The bacterial blight is a re-emerging disease, severely affecting the productivity of walnut groves. Disease symptoms are observed on all aerial parts of the host plant, but the most damaging are the necrotic spots developing on fruits, leading to massive fruit drops, mainly before endocarp hardening. The causal agent is Xanthomonas arboricola pv. juglandis (Xaj), a gram-negative rod with a worldwide distribution. The population structure of Xaj includes several morphotypes, at least five sequence types, and other features confirming its genomic heterogeneity. Copper resistance is widespread and very effective among Xaj populations: therefore, disease management based on copper sprays is not particularly effective, even in cases of 10-14 treatments during the growing season. The recent, severe outbreaks reported in Italy are due to two concomitant events: i) the rapid increase of walnut acreage, especially in the northern part of the Country and ii) the development of Xaj populations showing high resistance to copper. Since most of the cultivated walnut varieties are either highly susceptible or susceptible to the disease, we tried to implement control strategies based on the use of a single antagonist or the field application of microbial consortia. Additionally, innovative agrochemicals, with a reduced copper content, have also been used. Results showed that: i) microbial biocontrol agents were able to significantly reduce the disease in the field; ii) innovative agrochemicals may reduce the bacterial blight, but might enhance phytotoxicity; iii) a significant reduction of copper inputs is possible, coupled with an effective disease control in walnut groves.

BIOCONTROL OF THE BACTERIAL BLIGHT OF WALNUT: IS THERE A CHANCE TO REDUCE COPPER INPUTS INTO WALNUT GROVES? / Giovanardi, Davide; Fagioli, Luca; Gilli, Lorenzo; Stefani, Emilio. - In: JOURNAL OF PLANT PATHOLOGY. - ISSN 2239-7264. - 99:1 SUP(2017), pp. 49-50. (Intervento presentato al convegno XXIII Convegno Nazionale Società Italiana di Patologia Vegetale - SIPaV tenutosi a Piacenza nel Ottobre 4-6, 2017) [10.4454/jpp.v99i1SUP.3946].

BIOCONTROL OF THE BACTERIAL BLIGHT OF WALNUT: IS THERE A CHANCE TO REDUCE COPPER INPUTS INTO WALNUT GROVES?

GIOVANARDI, Davide
Supervision
;
STEFANI, Emilio
Funding Acquisition
2017

Abstract

The bacterial blight is a re-emerging disease, severely affecting the productivity of walnut groves. Disease symptoms are observed on all aerial parts of the host plant, but the most damaging are the necrotic spots developing on fruits, leading to massive fruit drops, mainly before endocarp hardening. The causal agent is Xanthomonas arboricola pv. juglandis (Xaj), a gram-negative rod with a worldwide distribution. The population structure of Xaj includes several morphotypes, at least five sequence types, and other features confirming its genomic heterogeneity. Copper resistance is widespread and very effective among Xaj populations: therefore, disease management based on copper sprays is not particularly effective, even in cases of 10-14 treatments during the growing season. The recent, severe outbreaks reported in Italy are due to two concomitant events: i) the rapid increase of walnut acreage, especially in the northern part of the Country and ii) the development of Xaj populations showing high resistance to copper. Since most of the cultivated walnut varieties are either highly susceptible or susceptible to the disease, we tried to implement control strategies based on the use of a single antagonist or the field application of microbial consortia. Additionally, innovative agrochemicals, with a reduced copper content, have also been used. Results showed that: i) microbial biocontrol agents were able to significantly reduce the disease in the field; ii) innovative agrochemicals may reduce the bacterial blight, but might enhance phytotoxicity; iii) a significant reduction of copper inputs is possible, coupled with an effective disease control in walnut groves.
2017
XXIII Convegno Nazionale Società Italiana di Patologia Vegetale - SIPaV
Piacenza
Ottobre 4-6, 2017
Giovanardi, Davide; Fagioli, Luca; Gilli, Lorenzo; Stefani, Emilio
BIOCONTROL OF THE BACTERIAL BLIGHT OF WALNUT: IS THERE A CHANCE TO REDUCE COPPER INPUTS INTO WALNUT GROVES? / Giovanardi, Davide; Fagioli, Luca; Gilli, Lorenzo; Stefani, Emilio. - In: JOURNAL OF PLANT PATHOLOGY. - ISSN 2239-7264. - 99:1 SUP(2017), pp. 49-50. (Intervento presentato al convegno XXIII Convegno Nazionale Società Italiana di Patologia Vegetale - SIPaV tenutosi a Piacenza nel Ottobre 4-6, 2017) [10.4454/jpp.v99i1SUP.3946].
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