Brown Rot Incidence Research Articles

A metapopulation framework integrating landscape heterogeneity to model an airborne plant pathogen: The case of brown rot of peach in France

Plant disease dynamics are driven by the concurrent interplay of host susceptibility, pathogen presence, and environmental conditions. While host susceptibility and environmental conditions can readily be characterized, the transmission of an airborne pathogen depends on the biotic and abiotic conditions of the surrounding environment. We propose an original metapopulation framework integrating landscape heterogeneity, in terms of climate and host density, where populations of plant hosts are connected via air-masses which allow pathogen dispersal. We explicitly account for climatic drivers affecting pathogen transport while modelling aerial dispersal using Lagrangian simulations, as well as host phenology and infection. We calibrate the model parameters according to the literature and using Approximate Bayesian Computation against observations of brown rot incidence in French peach orchards from 2001 to 2020 across an area of 50,000 km2. We use the model to produce maps of risk, distinguishing site dangerousness (risk of causing secondary infection in other sites) and vulnerability (risk of becoming infected) across the our study area. We demonstrate that airborne transport of Monilinia spores is essential in describing the spread of brown rot in French orchards in the considered period. We find that most dangerous and vulnerable sites are located along the Rhône Valley, due to the concurrence of high density of peach cultivation, a suitable climate and persistent airborne connections. Our work represents a first step to integrate metapopulation theory, epidemiology and air-mass movements to inform plant protection strategies at the national level. Furthermore, it could be adapted to optimize crop protection under future climate projections.

Combined application of alginate oligosaccharide and marine yeast Sporidiobolus pararoseus to control brown rot of peach fruit

Brown rot caused by Monilinia fructicola is the major fungal disease during postharvest storage of peach fruit. In this study, the effects of marine yeast Sporidiobolus pararoseus and alginate oligosaccharide (AOS) used alone or in combination to control brown rot in peach fruit were investigated. The results showed that AOS and S. pararoseus used alone could reduce the disease incidence and lesion diameter of brown rot, and their combination significantly increased the control effect than either treatment alone. Especially in the early stage of disease, the incidence of the untreated control fruit has reached 90%, while the incidences of AOS and S. pararoseus treatment were 36.7% and 30%, however, the combination treatment only showed 13.3% of incidence. The combination treatment of AOS and S. pararoseus can also reduce the weight loss and maintain fruit quality of peaches. Meanwhile, AOS could promote the colonization of S. pararoseus in peach fruit wounds and improve the survival of S. pararoseus under stresses. The combined treatment of S. pararoseus and AOS significantly increased the activities and gene expression of resistance-related enzymes such as catalase (CAT), phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), β-1,3-glucanase (GNS), chitinase (CHI), promoted the accumulation of total phenols. These findings indicated that the increased biocontrol efficacy of AOS combined with S. pararoseus may be attributed to the promoting growth of S. pararoseus by AOS and the enhanced disease resistance of peaches. Overall, the combined application of AOS and S. pararoseus could be an effective method to control brown rot of peach fruit.

Genome-wide association analysis of Monilinia fructicola lesion in a collection of Spanish peach landraces

Brown rot, caused by the Monilinia spp., is the disease that causes the greatest losses in stone fruit worldwide. Currently, M. fructicola has become the dominant species in the main peach production area in Spain. The fruit cuticle is the first barrier of protection against external aggressions and may have a key role in the susceptibility to brown rot. However, information on the role of skin fruit on the resistance to brown rot in peach is scarce. Previous genetic analyses in peach have demonstrated that brown rot resistance is a complex and quantitative trait in which different fruit parts and resistance mechanisms are involved. To search for genomic areas involved in the control of the cultivar susceptibility to brown rot and to elucidate the role of fruit skin against this infection, we have studied, for two consecutive seasons (2019 and 2020), the fruit susceptibility to M. fructicola, together with fruit cuticle thickness (CT) and density (CD), in a collection of 80 Spanish and 5 foreign peach cultivars from the National Peach Collection at CITA (Zaragoza, Spain). Brown rot incidence, lesion diameter, and severity index were calculated after 5 days of inoculation on non-wounded fruit. The peach collection has also been genotyped using the new peach SNP chip (9 + 9K). Genotypic and phenotypic data have been used to perform a genome-wide association analysis (GWAS). Phenotyping has shown a wide variability on the brown rot susceptibility within the Spanish germplasm as well as on CD and CT. The GWAS results have identified several significant SNPs associated with disease severity index (DSI), CD, and CT, five of which were considered as reliable SNP-trait associations. A wide protein network analysis, using 127 genes within the regions of the reliable SNPs and previously identified candidate genes (169) associated with Monilinia spp. resistance, highlighted several genes involved in classical hypersensitive response (HR), genes related to wax layers as ceramidases and lignin precursors catalyzers, and a possible role of autophagy during brown rot infection. This work adds relevant information on the complexity resistance mechanisms to brown rot infection in peach fruits and the genetics behind them.

