Management of Calonectria pseudonaviculata in Boxwood with Fungicides and Less Susceptible Host Species and Varieties

The Effect of Boxwood Leaf Volatiles on Conidial Germination of Calonectria pseudonaviculata, the Causal Agent of Boxwood Blight

The fungal pathogen Calonectria pseudonaviculata causes boxwood blight and is a significant threat to the boxwood industry, as well as historic boxwood gardens. The pathogen produces conidia in sticky masses that are splash dispersed, which germinate and infect through stomata on the leaves or stems, causing leaf spots and stem lesions. Despite its ability to cause severe infections on boxwood plants, the pathogen often has a low germination rate on artificial media under lab conditions. To identify cues that stimulate germination, we explored whether host factors could induce high germination rates. In this study, we demonstrate that C. pseudonaviculata spores achieve high germination rates when they are placed on detached leaves of boxwood and other known hosts, compared to potato dextrose agar and glass coverslips. We also demonstrate that germination is induced by volatiles from detached leaves of boxwood, as well as the nonhost Berberis thunbergii. When C. pseudonaviculata spores were exposed to volatiles from boxwood leaves in the presence of ethylene scrubber packs that contained potassium permanganate, the stimulatory effect on spore germination was reduced. However, ethylene, a regulator of leaf senescence, did not stimulate germination of C. pseudonaviculata spores. This suggests that the pathogen may have evolved to recognize one or more host volatiles, other than ethylene to induce germination, thus limiting its growth until it senses the presence of a host plant.

Multi-Year Field Plantings Evaluating Boxwood Cultivars for Susceptibility to the Blight Pathogens (Calonectria spp.) in Northern Germany

Two multiyear field trials were conducted to evaluate boxwood cultivars for their susceptibility to the blight pathogens Calonectria pseudonaviculata and C. henricotiae in northern Germany. Fifteen cultivars were included in the first trial from 2007 to 2012, and 46 cultivars were included in the second trial from 2014 to 2017. Both trials were done in a naturally infested field that was supplemented with infected plant tissue added to the soil before planting. Each cultivar had three replicate hedge sections with 10 plants per section, and they were assessed annually for blight severity expressed as proportion of leaves blighted and fallen. Blight severity varied significantly among years (P < 0.0001) and cultivars (P < 0.05) within each trial. In the first trial, mean severity ranged from 0.03 to 0.11 for the most resistant cultivars and 0.35 to 0.96 for the most susceptible ones. Similarly, in the second trial, mean severity ranged from 0.06 to 0.27 and 0.71 to 0.97 for the most resistant and susceptible cultivars, respectively. 'Suffruticosa' was consistently the most susceptible cultivar, followed by 'Marianne', 'Myosotidifolia', 'Raket', and 'Morris Midget'. 'Herrenhausen' was the most resistant cultivar, followed by B. microphylla var. japonica, B. microphylla var. koreana, 'Green Mound', 'Faulkner', and 'Winter Beauty'. This study provides field data showing the performance of boxwood cultivars under different levels of disease pressure in an area where C. henricotiae was dominant. This knowledge will help boxwood growers and gardeners to choose less susceptible cultivars and help plant breeders to select for disease resistance.

Effect of Temperature, Leaf Wetness Period, and Cultivar Susceptibility on Boxwood Blight Disease Development and Sporulation

Boxwood blight causes great losses to the boxwood nursery industry and landscapes in 30 states in the United States. Understanding the epidemiological factors governing disease development will be important for disease forecasting and design of best management practices. We evaluated the effect of leaf wetness period (lwp) and temperature on lesion development and sporulation on three boxwood cultivars under controlled conditions to develop predictive models for disease development. We conducted detached leaf assays at 18 to 27°C and various lwp with the cultivars Buxus sempervirens 'Suffruticosa' (highly susceptible), B. sempervirens × B. microphylla var. koreana 'Green Velvet' (moderately susceptible), and B. microphylla var. japonica 'Winter Gem' (less susceptible). Detached leaves were inoculated with 200 conidia in 50 µl of suspension and disease incidence was recorded at 3 to 13 days postinoculation (dpi). Cultivar, lwp, temperature, and most interactions significantly influenced disease development. A minimum of 5 h of leaf wetness was required for any disease. Lesion development increased most rapidly between 12 and 15 h and continued to increase to about 21 h of leaf wetness. Temperatures between 21 and 25°C were optimal for lesion development. There was about a 7-day lag between appearance of lesions and maximal incidence of sporulation. The two less-susceptible cultivars had fewer lesions than Suffruticosa under the same infection conditions; in addition, leaf lesions of Winter Gem exhibited delayed sporulation and sporulation from a smaller proportion of symptomatic leaves. Response surfaces were developed for each cultivar to predict the disease incidence using the lwp and dpi. Our findings will help refine disease forecast models to improve management of boxwood blight.

