Biological Control of Blossom Blight and Brown Rot Caused by Monilinia laxa by Using a Bacillus subtilis Strain TV-6F

Integrated control of brown rot of sweet cherry fruit with a preharvest fungicide, a postharvest yeast, modified atmosphere packaging, and cold storage temperature

Control of Monilinia spp. on stone fruit by curing treatments : Part I. The effect of temperature, exposure time and relative humidity on curing efficacy

Gray mold and brown rot, caused respectively by Botrytis cinerea and Monilinia spp., are fungal diseases responsible for significant losses during the storage of fruit and vegetables. Nowadays, the control of postharvest diseases is shifting towards more sustainable strategies, including the use of plant secondary metabolites. In this study, the antifungal activity of Origanum vulgare, Thymus vulgaris, Thymus serpyllum, Melaleuca alternifolia, Lavandula officinalis, Lavandula hybrida, Citrus bergamia, Rosmarinus officinalis, Cinnamomum zeylanicum essential oils (EOs) in vapor phase was tested in vitro against B. cinerea, Monilinia fructicola, Monilinia fructigena, and Monilinia laxa. For the experiments, a protocol using a volatile organic compounds (VOC) chamber was designed. Results indicate a dose-dependent inhibitory activity of all the tested EOs, with O. vulgare, T. vulgaris, and T. serpyllum being the most active ones, with minimum inhibitory concentrations (MIC) of 22.73, 45.45, and 22.73 µl/L, respectively, against B. cinerea and a range between 5.64 and 22.73 µl/L against the three Monilinia spp. Overall, B. cinerea presented lower sensitivity to vapor-phase EOs than any of the Monilinia strains, except for the C. zeylanicum EO, which consistently showed higher inhibition against B. cinerea. Among the three Monilinia spp., M. fructicola was the least sensitive, while M. fructigena was the most sensitive. The use of VOC chambers proved to be a reliable protocol for the assessment of antimicrobial activities of EOs. These results suggest that the VOC emitted by the tested EOs are effective towards important decay-causing fungi, and that they could be used for the control of gray mold and brown rot in in vivo trials.

Ethanol at concentrations ≥30% improved the efficacy of benomyl-DCNA mixtures in 1-min dip treatments for control of postharvest brown rot in peach. The model of the regression analyses was significant (P≤0.01) and linear first=0.97). The slope of the equation for the incidence of brown rot and the concentration of ethanol with fungicide was similar, but the Y intercept and midpoint values were lower than when ethanol was used alone. Control of brown rot was best with 70% ethanol, but shriveling of fruit epidermis from dehydration was greatest at this concentration (...)

The efficacy of the antagonistic yeasts Pseudozyma fusiformata AP6, Metschnikowia fructicola AP47 and Aureobasidium pullulans PL5 were investigated, in combination with hot water dipping (HWD), to control brown rot of peaches caused by Monilinia laxa. The effects on postharvest fruit quality were also evaluated under semi-commercial conditions. In potato dextrose broth, HWD at 50°C for more than 40 s or at 55-60°C for more than 10 s completely suppressed M. laxa spore germination and germ tube elongation. In fruits inoculated by wounding, HWD at 55°C for 50 s significantly reduced brown rot decay and maintained fruit quality. This treatment would be optimal for commercial application. The harvested fruits were dipped in HW at 55°C for 50 s, cooled to 1°C for 10 min, dipped in the selected yeast cell suspension (108 cells ml−1) for 60 s, and then stored at 1°C and 95% relative humidity (RH). After 21 days, the disease incidence was measured and the postharvest quality parameters of the fruits, including firmness, total soluble solids, ascorbic acid and titratable acidity, were measured. When used alone, the antagonists AP6, AP47 and PL5 reduced brown rot incidence on the peaches to 28.3%, 30.0% and 25.8%, respectively, compared with 74.2% for the untreated control. However, when applied together with HWD, AP6, AP47 and PL5 reduced brown rot incidences to 16.7%, 15.8% and 17.5%, respectively, while when HWD was used alone, disease incidence was 30.0%, suggesting that HWD greatly increased the effectiveness of the antagonists. In combination with HWD, the efficacies of AP6, AP47 and PL5 signifi-cantly increased from 61.8%, 59.6% and 65.2% to 77.5%, 78.7% and 76.4%, respectively, and they were similar to the efficacy of tebuconazole (77.5%). Analysis of postharvest quality indicated that none of the treatments damaged fruit quality. Our results showed that the three antagonists combined with HWD at 55°C for 50 s exhibited potential for commercial use, as an effective alternative to fungicides in controlling postharvest brown rot of peaches. This appears to be the first report on combined application of yeast strains M. fructicola or P. fusiformata with HWD to control M. laxa on peaches.