Low frequency of resistance to thiophanate-methyl in Monilinia fructicola populations from southeastern United States peach orchards

Methyl benzimidazole carbamate (MBC) fungicides were once widely used for brown rot (Monilinia fructicola) control of peach (Prunus persica (L.) Batsch) in the southeastern US, but their use was substantially reduced and often eliminated due to widespread resistance. In this study, 233 M. fructicola isolates were collected from major peach production areas in Alabama, Georgia, and South Carolina, and sensitivity to thiophanate-methyl was examined. Isolates were also collected from one organic and two experimental peach orchards. A discriminatory dose of 1 μg/ml was used to distinguish sensitive (S) and moderately sensitive (S-LR) isolates from low resistant phenotypes, while 50 and 500 μg/ml thiophanate-methyl concentrations were used to determine high resistant (HR) phenotypes. Sequence analyses were performed to identify mutations in the β-tubulin target gene and detached fruit assays were performed to determine the efficacy of a commercial product against isolates representing each phenotype. Results indicated 55.7%, 63.5%, and 75.9% of isolates from Alabama, Georgia, and South Carolina, respectively, were S to thiophanate-methyl; 44.3%, 36.5%, and 21.4% were S-LR; no isolates were LR; and only 3 isolates (1.3%) from South Carolina were HR. No mutations in S or S-LR isolates were found, but HR isolates revealed the E198A mutation, an amino acid change of glutamic acid to alanine conferring high resistance. The high label rate of a commercial product containing thiophanate-methyl controlled brown rot caused by S and S-LR isolates in detached fruit studies but was ineffective against HR isolates. The combinations of thiophanate-methyl with azoxystrobin or isofetamid, when mixed together and applied in an experimental orchard 14 days preharvest, significantly reduced brown rot incidence on pre and postharvest commercially ripe fruit and efficacy was comparable to that of a grower standard fungicide. These results indicate that thiophanate-methyl may again be useful to peach growers in the southeastern US for brown rot and fungicide resistance management.

Hydroxypropyl Methylcellulose and Gum Arabic Composite Edible Coatings Amended with Geraniol to Control Postharvest Brown Rot and Maintain Quality of Cold-Stored Plums.

In this study, the effect of hydroxypropyl methylcellulose (HPMC) and gum Arabic (GA) edible coatings amended with 0.2% geraniol (GE) were evaluated for the control of brown rot, caused by Monilinia fructicola, on artificially inoculated plums (Prunus salicina Lindl., cv. Angeleno) stored for 5 weeks at 1 °C. Brown rot is the most important pre- and postharvest fungal disease of stone fruits, causing severe economic losses worldwide. Geraniol is an important constituent of many essential oils that can be obtained as a byproduct from different industrial procedures, such as those of the juice industry. Fruit postharvest quality was also evaluated after 5 and 8 weeks of storage at 1 °C, followed by 3 days at 7 °C plus 5 days at 20 °C, simulating packinghouse, transport, and retail shelf-life conditions, respectively. HPMC coatings containing 0.2% GE reduced the incidence and severity of brown rot by 37.5 and 64.8%, respectively, compared to uncoated fruit after 5 weeks of storage at 1 °C. HPMC-coated plums, with and without GE, showed the highest level of firmness, the lowest change in external peel color parameters (L*, a*, b*, C*, hue), and the lowest flesh bleeding compared to uncoated control and GA-coated samples throughout the entire storage period, which correlated with a higher gas barrier of these coatings without negatively affecting sensory quality. Furthermore, the HPMC-0.2% GE coating provided the highest gloss to coated plums, showing the potential of this coating as a safe and environmentally friendly alternative to conventional fungicides and waxes for brown rot control and quality maintenance of cold-stored plums.

New Preharvest Treatments and Strategies in Managing Phytophthora Brown Rot of Citrus in California.