Cool Temperatures Favor Growth of Oregon Isolates of Calonectria pseudonaviculata and Increase Severity of Boxwood Blight on Two Buxus Cultivars

Controlled environment experiments were conducted to evaluate the effects of temperature on Calonectria pseudonaviculata mycelial growth and the effects of temperature and infection period on boxwood blight severity. In experiment 1, 15 Oregon isolates (representing five genotypes) were grown on potato dextrose agar (PDA) and malt extract agar (MEA) at six temperatures from 5 to 30°C. Growth (culture diameter) was measured after 2 weeks. Optimal growth occurred at 25°C on PDA and 20°C on MEA. Isolates of genotype G1 also grew faster than genotype G2, but only on MEA at 25°C. In experiment 2, Buxus cultivars Green Velvet (GV, more susceptible) and Winter Gem (WG, more resistant) were inoculated and incubated in moist chambers for 9 or 24 h at 22°C (infection period), then moved into growth chambers at 15 or 25°C. After 4 weeks, chamber temperatures were switched, and plants were incubated for 4 more weeks. Disease severity was evaluated weekly. During the first 4 weeks, disease was generally more severe on GV than WG, on plants with a 24-h versus a 9-h infection period, and on plants incubated at 15°C versus 25°C. However, disease was just as severe on WG as GV when the 24-h infection period was followed by incubation at 15°C. After the temperatures were switched, disease increased only on WG that were cooled from 25 to 15°C. Results show that Oregon isolates of C. pseudonaviculata are capable of growing faster and causing more severe disease at temperatures cooler than those reported previously.

Impact of Calonectria Diseases on Ornamental Horticulture: Diagnosis and Control Strategies

Diseases caused by fungi in the genus Calonectria pose a significant threat to the ornamental horticulture industries in Europe and the United States. Calonectria spp. are particularly challenging pathogens to manage in ornamental production systems and the urban landscape for multiple reasons. A high level of species diversity and poorly resolved taxonomy in the genus makes proper pathogen identification and disease diagnosis a challenge, though recent molecular phylogenetic studies have made significant advances in species delimitation. From a disease management perspective, Calonectria spp. produce long-lived survival structures (microsclerotia) that contaminate nursery production systems and can survive multiple years in the absence of a susceptible plant host. Latent infection of plant material is poorly understood but likely contributes to long-distance dissemination of these fungal pathogens, including the clonal Calonectria spp. responsible for the global emergence of boxwood blight. Breeding for disease resistance represents a sustainable strategy for managing Calonectria diseases but is challenging due to the perennial nature of many ornamental plants and high levels of susceptibility in commercial cultivars. Ultimately, long-term sustainable management of Calonectria diseases will require an improved understanding of pathogen biology as well as integration of multiple disease management strategies.

Potential Distribution of Invasive Boxwood Blight Pathogen (Calonectriapseudonaviculata) as Predicted by Process-Based and Correlative Models

Boxwood blight caused by Cps is an emerging disease that has had devastating impacts on Buxus spp. in the horticultural sector, landscapes, and native ecosystems. In this study, we produced a process-based climatic suitability model in the CLIMEX program and combined outputs of four different correlative modeling algorithms to generate an ensemble correlative model. All models were fit and validated using a presence record dataset comprised of Cps detections across its entire known invaded range. Evaluations of model performance provided validation of good model fit for all models. A consensus map of CLIMEX and ensemble correlative model predictions indicated that not-yet-invaded areas in eastern and southern Europe and in the southeastern, midwestern, and Pacific coast regions of North America are climatically suitable for Cps establishment. Most regions of the world where Buxus and its congeners are native are also at risk of establishment. These findings provide the first insights into Cps global invasion threat, suggesting that this invasive pathogen has the potential to significantly expand its range.