The effects of wounding, inoculum density, and three isolates (New, Ta291, and 23-E-6) of Trichoderma spp. and one isolate (BI-54) of Rhodotorula sp. on postharvest brown rot of stone fruits were determined at 20°C and 95% relative humidity (RH). Brown rot was observed frequently on wounded nectarine, peach, and plum fruits inoculated with two spores of Monilinia fructicola per wound, and occasionally on unwounded nectarine and peach fruits inoculated with the same spore load. Brown rot was observed on wounded plums only. A substantial increase in lesion diameter of brown rot was also recorded on wounded nectarines and peaches inoculated with suspensions of ≤20 spores and ≤200 spores per wound, respectively, compared with unwounded fruit. At concentrations of 107 and 108 spores per ml, all Trichoderma isolates substantially reduced brown rot on peaches (63 to 98%) and plums (67 to 100%) when fruits were inoculated with M. fructicola following the application of a biological control agent. Similarly, at 108 spores per ml, the yeast BI-54 also suppressed brown rot on peaches completely and on plums by 54%. Significant brown rot reduction was also achieved with the isolate New at a concentration of 108 spores per ml, even when the biocontrol agent was applied 12 h after inoculation with M. fructicola and under continuous conditions of 95% RH. The isolates Ta291 and 23-E-6 also reduced brown rot significantly under drier (50% RH) incubation conditions. These isolates provided the best control of brown rot on plums when they were applied 12 h earlier than inoculation with M. fructicola. Satisfactory control of brown rot on plums inoculated with M. fructicola at 8 × 104 spores per ml was achieved with New at 106 spores per ml and with Ta291 at 107 spores per ml. Measures taken to avoid injuring fruit will greatly reduce brown rot of stone fruit at any spore load for plum, but only at ≤50 spores per mm2 for peach, and at ≤5 spores per mm2 for nectarine. This study identifies two isolates (Ta291 and New) of Trichoderma atroviride, one isolate (23-E-6) of T. viride, and one of Rhodotorula sp. that show potential for further development as biocontrol agents of postharvest brown rot of stone fruits.

Selection and evaluation of new antagonists for their efficacy against postharvest brown rot of peaches

The brown rot, caused by the fungus Monilinia fructicola , is the main cause for losses in pre and postharvest of peaches. The study aimed to evaluate the efficiency of preharvest application of fungicides on the control of brown rot in the field and during cold storage, and its relation to parameters of maturation and fruit quality. Therefore, we evaluated the following active ingredients: [1] control (water application), [2] captan; [3] iprodione; [4] iminoctadine; [5] tebuconazole; [6] procymidone; [7 ] azoxystrobin; [8] difenoconazole; [9] azoxystrobin / difenoconazole; [10] trifloxystrobin / tebuconazole; [11] sequence iminoctadine + captan; [12] sequence iminoctadine + iprodione; [13] sequence of tebuconazole + captan; [14] sequence of tebuconazole + iprodione. All treatments were applied according recommended doses and grace period for culture. The fruits were evaluated at harvest and after 40 days storage at –0.5 ° C, plus six days at 20 o C. At harvest time, the best control of brown rot was obtained with difenoconazole, while the fungicide iminoctadine and its association with iprodione showed good results in controlling brown rot after 40 days of cold storage, plus six days shelf life at 20 o C. The preharvest application of captan cause skin browning. The fungicide azoxystrobin influences the fruit maturation by decreasing acidity and firmness at harvest. Good levels of control of brown rot of peach can be achieved with the use of iminoctadine and iprodione.