Brown rot caused by Phytophthora citrophthora, P. nicotianae, P. syringae, and P. hibernalis is an important fruit disease of citrus in California, and the latter two species are quarantine pathogens in some important export markets. The newly registered fungicides oxathiapiprolin (OXA) and mandipropamid (MAN), as well as a premixture of the two (MAN+OXA) were compared to standard fixed copper and potassium phosphite (KPO3) treatments under field conditions in two citrus production regions of California. Fruit were sampled periodically over 8 weeks after application in winter or spring seasons, inoculated with zoospores of P. citrophthora or P. syringae, and brown rot incidence was evaluated. Single applications with all fungicides significantly reduced brown rot incidence of fruit harvested after 8 weeks as compared with the control in seasons with different amounts of precipitation (i.e., 17.2 to 153.9 mm between application and the 8-week sampling). MAN and OXA were similarly or significantly more effective than copper or KPO3. Two applications done in November and January significantly improved the efficacy of KPO3 and copper when compared to a single application of each fungicide done in January. For MAN and OXA, however, a single application was similar in efficacy as two applications. Two-application rotations of MAN, OXA, MAN+OXA, or copper significantly reduced the disease incidence by >84% from the control for at least 8 weeks after the second application. Low-volume (935 liters/ha) applications of MAN, OXA, MAN+OXA, or KPO3, but not copper, were significantly more effective than industry standard high-volume (3,740 liters/ha) applications. Thus, our studies identified and supported registration of new preharvest fungicide treatments to manage brown rot of citrus that are highly effective and persistent, and we optimized treatment strategies. Additionally, rotational programs with fungicides with different modes of action will minimize resistance development in pathogen populations and extend the usage of these fungicides.

Effect of peach trichome removal on post-harvest brown rot and on the fruit surface microbiome

Postharvest peaches undergo rapid soft ripening and are susceptible to fungal diseases, which often result in severe losses during storage. The peach epidermis contains trichomes that form a specific structure on the peach surface. However, the relationship between trichomes and postharvest disease and involved mechanisms has not been well studied. In this study, the removal of trichomes reduced the disease incidence of peach brown rot caused by Monilinia fructicola. Cryo-scanning electron microscope observations showed that the fungal hyphae were found attached to the surface of trichomes. The fungal and bacterial communities on the peach surface at 0 d and 6 d were obtained by amplicon sequencing technology. Fungal communities on the peach surface contained a total of 1089 amplicon sequence variants (ASVs), which were demarcated into eight fungal phyla, 25 classes, 66 orders, 137 families, and 228 genera. The bacterial communities contained 10,821 ASVs assigned to 25 phyla, 50 classes, 114 orders, 220 families, and 507 genera. Higher bacterial diversity than fungal diversity was recorded on the peach epidermis. Trichome removal changed the microbial diversity and community on the peach surface. Compared with peach epidermis samples, the peach epidermis excluded trichomes samples contained similar fungal alpha diversity but significantly lower bacterial diversity. Seventeen different fungal genera and twenty-eight different bacterial genera were identified between peach trichome and peach epidermis excluded trichomes samples. The fungal and bacterial diversity on the peach epidermis showed a decreasing trend during storage. Beta diversity analysis revealed that the microbial communities of the peach epidermis and trichomes show different change trends between 0 d and 6 d. Trichome removal decreased relative abundance of Monilinia spp. and increased relative abundance of potential yeast and bacterial biocontrol agents. This study suggested that trichomes might modulate the microbial communities on fruit surfaces, and trichome removal technology after harvest might be developed to control peach postharvest decay.

Physicochemical properties of peach fruit assessed by non-destructive methodology related to the development of Monilinia fructicola during postharvest

ABSTRACT The concomitant evaluation of physicochemical properties and development of important diseases, such as brown rot in peaches postharvest, is hampered by the use of destructive methods for physicochemical analysis. Therefore, this study aimed to evaluate the physicochemical characteristics in wounded and unwounded ‘Chimarrita’ and ‘Maciel’ peaches inoculated with M. fructicola assessed by non-destructive methods. The fruits were stored at room temperature (25 ºC) for 10 days after harvest. Colorimeter, near-infrared spectroscopy and portable spectrophotometer DA-meter® (single index of absorbance difference, IAD index) were used to evaluate the physicochemical changes that naturally occurred in peaches during postharvest and due to pathogen development on the same fruit simultaneously. Incidence and severity of brown rot were evaluated by counting the number of lesions resulting from inoculation at 24, 48 and 60 h post inoculation. Also, the sporulation of M. fructicola on fruit surface was evaluated. The results indicated that differences between wounded and unwounded fruits related soluble solids content, pulp firmness, titratable acidity, dry matter and IAD did not affect the incidence of M. fructicola in both cultivars. However, the interaction between dry matter and colour at the time of inoculation influenced colonisation and consequent lesion size in inoculated wounded ‘Chimarrita’ fruits.

