soil addition of yeast extract and foliar spray with seaweed extracts at 3 g/L in two growing seasons. The highest number of fruit/plant, fruit yield/m2, fruit values of vitamin C (VC), total sugars, total soluble solids (TSS), and carotenoids, along with the highest leaf of cytokines, P, K, Fe, and total carbohydrates values, were obtained using a soil addition of fulvic acid and spray with seaweed extract at 3 g/L in the two seasons of study. These treatments also provided the lowest abscisic acid, peroxidase, and super oxidase dismutase values in the same conditions. Sweet pepper plants supplemented with compost tea and seaweed extract foliar spray at 3 g/L were the most promising for inducing the highest values of fruit fresh and dry weights, fruit length and diameter, and the leavesrichest in N, Zn, and Mn; inversely, it induced the lowest catalase levels in both seasons. The applications of EM, yeast extract, and seaweed extract could be applied for high growth, mineral levels, enzymatic activity, fruit yield, and nutritional value of sweet pepper fruit and minimizing environmental pollution.

Aim: The main aim of this study was to evaluate the impact of seaweed and humic acid treatment at different doses on the phenological characteristics and yield of guava. Study Design: Randomized block design. Place and Duration of Study: A field experiment was conducted from December 2023 to July 2024 to assess the impact of bio-stimulants on the phenological and yield traits of guava (var. Arka Kiran) in the Poongunam village, Chengalpattu Dist, Tamil Nadu, India. Methodology: The experiment followed a Randomized Block Design with eight treatments: T₁ - Absolute control, T₂ - Water Spray, T₃ - 1% Seaweed Extract, T₄ - 1.5% Seaweed Extract, T₅ - 2% Seaweed Extract, T₆ - 1% Humic Acid, T₇ - 1.5% Humic Acid, and T₈ - 2% Humic Acid, each replicated three times. Results: Results showed that 2% Seaweed Extract (T₅) significantly improved flower retention (7.55 flowers per shoot), reduced the duration from flowering to fruit set (12.47 days), and shortened the time from fruit set to harvest (121.56 days). T₅ also led to the highest fruit set (68.65%), lowest fruit drop (48.72%), largest fruit weight (150.02 g), and greatest yield (13.35 kg/tree). Humic Acid at 2% (T₈) also improved fruit set (64.32%), fruit drop (49.54%), and yield (12.34 kg/tree), but was less effective than Seaweed Extract. Conclusion: This study demonstrates the potential of Seaweed Extract as a powerful bio-stimulant to enhance guava production, offering a sustainable alternative to traditional chemical treatments.

• Poor fruit set and excessive fruit drop are key challenges in the global mango industry. • Inadequate pollination, fertilisation and unfavourable climatic conditions lead to poor fruit set. • Mango fruit drop is mainly controlled by PGRs and environmental factors. • This review provides critical insights for improving fruit set and retention in mango. Insufficient fruit set and excessive fruit drop are key challenges faced within the global mango ( Mangifera indica L.) industry, affecting yield consistency and grower’s income as well as adversely impacting global mango trade. Rising temperature regimes and extreme weather events at critical stages of fruit set and development are among the primary driving factors behind these extremely devastating issues in the mango industry. Scientific interventions aimed at regulating fruit set and drop have become increasingly important. Inadequate pollination and fertilisation can also cause poor fruit set, whilst self-incompatibility and stenospermocarpy can cause fruit drop in mango. Mango fruit set and drop are mainly controlled by plant hormones such as auxins, cytokinins, gibberellins, polyamines, and ethylene, all of which are influenced by changes in the environment and other biotic or internal signals. This review focuses on the impact of plant growth regulators and nutrients, such as auxins, gibberellins, cytokinins, brassinosteroids, tryptophan, boron, sucrose, putrescine, aminoethoxyvinylglycine (AVG), cobalt sulphate (CoSO₄) and emerging genetic and omics approaches on mango fruit set and fruit drop. The impacts of major environmental conditions and agronomic practices affecting fruit set and drop were also analysed. This review provides critical insights for improving mango fruit set and retention in the current era of climate change. Despite numerous worldwide studies on these factors individually, a comprehensive compilation of their positive influences and limitations on fruit set and drop is lacking. This review bridges this gap by synthesising current research, clarifying the benefits and drawbacks of existing methods to modulate mango fruit set and retention, and proposing potential solutions to address these challenges in the global mango industry.

