In western Colorado, Cytospora leucostoma is ubiquitous in peach orchards and has developed into a major limiting factor of peach production. The pathogen is unable to invade healthy intact phloem tissue of the tree, but instead, it requires a wound as a mode of entry. Bark injuries caused by cold and pruning in commercial orchard systems provide infection courts that, in suitable environment conditions, can lead to many successful fungal infections. Preventive fungicide control is an integral component of management in tree fruit production. Eighteen fungicides were tested at selected label dose rates for C. leucostoma control. All treatments were initially tested in vitro in fungicide-amended media dishes. Successful treatments were then tested under controlled conditions on detached peach branch segments. Effective fungicides identified in the laboratory assays (thiophanate-methyl, captan, lime sulfur, and copper hydroxide) were further tested as spray applications in the field and as wound sealant applications in combination with latex paint and kaolin clay. Of the treatments evaluated, thiophanate-methyl, captan, 50% latex paint, thiophanate-methyl amended in 50% latex paint, captan amended in 50% latex paint, and lime sulfur were most effective in reducing C. leucostoma necrotic area. Copper hydroxide was ineffective in all field trials and in some instances, yielded larger necrotic areas than the nontreated positive control shoots.
In tropical and subtropical regions worldwide, diseases can be major limiting factors to coffee (Coffea arabica) production, a highly valued crop internationally. Our aim was to identify Colletotrichum spp. and other fungal species associated with Coffee Berry Disease (CBD) and anthracnose on coffee twigs, which can greatly inhibit crop production. Concatenated phylogenetic analyses of ApMat and GS loci were used to identify two Colletotrichum species. Colletotrichum siamense was isolated from symptomatic mature and green berries that were both infested and uninfected with Coffee Berry Borer (CBB) and from twigs displaying anthracnose symptoms. Colletrotrichum alienum was isolated from twigs showing anthracnose symptoms. Along with these two Colletotrichum species, association of Fusarium incarnatum (= Fusarium semitectum) and Fusarium solani was found. Identification of Fusarium species was obtained through combined datasets of partial TEF1 and RPB2. Fusarium isolates came from ripe coffee fruits displaying symptoms of CBD, infested or not with CBB, and coffee twigs. In addition, concatenation of four gene regions (ITS, TEF1, CAL, TUB2) allowed the identification of another fungus, together with isolates from coffee twigs with anthracnose, Diaporthe pseudomangiferae. This is the first report of Colletotrichum siamense and Colletotrichum alienum, along with the fungi Fusarium solani and Diaporthe pseudomangiferae, associated with berry diseases on Coffea arabica in the state of Mérida, Venezuela.
Cytospora canker is one of the most important diseases affecting peach production in Colorado, yet previous efforts to characterize Cytospora species diversity in Colorado have relied exclusively on morphological traits. Recently, several new Cytospora species were described from peach orchards within the United States using molecular and morphological data, prompting the need to reexamine Cytospora spp. present on peach trees in Colorado. A total of 137 isolates of Cytospora spp. were collected from eight orchards in western Colorado. Isolates were sequenced at the ITS (internal transcribed spacer) region and EF1a (elongation factor 1 alpha) and assessed with reference sequences in phylogenetic analyses. All isolates from western Colorado peach trees resolved with the newly described Cytospora plurivora. In addition to molecular characterization, temperature growth and virulence assays were conducted to assess phenotypic variation among the isolates from western Colorado. Variation across isolates was found both in growth at different temperatures and in virulence. Ancestral state reconstruction analyses resolved the most virulent (and most often collected) haplotypes together in a well-supported clade from which a single monophyletic origin of high virulence can be inferred. Finally, a droplet digital PCR assay was developed for use in ongoing and future studies to detect and quantify C. plurivora from field and laboratory samples.
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