Comparative Performance of Sanitizers in Managing Plant-to-Plant Transfer and Postharvest Infection of Calonectria pseudonaviculata and Pseudonectria foliicola on Boxwood

Calonectria pseudonaviculata and Pseudonectria foliicola causing the infamous "boxwood blight" and "Volutella blight," respectively, are a constant threat to the boxwood production and cut boxwood greenery market. Both pathogens cause significant economic loss to all parties (growers, retailer, and customers) in the horticultural chain. The objective of this study was to evaluate efficacy of disinfesting chemicals (quaternary ammonium compound [QAC], peroxy, acid, alcohol, chlorine, and cleaner) in preventing plant-to-plant transfer of C. pseudonaviculata and P. foliicola via cutting tools, as well as reduction of postharvest boxwood blight and Volutella blight disease severity in harvested boxwood greenery. First, an in vitro study was conducted to select products and doses that completely or near-completely inhibited conidial germination of C. pseudonaviculata and P. foliicola. The selected treatments were also tested for their ability to reduce plant-to-plant transfer of C. pseudonaviculata and P. foliicola and manage postharvest boxwood blight and Volutella blight in boxwood cuttings. For the plant-to-plant transfer study, Felco 19 shears were used as a tool for mechanical transfer of fungal conidia. The blades of Felco 19 shears were exposed to a conidial suspension of C. pseudonaviculata or P. foliicola by cutting a 1-cm-diameter cotton roll that had been dipped into a fungal suspension. Disease-free boxwood rooted cuttings (10-cm height) were pruned with the contaminated shears. The Felco 19 shears were equipped with a mounted miniature sprayer connected to a pressurized reservoir of treatment solution that automatically sprayed the blade and plant surface while cutting. The influence of accumulated sap on the shear blade was studied through 1- or 10-cut pruning variable on test plants and screened for the efficacy of treatments. Then, the boxwood rooted cuttings were transplanted and incubated in room conditions (21°C, 60% RH) with 12 h of fluorescent light; data evaluation on disease severity was done weekly for a month. Disease progress (area under disease progress curve [AUDPC]) was calculated. In another study, postharvest dip application treatments were used for the management of postharvest boxwood blight or Volutella blight on boxwood cuttings. The harvested boxwood cuttings were inoculated with a conidial suspension of C. pseudonaviculata or P. foliicola and then dipped into treatment solution 3 days afterward. The treated boxwood cuttings were kept in room conditions, and boxwood blight or Volutella blight disease severity as well as marketability (postharvest shelf life) was assessed every 2 days for 1 week. A significant difference between treatments was observed for reduction of boxwood blight or Volutella blight severity and AUDPC. The treatments [Octyl decyl dimethyl (ODD) + dioctyl dimethyl (DoD) + didecyl dimethyl (DdD) + dimethyl benzyl (DB)] ammonium chloride (AC) (Simple Green D Pro 5), 2-propanol + didecyl dimethyl ammonium chloride (DDAC) (0.12%; KleenGrow), and dimethyl benzyl ammonium chloride (DBAC) + dimethyl ethylbenzyl ammonium chloride (DEAC) (GreenShield) were the most effective in reducing the plant-to-plant transfer of boxwood blight and Volutella blight when pruned with contaminated Felco 19 shears. In addition to the three effective treatments above, acetic acid (2.5%; vinegar), 2-propanol + DDAC (0.06%), sodium hypochlorite (Clorox), and potassium peroxymonosulfate + NaCl (2%; Virkon) were effective in reducing postharvest boxwood blight, whereas DBAC + DBAC (Lysol all-purpose cleaner), ethanol (70% [ethyl alcohol]), and DDAC + DBAC (Simple Green D Pro 3 plus) were effective in reducing Volutella blight disease severity and AUDPC, and they also maintained better quality and longer postharvest shelf life of boxwood cuttings when applied as a dip treatment. The longer postharvest shelf life of boxwood cuttings noted may be attributed to reduced disease severity and AUDPC resulting in healthy boxwood cuttings.

