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Cylindrocladium buxicola (synonym C. pseudonaviculata) is a fungal pathogen of Buxus species, causing ‘box blight’. Under conducive weather conditions disease symptoms can develop rapidly and intensively, causing substantial economic losses. Two genotypes of this pathogen have been introduced in Western Europe, the oldest of which is now also spreading rapidly in Northern America.

As part of our research towards the integrated management this disease, the pathogenicity of isolates of the two known genotypes of C. buxicola was tested on 37 different Buxus species. No differences in pathogenicity were observed between the two genotypes or between different isolates of the main genotype. Consequently, one isolate was selected for further susceptibility trials. All cultivars were affected to some extent when environmental conditions were very conducive, demonstrating the absence of complete resistance. In order to evaluate cultivar susceptibility under more realistic weather conditions, including effects of secondary spread, inoculation trials were conducted under semi-commercial conditions. Healthy plants of 32 Buxus species and cultivars were placed on an outdoor container field in close contact with artificially inoculated B. sempervirens ‘Suffruticosa’ plants. Disease development was assessed weekly using the number of diseased leaves per plant. At the end of each experiment the average lesion size, level of defoliation and amount of stem infection was also evaluated . Disease development was correlated with temperature, relative humidity, rainfall and wind speed. Under semi-practical conditions, disease development was not only weather-dependent but also strongly cultivar dependent. In addition, substantial differences in susceptibility were observed between young and mature leaves.

To better understand how temperature and leaf wetness period affect the infection capacity of C. buxicola, additional inoculation experiments were conducted under controlled environmental conditions. The minimum leaf wetness period for infection was cultivar-dependent. Within each cultivar, this period was also considerably shorter for young leaves compared to mature leaves. In addition, young leaves could be infected at lower temperatures (6-12 °C) than mature leaves (12-17 °C). Based on these results, we believe that both leaf maturation level and temperature affect the minimum leaf wetness period needed for infection. This can - partially - explain the observed weather-dependent susceptibility level of different Buxus cultivars.
Original languageEnglish
Title of host publicationAbstract book 65th International Symposium on Crop Protection
Publication date2013
Publication statusPublished - 2013
Event65th International Symposium on Crop Protection (2013) - Gent, Belgium
Duration: 21-May-201321-May-2013

ID: 2249851