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The article reports the first instance of Calonectria henricotiae causing boxwood blight in Switzerland and Italy. The pathogen, which has high temperature tolerance, was previously found in Spain and is now detected in these two countries. The study involved collecting and analyzing boxwood twig samples from various locations to confirm the presence of C. henricotiae, highlighting the importance of understanding its distribution to prevent further spread. The research was funded by the USDA National Institute of Food and Agriculture, and the authors disclosed no conflicts of interest. [Extracted from the article]

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.

Recent epidemics of box (boxwood) blight caused by the fungus Calonectria pseudonaviculata in Hyrcanian forests led to the search for eco-friendly fungicides. Essential oils (EOs) of medicinal plants undoubtedly have been highlighted as a new therapeutic approach. In this study, EOs from Cuminum cyminum, Lavandula angustifolia, Thymus daenensis, Trachyspermum copticum and Hyssopus officinalis were evaluated for their inhibitory activities against C. pseudonaviculata Cy-08 in vitro. Quantitative and qualitative composition variations of the EOs were also analysed by GC–MS. Based on the high inhibitory efficacy and low related EC50, MFC and MIC values, T. copticum, L. angustifolia and Th. daenensis EOs can be mentioned as those providing extraordinary efficacy against Cy-08, respectively. Major chemical components of T. copticum, L. angustifolia and Th. daenensis EOs were thymol, linalyl acetate and thymol, respectively. Thymol and linalyl acetate may be the most effective compounds against C. pseudonaviculata. [ABSTRACT FROM AUTHOR]

Boxwood blight caused by Calonectria pseudonaviculata ( Cps ) is an emerging disease in the United States. It has caused significant loss to the ornamental nursery and landscape industries. In this study, 1547 bacterial strains recovered from recycling irrigation systems were evaluated in vitro and in planta for their biological control efficacy against Cps . Three most potent stains 13A3, 14D5, and 34B6 identified all belonged to Pseudomonas protegens . Strains 13A3 and 14D5 reduced Cps mycelial growth by 95 to 100% in two sets of in vitro experiments including a 48-well plate assay and a dual culture assay. Strain 34B6 also reduced Cps growth by 93% in the 48-well plate assay and 66 to 72% in dual culture plates. In planta , strain 14D5 reduced Cps infection by more than 50%, while strains 13D3 and 34B6 by 40 to 46%. Pseudomonas protegens strains produced antifungal secondary metabolites that reduced Cps growth and infection. Other possible modes of action against boxwood blight are discussed. [ABSTRACT FROM AUTHOR]

Leaf blight symptoms were observed on potted box plants (Buxus sempervirens cv. Suffruticosa and B. microphylla) in a nursery in South Moravia in August 2010. These symptoms were suggestive of box blight on Buxus spp. Characteristics of the visual symptoms, microscopic features, and identification of the isolates using DNA sequencing are described. The causal agent was isolated and identified as Cylindrocladium buxicola Henricot by means of morphological, cultural, and molecular characters. The effect of five commercial fungicides on C. buxicola in vitro was studied. The most effective fungicides (kresoxim-methyl, azoxystrobin, and mancozeb) inhibited conidia germination and mycelial growth (kresoxim-methyl, myclobutanil, and penconazole) of C. buxicola more than 96%.

Leaf blight symptoms were observed on potted box plants (Buxus sempervirens cv. Suffruticosa and B. microphylla) in a nursery in South Moravia in August 2010. These symptoms were suggestive of box blight on Buxus spp. Characteristics of the visual symptoms, microscopic features, and identification of the isolates using DNA sequencing are described. The causal agent was isolated and identified as Cylindrocladium buxicola Henricot by means of morphological, cultural, and molecular characters. The effect of five commercial fungicides on C. buxicola in vitro was studied. The most effective fungicides (kresoxim-methyl, azoxystrobin, and mancozeb) inhibited conidia germination and mycelial growth (kresoxim-methyl, myclobutanil, and penconazole) of C. buxicola more than 96%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Knowing the host range of a pathogen is critical to developing and implementing effective disease management programs. Calonectria pseudonaviculata ( Cps ) is known to attack a number of species, varieties, and cultivars in the genus Buxus as well as three Pachysandra species ( Pachysandra terminalis , Pachysandra procumbens , and Pachysandra axillaris ) and several Sarcococca species, all in the Buxaceae family. The objective of this study was to evaluate non-Buxaceae groundcovers and companion plants commonly associated with boxwood plantings for their susceptibility to Cps . Twenty-seven plant species belonging to 21 families were exposed to different levels of inoculum: 50 to 300 conidia per drop for detached leaf assays and 30,000 to 120,000 conidia per 1 ml for whole-plant assays. Inoculated plants were incubated in humid environments for at least 48 h to facilitate infection. Cps infection and sporulation were observed on 12 plant species: Alchemilla mollis , Arctostaphylos uva-ursi , Brunnera macrophylla , Epimedium × youngianum , Galium odoratum , Geranium sanguineum , Phlox subulata , Tiarella cordifolia , Callirhoe involucrata , Iberis sempervirens , Mazus reptans , and Vinca minor . These results suggest that there may be more hosts of Cps commonly grown in nurseries and landscapes. If corroborated by observations of natural infection, these findings have implications for the Boxwood Blight Cleanliness Program instituted by the National Plant Board and for planning disease mitigation at production and in the landscape.