Control of Monilinia spp. on stone fruit by curing treatments. Part II: The effect of host and Monilinia spp. variables on curing efficacy

Peach cover spray applications of the protectant fungicide captan were previously shown to significantly reduce brown rot caused by Monilinia fructicola during the preharvest fruit ripening periods in the 2012 through 2015 growing seasons. The protectants sulfur, ziram, and thiram failed to yield this benefit. Percentage disease control with captan ranged from 50 to 69%. Results of a bioassay indicated that the mechanism for this control was the creation of an effective, persistent fungicide residue on the fruit surface. Given these findings, the current 2017 to 2018 study was initiated to further refine the cover spray program. Cover spray applications of captan were made at lower rates and fewer timings with the goal of minimizing fungicide usage while maintaining control. High concentrations of the protectants sulfur and ziram were also examined in cover spray programs to determine whether greater concentrations could improve control. Results of the captan treatments from both years showed that the concentration could be reduced 17%, from 3.36 to 2.80 kg/ha active ingredient, without a significant increase in rot at harvest. Disease control at this medium rate was 69% in 2017 and 51% in 2018. The late season timing treatment, which consisted of the final two cover sprays at fifth and sixth cover, significantly reduced brown rot at harvest and provided control equivalent to the full cover spray program consisting of seven applications. Thus, a buildup of residue from many cover sprays is not needed to achieve control. As hypothesized, the midseason treatments, which consisted of two sprays at third and fourth cover, did not provide control of brown rot at harvest. The bioassay confirmed that insufficient residue remained on fruit for adequate control. However, the early season treatment, which consisted of sprays at shuck split, first cover, and second cover, provided 40% control, even though the bioassay showed that an effective residue was not present during the preharvest period. Brown rot management for this treatment was probably caused by inhibition of quiescent or latent infections on young green fruit. If confirmed, this novel finding indicates that high levels of latent infections are possible in eastern U.S. peach growing regions. Finally, higher rates of sulfur and ziram cover sprays were still ineffective for providing brown rot control at harvest. Comparison of half maximal effective concentration values calculated from the dose-response models confirmed that the sulfur and ziram intrinsic efficacies were too low for adequate control, even at the highest registered rates. These findings demonstrated that late season captan cover sprays can contribute significantly to control of brown rot at harvest, thereby augmenting the efficacy of preharvest fungicide programs. The year-to-year consistency of control should also be improved because heavy rainfall during the preharvest period did not reduce control by the captan residue. Furthermore, any reduction of the M. fructicola population by the captan cover sprays should reduce selection pressure against the site-specific fungicides commonly used during the preharvest period. The development of resistance to captan, a multisite protectant fungicide, is not likely, so this resistance management strategy should be sustainable.

Pathogenic fungi cause skin darkening and peach quality depreciation in post harvest. Therefore, alternative techniques to chemical treatment are necessary in order to reduce risks to human health. The aim of this study was to evaluate the effect of the application of Trichoderma harzianum in association with different fungicides applied before harvest to 'Eldorado' peaches for brown rot control and other quality parameters during storage. The treatments consisted of five preharvest fungicide applications (control, captan, iprodione, iminoctadine and tebuconazole) associated with postharvest application of T. harzianum, after cold storage (with and without application), in three evaluation times (zero, two and four days at 20 °C), resulting in a 5x2x3 factorial design. The application of T. harzianum only brought benefits to the control of brown rot when combined with the fungicide captan, at zero day shelf life. After two days, there was a greater skin darkening in peaches treated with T. harzianum compared with peaches without the treatment, except for peaches treated with the fungicide iprodione and T. harzianum The application of T. harzianum during postharvest showed no benefits for the control of brown rot, however, the association with fungicides reduced the incidence of Rhizopus stolonifer during the shelf life.