Molecular characterization of Aureobasidium spp. strains isolated during the cold season. A preliminary efficacy evaluation as novel potential biocontrol agents against postharvest pathogens

Several Aureobasidium spp. strains isolated from wild environments during winter 2022 were characterized by sequence analysis of the internal transcribed spacer (ITS), the translation elongation factor EF-1α gene (EF1), and part of the elongase gene (ELO). The variability in the EF1 and ELO loci are higher than in the ITS. All strains but one (UC14), were identified as A. pullulans. To assess the effectiveness of the characterized strains as biocontrol agents (BCAs) of diseases occurring during postharvest storage, a selection of the strains was evaluated by in vitro and in vivo assays. On average, the reduction of Monilinia spp. colony growth was more marked for non-volatile metabolites than for volatile (VOCs). Strain UC14 provided the strongest mycelial growth reduction of Monilinia fructicola by VOCs (66%). According to the in vivo results, all strains were effective in controlling brown rot during cold storage and remarkably in restricting the growth of Monilinia polystroma. In particular, VB23 was the most effective in controlling brown rot incidence, by 80%, 60%, 100%, and severity, by 79.5%, 72.7% and 100%, for Monilinia laxa, M. fructicola, and M. polystroma, respectively.

Antifungal activities of aqueous extracts of moroccan medicinal plants against Monilinia spp. agent of brown rot disease

Apple fruit is one of the worldwide most industrially valuable horticulture crops. However, the fruit is vulnerable to post-harvest brown rot degradation caused by Monilinia laxa and Monilinia fructigena, which is a prominent pre-and post-harvest disease of tree fruit. Numerous non-chemical post-harvest treatments have been investigated so far to control these pathogens to provide an alternative option to the synthetic fungicides that are commonly used and may have negative effects on human health and the environment. Therefore, this study aimed to assess the in vitro and in vivo efficacy at different concentrations of nine plants' aqueous extracts from Mentha pulegium, Citrus aurantium, Thymus vulgaris, Origanum compactum, Lavandula angustifolia, Syzygium aromaticum, Rosmarinus officinalis, Citrus sinensis and Eucalyptus radiate against the development of brown rot. The results demonstrated significant antifungal activities of all tested aqueous extracts on both fungi compared to the thiophanate-methyl fungicide (1 ppm) (100% inhibition). At the concentration of 1.5 mg/ml, S. aromaticum and O. compactum extracts were the most effective, showing significant inhibition values against M. laxa (91.06%) and against M. fructigena (90.02%). Interestingly, at higher concentration, spore germination of both Monilinia strains was significantly reduced with inhibition rate of 98.64% for M. laxa and 93.04% for M. fructigena. Also, high flavonoids and polyphenols contents were shown. Aqueous extracts of O. compactum, S. aromaticum, and T. vulgaris reduced the brown rot severity and incidence in vivo. The application of these plants' aqueous extracts on fruits seems to have a significant effect on fruit quality persistence, as indicated by weight loss, fruit firmness, total soluble solids, titrable acidity, and maturity index during 15 days of storage at 4 °C. The spectra analyzed from all tested plants revealed typical peaks and a large variety of functional groups such as C–H bonds, O–H groups, and C–C stretching. The plant’s aqueous extracts studied can be used as bio-fungicides against brown rot diseases.