Evidence for the Role of CYP51A and Xenobiotic Detoxification in Differential Sensitivity to Azole Fungicides in Boxwood Blight Pathogens

Boxwood blight, a fungal disease of ornamental plants (Buxus spp.), is caused by two sister species, Calonectria pseudonaviculata (Cps) and C. henricotiae (Che). Compared to Cps, Che is documented to display reduced sensitivity to fungicides, including the azole class of antifungals, which block synthesis of a key fungal membrane component, ergosterol. A previous study reported an ergosterol biosynthesis gene in Cps, CYP51A, to be a pseudogene, and RNA-Seq data confirm that a functional CYP51A is expressed only in Che. The lack of additional ergosterol biosynthesis genes showing significant differential expression suggests that the functional CYP51A in Che could contribute to reduced azole sensitivity when compared to Cps. RNA-Seq and bioinformatic analyses found that following azole treatment, 55 genes in Cps, belonging to diverse pathways, displayed a significant decrease in expression. Putative xenobiotic detoxification genes overexpressed in tetraconazole-treated Che encoded predicted monooxygenase and oxidoreductase enzymes. In summary, expression of a functional CYP51A gene and overexpression of predicted xenobiotic detoxification genes appear likely to contribute to differential fungicide sensitivity in these two sister taxa.

Comparative analysis of extracellular proteomes reveals putative effectors of the boxwood blight pathogens, Calonectria henricotiae and C. pseudonaviculata

Calonectria henricotiae (Che) and C. pseudonaviculata (Cps) are destructive fungal pathogens causing boxwood blight, a persistent threat to horticultural production, landscape industries, established gardens, and native ecosystems. Although extracellular proteins including effectors produced by fungal pathogens are known to play a fundamental role in pathogenesis, the composition of Che and Cps extracellular proteins has not been examined. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and bioinformatics prediction tools, 630 extracellular proteins and 251 cell membrane proteins of Che and Cps were identified in the classical secretion pathway in the present study. In the non-classical secretion pathway, 79 extracellular proteins were identified. The cohort of proteins belonged to 364 OrthoMCL clusters, with the majority (62%) present in both species, and a subset unique to Che (19%) and Cps (20%). These extracellular proteins were predicted to play important roles in cell structure, regulation, metabolism, and pathogenesis. A total of 124 proteins were identified as putative effectors. Many of them are orthologs of proteins with documented roles in suppressing host defense and facilitating infection processes in other pathosystems, such as SnodProt1-like proteins in the OrthoMCL cluster OG5_152723 and PhiA-like cell wall proteins in the cluster OG5_155754. This exploratory study provides a repository of secreted proteins and putative effectors that can provide insights into the virulence mechanisms of the boxwood blight pathogens.

Can Biological Control Agents Reduce Multiple Fungal Infections Causing Decline of Milkwort in Ornamental Nursery?

This research evaluates biological control agents (BCAs) and fungicide alone and in combination for the management of decline caused by multiple fungi on milkwort (Polygala myrtifolia). Four experiments were performed in a greenhouse within a nursery located in Catania province (southern Italy). The activity of fungicides and biological control agents was evaluated by calculating the plant mortality (%) and recovery frequency (%) of different fungi associated with symptomatic tissue. Comprehensively, boscalid + pyraclostrobin and fosetyl-Al showed the best results in managing disease complex on milkwort. Biological control agents provided, on average, the lowest performances; nevertheless, in most cases, they were able to significantly reduce multiple infections and sometimes when combined with fungicide enhanced the effectiveness. The molecular analysis of 86 isolates obtained from symptomatic tissue allowed to identify the fungi involved in the disease as Calonectriapauciramosa, C. pseudomexicana, Fusariumoxysporum, Neocosmospora solani (syn. F. solani) and binucleate Rhizoctonia AG-R. Calonectriapseudomexicana never reported on milkwort and in Europe was inoculated on P. myrtifolia potted healthy cuttings and produced crown and root rot after 40 days. Our findings represent the first worldwide report about disease complex of milkwort caused by several fungi (Calonectria spp., Fusarium spp. and binucleate Rhizoctonia) and on the effects of integrated control strategies to manage this disease in the nursery.

A Potent Burkholderia Endophyte against Boxwood Blight Caused by Calonectria pseudonaviculata

Calonectria pseudonaviculata (Cps) poses an increasing threat to boxwood, a major nursery crop and iconic landscape plant worldwide. Here, we report on a potent biocontrol agent that produces small sage green (SSG) colonies on potato dextrose agar. SSG is a bacterial strain recovered from Justin Brouwers boxwood leaves with unusual response to Cps inoculation. Water-soaked symptoms developed on leaves 2 days after inoculation then disappeared a few days later. This endophyte affected several major steps of the boxwood blight disease cycle. SSG at 10⁷ cfu/mL lysed all conidia in mixed broth culture. SSG at 10⁸ cfu/mL reduced blight incidence by >98% when applied one day before or 3 h after boxwood were inoculated with Cps. Its control efficacy decreased with decreasing bacterial concentration to 10³ cfu/mL and increasing lead time up to 20 days. When applied on diseased leaf litter under boxwood plants, SSG reduced Cps sporulation and consequently mitigated blight incidence by 90%. SSG was identified as a new member of the Burkholderia cepacia complex with distinct characters from known clinical strains. With these protective, curative, and sanitizing properties, this Burkholderia endophyte offers great promise for sustainable blight management at production and in the landscape.