Peach brown rot and blossom blight are caused by Monilinia fructicola in the southeastern United States. Management is primarily achieved with synthetic fungicides, and little is known about the potential for biologicals to serve as alternatives. Recent studies found that the biorational fungicide Howler EVO (Pseudomonas chlororaphis AFS009) + the demethylation inhibitor (DMI) fungicide propiconazole reduced lesion development synergistically under lab conditions. This study evaluated the field efficacy of Howler EVO and another biological fungicide, Theia (Bacillus subtilis AFS032321), in combination with Propi-Star EC (propiconazole) or Cevya (mefentrifluconazole) to control of blossom blight and brown rot in nectarines over multiple years at the Clemson University Musser Fruit Research Center, Seneca, SC. Results showed that Howler EVO + the half label rate of Propi-Star EC (1/2 Propi-Star EC) synergistically reduced blossom blight incidence. Postharvest brown rot incidence was also reduced by Howler EVO + 1/2 Propi-Star EC. Both Howler EVO + 1/2 Propi-Star EC and Howler EVO + the full rate of Propi-Star EC (Propi-Star EC) revealed synergistic interactions. Theia + the half label rate of Cevya (1/2 Cevya) was as effective as Cevya in postharvest evaluations, with synergism observed in one of the experimental years. A discriminatory dose assay confirmed that the M. fructicola population at the research station was largely sensitive to DMI fungicides. This study illustrates that biologicals have the potential to be integrated into management programs to reduce chemical input in commercial nectarines and peach orchards.

O objetivo desse trabalho foi avaliar o efeito in vitro e in vivo dos sanificantes cloreto de benzalcônio (Fegatex®), biomassa cítrica (Ecolife40®) e ozônio no controle da podridão parda (Monilinia fructicola) e da podridão mole (Rhizopus stolonifer) em pêssegos das cultivares Aurora, Dourado e Flor da Prince. Cloreto de benzalcônio e biomassa cítrica, aplicados in vitro, ambos na concentração de 1000 mL L-1, inibiram totalmente o crescimento radial (micelial) de M. fructicola, porém nenhum deles foi eficiente no controle de R. stolonifer. Cloreto de benzalcônio aplicado de forma preventiva, na concentração de 3000 mL L-1, reduziu a podridão parda em frutos inoculados sem ferimentos. Quando aplicado de forma curativa em frutos não feridos esse produto foi eficiente em todas as concentrações testadas. Nenhum produto aplicado nos frutos de forma curativa foi eficiente no controle da podridão parda, quando a inoculação do fungo foi realizada através de ferimentos. Nenhum dos produtos foi eficiente no controle da podridão mole. O ozônio (0,1 mL L-1) não foi eficiente no controle das podridões parda e mole.

SummaryThe timing of sprays for control of peach brown rot (Monilinia fructicola (Wint.) Honey) was re-examined following the introduction of the fungicide benomyl, which has systemic, curative and protective properties. Fifteen different spray schedules of up to four spring and two pre-harvest applications were compared with a post-infection curative schedule.Brown rot did not develop in the experimental orchard until about one month before harvest. Variations in the spring applications had no effect on disease development. Spraying the developing fruit one month before picking was essential for brown rot control in the orchard. Spraying approximately one week before picking did not reduce losses in the orchard. This late spray was necessary however, for control of brown rot in stored fruit.Brown rot control with the curative schedule was equal to that with the best protective schedules but benomyl did not prevent infection of injured fruits.The incidence of soft rot (caused by Rhizopus stolonifer (Fr.) Lind.) in stored fruit was increased by two pre-harvest applications of benomyl.An infection period 18 days before harvest appeared to result in a high level of short-term, latent infection. The rationale of spray schedules is discussed in relation to recent advances in understanding of brown rot epidemiology.

Brown rot, caused by the pathogen Monilinia fructicola, is an economically important disease of peach, Prunus persica. The disease infects fruit, resulting in rots that render the fruit unmarketable. This report evaluates the efficacy of several demethylation inhibitor preharvest fungicides for the control of brown rot in Watkinsville, Georgia (U.S.A.), on a block of ‘O'Henry’ peaches in 2024. The results of this trial will help peach growers make better management decisions for control of brown rot. Of the materials applied, Cevya (mefentrifluconazole) and Tebucon (tebuconazole) provided the best control of brown rot, being comparable to the chemical standard Merivon (fluxapyroxad + pyraclostrobin).