Identification of ‘Calanda’-Type Peach Genotypes Tolerant to Monilinia laxa (Aderh. & Ruhland) Honey

One of the diseases that has the greatest negative effect on peach production is brown rot, produced by the fungus, Monilinia spp. The way to diminish this disease is the selection of genotypes with a high tolerance to Monilinia spp. while maintaining fruit quality. In this study, the tolerance to Monilinia laxa and agronomic and biochemical characteristics of forty-two hybrids derived from the ‘Andross’ × ‘Calante’ cross were studied under controlled conditions during two consecutive years, and compared with their parents. The assessment of tolerance to brown rot was estimated on inoculated fruit with M. laxa, recording the incidence of brown rot and colonization, lesion diameter and extent of colonization, to establish the severity of incidence and colonization. At harvest, physicochemical traits and antioxidant compounds (vitamin C, total phenolics, flavonoids and relative antioxidant capacity) were determined. We have found inverse relationships between fruit firmness, pH, titratable acidity and antioxidant contents with the disease symptoms in fruit. Our results confirm that the accumulation of antioxidants tends to reduce the lesion and colonization in inoculated fruit. Principal component analysis allowed the selection of two genotypes, AC-24 and AC-93, of ‘Calanda’-type peaches with a known standard quality, high antioxidant content and minimal susceptibility to brown rot.

Influence of Biocontrol and Integrated Strategies and Treatment Timing on Plum Brown Rot Incidence and Fungicide Residues in Fruits

Brown rot caused by Monilinia spp. is the main disease of stone fruits. Our research aimed to identify an appropriate strategy to control plum brown rot and reduce fungicides residues in fruit through targeted application of the biocontrol agents (BCAs) Papiliotrema terrestris and Bacillus subtilis, alone or in combination with synthetic fungicides. The following treatments were evaluated: Biological (BIO1, BIO2), Integrated (INT1, INT2, INT3), and Combined (COMB), all compared with Chemical strategy. Five key treatments (seven for BIO2) were performed in the crucial phenological stages for the disease cycle: INT1, INT2, and INT3 approaches consisted, from the beginning of the season, of one, two, or three treatments, respectively, alternately with boscalid or cyprodinil followed by applications of BCA until the fruit harvest. After harvest, plums were subjected to an additional treatment with the two BCAs and the fruits were stored at 20 °C for 15 days. The results obtained by applying our BCA PT22AV, revealed, in the field and in postharvest, the highest level of disease protection with management strategies BIO2 (94.8–97.2% in field; 65–84% in postharvest) and INT3 (95.5–97% in field and 63% to 91% in postharvest). The level of fungicide residues in fruit was zero in BIO strategies and lower in INT strategies as compared to chemical strategy.

Breeding Peaches for Brown Rot Resistance in Embrapa

Brown rot, caused by Monilinia spp., is the main stone fruit disease. Major efforts to detect sources of resistance are being applied by several breeding programs worldwide. The main objective of this study was to seek sources of brown rot resistance, as well as to study the segregation, estimate the heritability, verify the possible existence of the maternal effect, and estimate the genetic advances. For this purpose, 20 parents and 303 seedlings, representing 16 breeding families, and ‘Bolinha’ (control) have been phenotyped for fruit reaction to brown rot using wounded and non-wounded inoculation procedures in 2015–2016, 2016–2017, and 2017–2018 growing seasons. Wounded fruits were very susceptible to brown rot incidence, however, the incidence and severity of non-wounded fruits showed high variability among the evaluated genotypes. Conserva 947 and Conserva 1600 and their progeny, had lower disease incidence and severity than most of the evaluated genotypes. Genetic gain estimation was −5.2 to −30.2% (wounded fruits) and between −15.0 to −25.0% (non-wounded fruits) for brown rot resistance. Selected genotypes were equal to or better than ‘Bolinha’ in relation to brown rot resistance, with several of them far superior in fruit quality than ‘Bolinha’, demonstrating the progress of the Embrapa Peach Breeding Program.

Brown Rot Disease in Stored Nectarines: Modeling the Combined Effects of Preharvest and Storage Conditions.

Brown rot in stored stone fruits, caused by Monilinia spp., may be due to preharvest and storage factors, but the combined effect of these factors has yet to be investigated. We set up two experiments to monitor the progression of brown rot during the storage of nectarines subjected to various preharvest and storage conditions. We assessed the effects of different agricultural practices (irrigation regimen × fruit load) and harvest dates on brown rot progress during storage in 2018 and the effect of different storage temperatures in 2019. We found that the cumulative incidence of brown rot during storage increased with individual fruit mass, which was influenced by agricultural practices, and for later harvest dates. It also increased with storage temperature. We observed that during storage no secondary infections developed in nectarines not in direct contact with fruits infected with Monilinia laxa. These findings led to the identification of candidate variables describing the brown rot risk on nectarines during storage, such as individual fruit mass, meteorological conditions before fruit harvest, prevalence of brown rot at harvest, and storage temperature. We used these variables to build a mathematical model for estimating the time-to-appearance of brown rot symptoms in stored nectarines. This model fitted the experimental data well, highlighting the need to pay greater attention to the interaction between preharvest and storage conditions. This model could be used to evaluate management strategies for reducing the impact of brown rot in nectarines during storage.