Widespread Occurrence of a CYP51A Pseudogene in Calonectria pseudonaviculata

Calonectria pseudonaviculata and C. henricotiae are two closely related fungal species responsible for boxwood blight disease of ornamental shrubs (Buxus spp.) in the U.S. and Europe. A previous study has shown isolates of the latter species, which is restricted to Europe, to be less sensitive to tetraconazole, an azole fungicide. In this study, we have analyzed the CYP51 paralogs for polymorphism in 26 genomes, representing geographically disparate populations of C. pseudonaviculata (n = 19) and C. henricotiae (n = 7), from the U.S., Europe, Asia, and New Zealand. The presence of a CYP51A pseudogene and lack of a functional CYP51A paralog in all C. pseudonaviculata genomes examined is a novel discovery for fungi and could have implications for the evolution of resistance to antifungal chemicals.

Boxwood Blight: Threat to Ornamentals

Boxwood blight, caused by Calonectria pseudonaviculata and Calonectria henricotiae, has had devastating effects in gardens since its first appearance in the United Kingdom in 1994. The disease affects two other plants in the Buxaceae: sweet box (Sarcococca spp.) and pachysandra (Pachysandra spp.). C. pseudonaviculata was likely introduced to Europe by nursery trade from East Asia on an ornamental species and then to western Asia and North America. Thus far, C. henricotiae has been seen only in Europe. Boxwood, valued at $126 million wholesale per year in the United States alone, is now besieged by an aggressive foliar blight active over a broad temperature range when there are long periods of leaf wetness. Research on inoculum, means of dissemination, cultivar susceptibility, environmental influences, fungicides, sanitizers, and detection methods has vastly improved knowledge of this new invasive disease in a short time. Boxwood with genetic resistance to the disease is critically needed.

Preventing Soil Inoculum of Calonectria pseudonaviculata from Splashing onto Healthy Boxwood Foliage by Mulching

Boxwood blight, caused by Calonectria pseudonaviculata, is an emerging disease of great concern to horticulturists in the United States and other affected countries. The objective of this study was to evaluate the efficacy of mulching as a physical barrier to prevent soil inoculum from splashing onto healthy boxwood foliage. A field trial consisting of two treatments, mulched and nonmulched, was conducted under field conditions in Lowgap, North Carolina, and in a residential landscape setting near Richmond, Virginia, for 2 years at each site. Mulching efficacy was assessed by monitoring and comparing boxwood blight development on detector plants: containerized 'Justin Brouwers' boxwood, which were rotated through mulched and nonmulched plots at 1- and 2-week intervals in the Lowgap and Richmond sites, respectively. Boxwood blight was observed on detector plants in a combined 55 of the 88 monitoring periods during this study at the two sites. Mulching provided complete protection of Justin Brouwers boxwood from infection by C. pseudonaviculata soil inoculum during 33 of the 55 positive monitoring periods (60%) and good to excellent protection during 13 monitoring periods (24%). The potential applications of mulching for boxwood blight mitigation are discussed.

Effects of Sublabeled Rates of Dazomet and Metam-Sodium Applied Under Low-Permeability Films on Calonectria Microsclerotia Survival

