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Integrated management of Verticilium wilt in olive

Rafael M. Jiménez Díaz

Professor of Plant Pathology and President of the Spanish Association for Plant Health (AESaVe); Recipient of the Rey Jaime I Award for environmental protection, Fellow of the American Phytopathological Society

Vascular wilt diseases caused by soilborne Verticillium spp. are some of the most devastating diseases for agriculture production worldwide and cannot be effectively controlled by applying a single control measure. Indeed, Vascular wilt diseases are an example of the need to enact integrated disease management (IDM) strategies for effecti disease control ; IDM strategies take an ecologically based approach to minimizing the lost crop yields caused by disease, combining all control measures available and applying them either simultaneously or in a sequence before and/or after planting. Integrated management of Verticillium wilt diseases is far from simple, as the complexities of the strategy itself are overlaid onto those associated with the etiological and epidemiological characteristics of the disease.

Vascular wilt diseases caused by soilborne Verticillium spp. are some of the most devastating diseases for agriculture production worldwide and cannot be effectively controlled by applying a single control measure. Indeed, Vascular wilt diseases are an example of the need to enact integrated disease management (IDM) strategies for effecti disease control ; IDM strategies take an ecologically based approach to minimizing the lost crop yields caused by disease, combining all control measures available and applying them either simultaneously or in a sequence before and/or after planting. Integrated management of Verticillium wilt diseases is far from simple, as the complexities of the strategy itself are overlaid onto those associated with the etiological and epidemiological characteristics of the disease. Verticillium wilt in olive, caused by Verticillium dahliae, is an example of such complexities. Control of the disease is made difficult by: (i) the long survival of the pathogen in soil; (ii) the ability of the pathogen to infect hundreds of crop plants and weeds by growing confined within the xylem during the parasitic phase and establishing pathogenic or endophytic relationships with the host; (iii) the genetic and virulence diversity of V. dahlia  populations, including a highly virulent and lethal defoliating (D) pathotype; and (iv) the ability of the pathogen to easily spread across short and long distances by means of: (a) planting stock; (b) infested soil; (c) infected plant debris from cultivated or alternative hosts; (d) infested irrigation water; and (e) leaves fallen from trees infected with the D pathotype. An IDM strategy for the management of Verticillium wilt in olive must include the following pre-planting and post-planting measures applied in combination: (i) risk assessment when selecting the planting site; (ii) use of planting stock that has been certified as being free of V. dahlie; (iii) reduction or elimination of V.  dahliae inoculum in soil; (iv) protection of healthy planting material from infection by residual inoculum or inoculum that is dispersed from other sites; (v) use of resistant cultivars and rootstocks; (vi) cultural practices; (vii) soil solarization of affected trees; and (viii) application of organic or biological amendments. The effectiveness of those control measures may be reduced in areas where the D pathotype prevails (such as Andalusia and the Aegean coastal region in Turkey) due to: (i) the lower threshold inoculum density for severe disease caused by the D  pathotype compared with that caused by the non-defoliating (ND) pathotype; (ii) leaves fallen from infected trees, providing a source of inoculum for secondary infections; and (iii) the increased susceptibility of olive cultivars to infections by D V. dahliae compared to the ND pathotype, as well as the lessened ability of the plant to recover from the former . Recovery from V. dahlia infection—whereby the incidence and/or severity of the infection is reduced with each successive year provided that no new infections occur through the root system—is an intriguing phenomenon that provides avenues for the integrated management of the disease by applying control measures that limit the potential for severe disease in young trees and protect the root system of recovered trees from new infections. Potential improvements in the effectiveness of IDM of Verticillium wilt in olive come from scientific and technical advances in risk assessment and prevention, the development and use of cultivars and/or rootstock with greater  resistance to the D pathotype of V. dahlia and other strains that may eventually develop, as well as the effective use of experimentally tested biocontrol agents with proven effectiveness agains the disease. However, application of these advances and control measures requires the involvement of professional plant pathologists who are able to implement the tenets of the concept at the local level. This requirement is currently under threat due to declining university education in Plant Pathology and other disciplines of Plant Health and the lack of professional recognition for planthealth professionals.
Research supported by grant P10-AGR 6082 from the CICE-Junta de Andalucía, Spain; grant AGL2011-24935 from the Ministry of Economy and Competitiveness (Spain), co-financed with FEDER funds from the European Union; and by the Organización Interprofesional del Aceite de Oliva Español (CITOLIVA).

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PRODECA also declares that it reserves the right to delete from its website any content that it considers violates current and applicable legislation.

D’acord amb l’article 17.1 de la Llei 19/2014, la ©Generalitat de Catalunya permet la reutilització dels continguts i de les dades sempre que se'n citi la font i la data d'actualització i que no es desnaturalitzi la informació (article 8 de la Llei 37/2007) i també que no es contradigui amb una llicència específica.