Leaf damage/defoliation caused by pests or phytotoxic damage following chemical application can result in loss of leaf area at any time during the growing season. Four trials were conducted to examine the impact of severity and time of foliar damage on fruit set and quality in apple. Trees tolerated light to moderate leaf damage throughout the season with no significant effect on fruit set and thus crop load. Where 75% or more of the leaf surface was lost, fruit set was reduced and fruit quality was affected. Complete loss of leaves up to three weeks after full bloom (wAFB) resulted in very low or no fruit set, but from 9 wAFB crop load was not affected by leaf damage. Loss of terminal shoot leaves had no effect on fruit set, but spur leaves were critical early in the season with the impact lessening from 6 wAFB. This study has demonstrated that low levels of foliar damage have little effect on fruit size or quality, but high levels can impact on both set and quality. Fruit quality was reduced following leaf damage during the period 6–12 weeks after full bloom which is the critical period for cell division in the fruit as well as flower initiation for the following year. High levels of leaf damage also reduced fruit size in spite of reduced crop load levels, most likely the result of a reduction in carbohydrate assimilation during the cell division phase of fruit development.

Effects of hydrogen cyanamide and Wilthin on blossom thinning and the consequences of thinning on fruit set, yield and fruit quality of `Rome Beauty' was studied. A full bloom application of hydrogen cyanamide at the rate of 0.25% (Dormex formulation) or 0.25% of Wilthin both followed by a fruit thinning by Sevin + NAA effectively thinned mature trees of `Rome Beauty' and had a similar effect on fruit set, yield and fruit quality. The effects of these two chemicals at these rates on several aspects of fruit set, yield and quality were similar to the effects of Elgetol. Hydrogen cyanamide, Elgetol and 0.25% Wilthin at full bloom resulted in a higher percentage of single fruit set, thus, less labor for hand thinning. Application of 0.37% Wilthin at 20% bloom or at full bloom resulted in larger fruit size, but induced fruit russetting. Soluble solids of fruit from trees with Elgetol, 0.37% Wilthin at 20% bloom or at full bloom were higher than fruit from other treatments. Hydrogen cyanamide at 0.50% resulted in a satisfactory level of blossom thinning in `Friar' plums.

Although the application of chemical fertilizers to crops promotes plant growth and yield, their continuous use affects soil heath and creates environmental pollution. On the other hand, plant biostimulants improve nutrients absorption, plant growth, yield and produce quality and are environment-friendly. Therefore, an experiment was conducted during 2021-22 to evaluate the effect of some biostimulants on the performance of the apple cv. Anna, planted in a sandy loam soil at Marsa Matruh governorate, Egypt. Ninety trees were randomly selected and sprayed with 4 or 6% moringa leaf extract (MLE), 0.3 or 0.4% seaweed extract (SWE), 1000 or 2000 mg L−1 Fulvic acid (FA), 4% MLE + 0.3% SWE + 1000 mg L−1 FA (combination 1), or 6% MLE + 0.4% SWE + 2000 mg L−1 FA (combination 2) before flowering, during full bloom and one month later and compared with a control (untreated trees). The results demonstrated that spraying MLE, SWE or FA or their combinations positively improved the vegetative growth, fruit set %, fruit yield and fruit physical and chemical characteristics as well as leaf nutritional status. The positive effect of MLE, SWE and FA was increased in parallel to an increase in the used concentration of each one of them. The highest increments in the measured parameters were accompanied by the application of combination 2 over the other treatments.