Infested soil is the primary inoculum source for Calonectria spp. for initiating disease in ornamental and forestry crops. The effects of dazomet and metam-sodium on survival of microsclerotia of 28 isolates belonging to 19 Calonectria spp. were evaluated in this study under nursery conditions. Two experiments with exotic Calonectria spp. in plastic containers in a greenhouse and three trials with endemic species in field plots were performed during different seasons. The containers and plots were artificially infested with Calonectria microsclerotia differentiated on carnation leaf tissues. Basamid (dazomet) was applied at 100, 160, 200, 400, and 500 kg/ha, while Divapan (metam-sodium) was applied at 250, 350, 400, 700, and 1,000 liters/ha in both the containers and plots. The fumigants were applied under virtually and totally impermeable films. Fungal survival was evaluated after 21 days using leaf tissues collected from treated soil and plated on potato dextrose agar, and the ability of microsclerotia to cause infection was tested on red clover. The survival of Calonectria inocula and microsclerotia decreased with increasing fumigant rates. In the greenhouse trials, where Basamid was applied at 200, 400, and 500 kg/ha and Divapan at 400, 700, and 1,000 liters/ha, no viable microsclerotia were recovered for 14 exotic Calonectria spp., whereas viable inocula of Calonectria hongkongensis, C. naviculata, and C. sulawesiensis were retrieved from the fumigated plots. Low rates of Basamid (100 and 160 kg/ha) and Divapan (250 and 350 liters/ha) were less effective at reducing Calonectria viability and, for these treatments, the rate of microsclerotia survival was highly variable among the different isolates and species. Furthermore, totally impermeable film significantly enhanced fumigant performance. Relative to endemic Calonectria spp., all of the treatments killed microsclerotia of C. polizzii and C. pauciramosa independent from fumigant, rate, and film. This research demonstrated the possibility of reducing the application rates by up to 160 kg/ha for Basamid and 400 liters/ha for Divapan under low-permeability films (virtually impermeable film or totally impermeable film) for eradicating or reducing the primary inoculum of Calonectria spp. in soil.

Effects of Inoculum Dose, Temperature, Cultivar, and Interrupted Leaf Wetness Period on Infection of Boxwood by Calonectria pseudonaviculata

Boxwood blight is an emerging disease of great concern for the ornamental horticulture industry, historic garden managers, landscapers, and homeowners. Controlled-environment experiments were conducted to determine the effects of conidial concentration, temperature, interrupted leaf wetness period, cultivar, and leaf age on infection of boxwood leaves by Calonectria pseudonaviculata. Boxwood blight incidence (BBI) increased with increasing concentration up to 2.0 × 10⁴ spores/ml. BBI also increased as temperature increased from 18 to 25°C, then declined gradually to zero at 29°C. Similar infection effects of inoculum concentration were observed in an experiment with four boxwood cultivars ('Justin Brouwers', 'John Baldwin', 'Green Mound', and 'Nana') of various degrees of susceptibility. The hypothesis that younger leaves are more susceptible than older leaves was supported for Justin Brouwers and Nana but not for Green Mound; and younger leaves of John Baldwin were less susceptible than older leaves. When inoculated plants ('Suffruticosa') were exposed to dry interruptions of 3 h or longer between 5 or 8 h of initial wetness and 12 h of additional wetness, these plants had significantly lower BBI compared with those exposed to continuous wetness for 20 h, and similar or at most slightly more infection than plants exposed to only the 5- or 8-h initial wetness. Continuous wetness durations beyond 20 h did not increase infection in these experiments. These results advanced our understanding of the environmental requirements of the infection process in boxwood blight development and they are essential for refining disease forecasting models.

Integrated Management for the Reduction of Calonectria Infections in Ornamental Nurseries

Chemical control represents the main effective strategy for managing Calonectria diseases in ornamental nurseries. The occurrence of fungicide-resistant strains and the European Directive on "Sustainable Use of Pesticides" has forced ornamental plant growers to establish effective integrated pest management strategies to control Calonectria infections. Here, three nursery experiments were performed to detect the best combinations of fungicides and biological control agents (BCA) to control both leaf spot, caused by six Calonectria spp. on bottlebrush and metrosideros, and stem rot, caused by Calonectria morganii on Dodonaea plants. Overall, the cyprodinil + fludioxonil mixture alone or combined with bioformulates containing Bacillus, Trichoderma, and Streptomyces spp. provided the best performance in reducing leaf spot and stem rot caused by Calonectria spp., followed by the mixture of boscalid + pyraclostrobin. Although BCA alone provided disease suppression significantly lower than the controls in most cases, these treatments were, on average, the least effective in controlling Calonectria infections. Otherwise, there were no significant increases in efficacy with fungicides plus BCA over fungicides alone. Thus, the application of boscalid + pyraclostrobin and cyprodinil + fludioxonil mixtures may also be used in large-scale applications to reduce Calonectria diseases because they effectively managed leaf and stem infections. Our comprehensive research applied previously acquired information on Calonectria disease management in nurseries, resulting in important data that affects integrated plans to fight these pathogens in accordance with European legislation.