Epidemiological Study of Hazelnut Bacterial Blight in Central Italy by Using Laboratory Analysis and Geostatistics

Abstract

Incidence of Xanthomonas arboricola pv. corylina, the causal agent of hazelnut bacterial blight, was analyzed spatially in relation to the pedoclimatic factors. Hazelnut grown in twelve municipalities situated in the province of Viterbo, central Italy was studied. A consistent number of bacterial isolates were obtained from the infected tissues of hazelnut collected in three years (2010–2012). The isolates, characterized by phenotypic tests, did not show any difference among them. Spatial patterns of pedoclimatic data, analyzed by geostatistics showed a strong positive correlation of disease incidence with higher values of rainfall, thermal shock and soil nitrogen; a weak positive correlation with soil aluminium content and a strong negative correlation with the values of Mg/K ratio. No correlation of the disease incidence was found with soil pH. Disease incidence ranged from very low (<1%) to very high (almost 75%) across the orchards. Young plants (4-year old) were the most affected by the disease confirming a weak negative correlation of the disease incidence with plant age. Plant cultivars did not show any difference in susceptibility to the pathogen. Possible role of climate change on the epidemiology of the disease is discussed. Improved management practices are recommended for effective control of the disease.

Eight principles of integrated pest management

“…Fertilization is known to affect sap-sucking insects and mites (Altieri and Nicholls 2003), plant pathogenic fungi (Snoeijer et al 2000), and bacteria (Lamichhane et al 2013). Mechanical weeding can damage crop tissue and favor diseases (Hatcher and Melander 2003).…”

Bacterial Diseases of Crops

“…Schoeneweiss (1981Schoeneweiss ( , 1975 described how environmental stresses, in particular water stress (drought) and freeze, predispose woody plants to the attacks of secondary pathogens. Field disease incidence of hazelnut bacterial blight disease increased with increasing rainfall and soil nitrogen content (Lamichhane et al, 2013). Also, frost events followed by freezing and thawing phenomena, caused by severe fluctuations of day/night temperature, are reported to trigger bacterial infections on a variety of woody crop species, worldwide, leading sometimes to severe plant disease epidemics (Ferrante et al, 2012;Lamichhane et al, 2013;Vigoroux, 1989;Zhao et al, 2013).…”

“…Organic amendments improve soil functions such as infiltration, water-holding capacity, nutrient retention, and release allowing root system to expand. The presence of compact clay soil hinders root system expansion causing water stress and predisposing plants to pathogen attacks (Lamichhane et al, 2013;Matthee and Daines, 1968). …”

“…Rarely, there is an overlapping infection and subsequent symptom developments on Prunus spp. Likewise, on hazelnut, economically important bacterial diseases are sudden decline and bacterial blight (Lamichhane et al, 2013;) caused by P. syringae and X. arboricola, respectively. On hazelnut, P. syringae does not have an epiphytic phase nor does it cause leaf symptoms while X. arboricola has an epiphytic phase and causes leaf spots.…”

Spatial distribution of Yellow Sigatoka Leaf Spot correlated with soil fertility and plant nutrition

“…This approach generates more consistent responses to epidemiological aspects of plant diseases because of the aggregate pattern of inoculum and disease, and soil variability in the area (Alves et al 2006). Geostatistics is part of the geographic information system and is one of the most applied techniques to study spatially related data (Alves et al 2009;Lamichhane et al 2013;Li et al 2013). Its application has rapidly expanded in the area of epidemiology and plant disease management (Alves et al 2009), especially for spatial pattern analysis of factors associated with plant diseases, such as mineral nutrition (Pinheiro et al 2008;Uchôa et al 2011).…”