Development of brown rot epidemics in Spanish peach orchards

A new approach to modelling epidemics of brown rot caused by Monilinia spp. in Ebro Valley peach orchards has been developed. This compartmental model was subdivided according to the phenological stages in which the disease can develop (blossom, immature fruit, and ripe fruit). Information host susceptibility, primary and secondary inoculum sources and latent infections in immature fruit was taken into account. The compartmental model is described by a system of differential equations, and is simple enough to allow an analytical study of the main epidemiological factors that determine the rate of disease progress during a single growing season. The proposed model fits well to the epidemic pattern of brown rot observed in north-eastern Spain. The transmission of the disease as a non-linear term implied that small changes in the infection rate had a large effect on the development of the disease. The model has confirmed the usefulness of removing mummies (infected fruit that remains in the crop during winter) from the field to reduce the final incidence of the disease. In addition, all control measures that reduce the rate of secondary infection in ripe fruit, either through the use of more resistant varieties or the use of fungicides, are effective in reducing brown rot incidence. The proposed epidemic model is flexible and allows to add complexities to the system and evaluate the effectiveness of different control strategies.

High inoculum of Monilinia fructicola is a threat to peach production in the tropics due to fruit susceptibility at all development stages

AbstractBrown rot is the main disease of stone fruits in Brazil, but the susceptibility of peaches to brown rot at different stages of development in the field has not been studied under subtropical conditions. This information is relevant to guide the management of the disease. The objective of this research was to determine the influence of inoculating peaches with Monilinia fructicola at different stages of development on the infection and progress of brown rot at postharvest. Two experiments were carried out: one ex vivo with two cultivars and the other in the field for two seasons. Peaches were inoculated at different sizes for both experiments. In the field, peaches were bagged to avoid natural infection, and M. fructicola inoculum was monitored. The ex vivo incidence of the disease was lower at pit hardening than at other fruit stages for both cultivars. The incidence of brown rot for peaches attached to the trees increased with fruit ripening. Conversely, the time for symptom expression was reduced according to peach diameter. Peaches inoculated with a diameter smaller than 2 cm showed a lower incidence of brown rot and longer periods for disease expression than fruit inoculated near harvest. In conclusion, in areas with high inoculum in the orchard, a common condition in the subtropics, the grower must prevent infection at all stages of fruit development, thus avoiding losses during marketing.

Effect of foliar-applied silicon sources on brown rot (Moniliniafructicola)

The prevention of brown rot symptoms caused by Monilinia fructicola fungus in stone fruits is usually achieved by the repetitive use of chemical fungicides. However, foliar-applied silicon (Si) sources either alone or combined with fungicides, can be an effective alternative to reduce disease incidence, with beneficial cost and environmental impact. We carried out a set of experiments in field conditions with the aim of evaluating the effectiveness of foliar-applied Si sources, either in combination or not with fungicides, and applied at different phenological stages in preventing the brown rot occurrence in peach fruits. Three experiments were carried out in an 11-year-old Eldorado peach orchard, located in southern Brazil. Experiment 1 compared eight strategies in order to optimize the application timing. Experiment 2 was carried out to define the Si effect alone or combined with fungicides. Experiment 3 consisted of five treatments to verify the effect of different Si sources. The effects of the strategies in the pre and post-harvest brown rot incidence in fruits, fruit quality parameters and Si concentration in leaves and fruits were evaluated. Fruit anatomical investigation analysis was also performed. Si was effective in controlling brown rot in fruits. Six treatments with Si showed a similar effect compared to six fungicide applications. Si allowed a reduction of three fungicide applications, regardless of application period. Si foliar-treated trees revealed an increased leaf and fruit Si concentration. Si sources showed similar effectiveness in preventing the occurrence of brown rot incidence in fruits. Si represents a potential alternative in preventing brown rot incidence.

