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Weber R.W.S.,Esteburg Fruit Research and Advisory Center
Plant Disease | Year: 2011

During the vegetation period 2010, 353 isolates of Botrytis cinerea from 23 Northern German strawberry, raspberry, highbush blueberry, and redcurrant fields were examined for sensitivity to the benzimidazole derivative thiophanate-methyl and the dicarboximide iprodione, as well as five fungicides currently used against gray mold in Germany. Of all isolates, 40.5% were highly resistant to thiophanate-methyl, 64.0% to iprodione, 45.0% to fenhexamid, 76.8% to trifloxystrobin, 21.5% to boscalid, and 14.7% to cyprodinil. No high resistance to fludioxonil was observed but medium resistance was recorded to fludioxonil as well as cyprodinil (41.1 and 27.2% of all isolates, respectively). In all, 63 isolates were sensitive to all five of the currently registered botryticides whereas 43, 81, 94, 49, and 23 isolates were medium or highly resistant to one, two, three, four, and five fungicides, respectively. Isolates resistant to five fungicides in vitro were capable of causing fruit rot on wounded apple pretreated with any one of the three commercially available products containing fenhexamid, pyraclostrobin plus boscalid, or cyprodinil plus fludioxonil. These results question the sustainability of the current gray mold control strategy relying exclusively on fungicides with specific, single-site modes of action. © 2011 The American Phytopathological Society. Source

Maxin P.,University of Aarhus | Weber R.W.S.,Esteburg Fruit Research and Advisory Center
Journal of Plant Diseases and Protection | Year: 2011

Phacidiopycnis washingtonensis, cause of rubbery rot of apples during long-term storage, was first observed in Denmark in April 2010 on fruits of the 2009 harvest. Hot-water treatments were examined as a possible way to control P. washingtonensis. The effective temperature causing a 50% mortality of infectious spores (conidia) after a 3-min submersion in water was 40.2°C. A significant reduction of rubbery rot was achieved by dipping artificially infected fruit in a water bath at 47-52°C for 3 min. Using naturally infected apples, P. washingtonensis as well as the widespread storage-rot pathogen Neofabraea perennans were effectively controlled by a post-harvest dip at 50°C for 3 min or by a rinse at 55°C for 20 s, followed by cold storage in controlled-atmosphere conditions. In contrast, a treatment of freshly harvested fruits with 1-methylcyclopropene (1-MCP) instead of hot water failed to control P. washingtonensis. Source

Maxin P.,University of Aarhus | Williams M.,University of Aarhus | Weber R.W.S.,Esteburg Fruit Research and Advisory Center
Erwerbs-Obstbau | Year: 2014

In the Lower Elbe region of Northern Germany and in other Northern European fruit production areas, about 80 % of all storage rots of apples are caused by Neofabraea alba and N. perennans. Other pathogens include Colletotrichum acutatum, Monilinia fructigena, Phaci-diopycnis washingtonensis, Neonectria galligena, Botrytis cinerea, Penicillium expansum and Fusarium avenaceum. Hot-water treatments of freshly harvested fruits for 3 min at 50-52 °C gave high efficacies against most of these storage rots except F. avenaceum. Substantial evidence supported a heat shock-induced antimicrobial response rather than a direct killing of fungal inoculum as the principal mode of action of hot-water treatments in apples. Shorter exposures for < 30 s at 55-60 °C also provided good control of fungal storage rots and thereby offer new possibilities for this technology in Northern European fruit production. These possibilities include the integration of a hot-water unit into existing grading lines and the option to treat fruits at different time points, e.g. at harvest, after short-term storage and/or after long-term storage. © 2014 Springer-Verlag Berlin Heidelberg. Source

Leroch M.,University of Kaiserslautern | Plesken C.,University of Kaiserslautern | Weber R.W.S.,Esteburg Fruit Research and Advisory Center | Kauff F.,University of Kaiserslautern | And 2 more authors.
Applied and Environmental Microbiology | Year: 2013

The gray mold fungus Botrytis cinerea is a major threat to fruit and vegetable production. Strawberry fields usually receive several fungicide treatments against Botrytis per season. Gray mold isolates from several German strawberry-growing regions were analyzed to determine their sensitivity against botryticides. Fungicide resistance was commonly observed, with many isolates possessing resistance to multiple (up to six) fungicides. A stronger variant of the previously described multidrug resistance (MDR) phenotype MDR1, called MDR1h, was found to be widely distributed, conferring increased partial resistance to two important botryticides, cyprodinil and fludioxonil. A 3-bp deletion mutation in a transcription factor-encoding gene, mrr1, was found to be correlated with MDR1h. All MDR1h isolates and the majority of isolates with resistance to multiple fungicides were found to be genetically distinct. Multiple-gene sequencing confirmed that they belong to a novel clade, called Botrytis group S, which is closely related to B. cinerea and the host-specific species B. fabae. Isolates of Botrytis group S genotypes were found to be widespread in all German strawberry-growing regions but almost absent from vineyards. Our data indicate a clear subdivision of gray mold populations, which are differentially distributed according to their host preference and adaptation to chemical treatments. © 2013, American Society for Microbiology. Source

Batzer J.C.,Iowa State University | Weber R.W.S.,Esteburg Fruit Research and Advisory Center | Weber R.W.S.,University of Aarhus | Mayfield D.A.,Iowa State University | Gleason M.L.,Iowa State University
Mycological Progress | Year: 2016

Sooty blotch and flyspeck (SBFS) is a complex of more than 80 fungal species in 24 genera, mostly belonging to the order Capnodiales within the Dothideomycetes. Colonies of these epiphytes become visible on the surface of apples in mid- to late summer. Several species of SBFS fungi have been previously identified from apples in Germany, but little is known about species diversity, prevalence patterns, or relationship to orchard management practices. To address these questions, apple orchards were surveyed during the 2008 to 2011 seasons in the two largest German apple-growing regions along the Lower Elbe river (northern Germany) and Lake Constance (southern Germany). Using a combination of approaches based on morphology and ITS sequence data, 19 known or putative SBFS species were found, of which 10 belonged to Capnodiales. Abandoned orchards harboured a higher species diversity than organically managed orchards, and no SBFS disease was seen in orchards under integrated pest management. Peltaster cerophilus was the most common SBFS fungus, being associated with 96 and 84 % of SBFS-affected apples sampled from northern and southern German organic orchards, respectively. Microcyclosporella mali and Cyphellophora sessilis were the next most commonly found SBFS species in northern and southern Germany, respectively. Schizothyrium pomi was the only cause of the flyspeck mycelial type of SBFS disease in Germany. © 2015, German Mycological Society and Springer-Verlag Berlin Heidelberg (outside the USA). Source

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