Biology, epidemiology, and management of diseases of peach driving the spray program in the southeastern United States

Due to weather conditions during the growing season that are often conducive for infection, peach crop disease management is an important aspect for the production of high-quality fruit in the southeastern United States. Fungicide and bactericide applications and resistance management strategies are important components of the integrated approach applied to manage fungal and bacterial diseases. A strategic approach to fungal disease and fungicide resistance management was developed and has been highly successful for southeastern U.S. growers – resulting in generally very little peach scab and preharvest or postharvest brown rot incidence over the past two decades. The chemical approach focuses on strategic use of multi-site and single-site fungicides with minimal risk of resistance development in the pathogens. However, management of bacterial spot remains challenging due to high disease pressure, lack of effective bactericides and effective non-chemical IPM tools, emergence of copper-tolerant strains, and lack of resistant cultivars that would meet consumer demand.

In Vitro and In Vivo Antifungal Activities of Nine Commercial Essential Oils against Brown Rot in Apples

After harvest, numerous plant pathogenic fungi can infect fresh fruits during transit and storage. Although synthetic fungicides are often used to manage postharvest fruit diseases, their application may lead to problems such as the development of fungicide resistance and residues on fruits. In the present study, the antifungal potential of nine commercial essential oils (EOs) extracted from Eucalyptus radiata ssp. radiata, Mentha pulegium, Rosmarinus officinalis, Origanum compactum, Lavandula angustifolia, Syzygium aromaticum, Thymus vulgaris, Citrus aurantium, and Citrus sinensis were tested against the apple brown rot fungi Monilinia laxa and Monilinia fructigena at different concentrations in vitro (against mycelial growth and spore germination) and in vivo (on detached apple fruit and in semi-commercial postharvest conditions). In addition, fruit quality parameters were evaluated and the composition of the EOs was characterized by Fourier transform infrared (FT-IR) spectroscopy. In vitro results showed significant antifungal activity of all tested EOs on both fungal species. EOs from S. aromaticum were the most effective, whereby inhibition percentages ranged from 64.0 to 94.7% against M. laxa and from 63.9 to 94.4% against M. fructigena for the concentrations 12.5 and 100 µL/mL, respectively, with an EC50 of 6.74 µL/mL for M. laxa and 10.1 µL/mL for M. fructigena. The higher concentrations tested of S. aromaticum, T. vulgaris, C. aurantium, and C. sinensis EOs significantly reduced spore germination, brown rot incidence, and lesion diameter. Evaluation of the treatments during storage for 20 days at 4 °C on apple fruit quality parameters demonstrated the preservation of the fruit quality characteristics studied (weight loss, total soluble solids, titratable acidity, firmness, and maturity index). FT-IR spectra obtained from all tested EO samples presented characteristic peaks and a high diversity of functional groups such as O–H groups, C–H bonds, and C–C stretching. The EOs examined here may have the potential for controlling postharvest fungal diseases of fruit such as brown rot.

Postharvest Treatments with Sulfur-Containing Food Additives to Control Major Fungal Pathogens of Stone Fruits.

The sulfur-containing salts, classified as food additives, sodium metabisulfite (SMBS), potassium metabisulfite (PMBS), aluminum sulfate (AlS), and aluminum potassium sulfate (AlPS), were evaluated for their activity against Monilinia fructicola, Rhizopus stolonifer, and Geotrichum candidum, the most economically important fungal pathogens causing postharvest disease of stone fruit. In in vitro tests with potato dextrose agar (PDA) Petri dishes amended with different concentrations of the salts (0, 10, 20, 30, 50, and 100 mM), SMBS and PMBS at all concentrations, AlS above 20 mM, and AlPS above 30 mM, completely inhibited the mycelial growth of the three fungi after incubation at 25 °C for up to 10 days. In in vivo primary screenings with artificially inoculated nectarines, aqueous solutions of the four salts reduced the incidence and severity of brown rot (BR) at concentrations of 10 and 50 mM, whereas only AlS and AlPS reduced Rhizopus rot (RR), and none of the salts was effective against sour rot (SR). Solutions at 100 mM were phytotoxic and injured the fruit peel. In small-scale trials, 1 min dip treatments at 20 °C in SMBS or PMBS at 10 mM significantly reduced the incidence and severity of BR after incubation at 20 °C for up to 8 days. Conversely, dips in AlS and AlPS reduced neither BR nor RR. Results highlight the potential of SMBS and PMBS as new nonpolluting tools for the integrated control of BR, but not RR and SR, on stone fruit.