[en] The infestation of irrigation waters by Verticillium dahliae poses a risk for the health of susceptible crops in Andalusia. Spread of conidia and sclerotia of the pathogen via irrigation water has contributed to enlarge the extension and epidemic development of the Verticillium wilt of olive (VWO) throughout this region. The application of chemical disinfectants into the irrigation water has proved to be useful suppressing infestations by V. dahliae conidia. To ascertain the effect against sclerotia -more persistent structures of the fungus- is required before recommending this practice as an exclusion measure within the integrated management of the VWO. Furthermore, the fate of this treated water would be the rhizosphere, so this measure could contribute to eradicate the fungus in the soil and/or reduce the disease in infested olive orchards. The first goal of the present thesis was to evaluate the in vitro efficacy of chemical disinfestation in preventing and eradicating water infestations by V. dahliae sclerotia. Three products differing in composition (OX-VIRIN&reg;, OX-AGUA AL25&reg;, and Deccoklor&reg;) were tested according to the concentration, V. dahliae isolate and time of action. The effect of disinfectants OX-VIRIN&reg; (OV) and OXAGUA AL25&reg; (OA), both including hydrogen peroxide in their formulation, varied with the concentration and time. Suppressive efficacy ranged between 87.8- 100% for the three highest concentrations of OV (3.2-51.2 mL L-1) and 99.6-100% for the two highest of OA (0.4175 y 1.2525 mL L-1) at 5-30 days after the treatment of infested water. These OV concentrations showed higher preventive efficacy than OA concentrations against infestations carried out 30 days after the chemical treatment of the water (97-100% vs. 68,9-100%). The chlorinated product Deccoklor&reg; was ineffective. The potential efficacy of OV and OA in reducing the fungus in the soil and the VO in young olive plants was evaluated in several experiments conducted under growth chamber conditions. The soil-applied disinfectant treatments were also assessed for phytotoxicity on olive plants. Susceptible olive cultivars were grown in V. dahliae-infested soil and subjected to different disinfectant treatments with OV- or OA-treated water. The lowest concentrations recommended for disinfesting V. dahliae-containing water according to results from the previous objective were used (3.2 mL L&minus;1 or 0.4175 mL L&minus;1, respectively). The weekly and monthly treatments with OV and the biweekly treatment with OA decreased solidly the total inoculum density in the soil up to 21.3-29.6% and sclerotia density up to 65.6-91.2%, depending on the treatment. These same disinfectant treatments reduced the disease by 0-40.2% and 3-61.4%, depending on the parameter evaluated, on Picual and Arbequina cultivar, respectively. The tested treatments did not negatively affect the plant growth and phytotoxicity was not observed on any cultivar. Irrigation systems of Andalusian olive orchards allow for the treatment of ponded irrigation water, but also within the distribution network by means of metering pumps. The third part of the thesis addressed the efficacy of injecting disinfectants in the irrigation system in reducing the incorporation and accumulation of V. dahliae in the soil according to the product concentration (OV and OA; 3.2-51.2 mL L-1 and 1.25-11.27 mL L-1, respectively), the type of propagule infesting the water (conidia or sclerotia), and the environmental conditions (spring or fall). The injection of OV and OA prevented or reduced above 95% the accumulation of conidia and sclerotia in both seasons, depending on the concentration applied. The disease was not observed, and the infection prevented or markedly reduced in olive plants raised in soil irrigated with infested and treated water. The last objective of the thesis was to assess the efficacy of injecting the disinfectants within the irrigation system for reducing the V. dahliae inoculum density in soil and the VWO in a long-term experiment conducted under natural environmental conditions. The assessment was carried out combining the Picual cultivar, a highly virulent defoliating pathotype of V. dahliae, and different application strategies with OV (3.2 mL L-1)- and OA (3.76 mL L-1)-treated water for two periods comprising from late winter to late summer. Disinfestation reduced the total inoculum density in soil (by 51.2%, on average) and the disease and infection incidence (by 20.0 and 18.4%, respectively, on average). OA applied twice a month in alternate weeks was the strategy that stood out among the rest by reducing the total inoculum and sclerotia density in soil by 75 and 85.4%, respectively, and symptomatology and infection extent by 53 and 70.8%, respectively, with respect to control. Soil disinfestation, especially following the mentioned OA-strategy, promoted a significantly greater tree recovery from the disease and relieved the reduction in tree growth and production that occurred in infested soils. The disinfectants tested in this work not only reduce water infestations by sclerotia, but also the fungus in soil and the VWO when applied at certain concentrations. Their use could be conceived as a complementary practice within the integrated management of the disease in Andalusian orchards or nurseries using V. dahliae-containing water and in those in which the pathogen is already established in the soil. The development of water disinfectants incorporating hydrogen peroxide in their formulation should be encouraged by manufacturers.

[es] La contaminaci&oacute;n de las aguas de riego por Verticillium dahliae supone un riesgo para la sanidad de cultivos susceptibles al pat&oacute;geno en Andaluc&iacute;a. La dispersi&oacute;n de conidias y esclerocios del patotipo defoliante del hongo a trav&eacute;s de este medio, ha contribuido a la extensi&oacute;n y el desarrollo de las epidemias de Verticilosis del olivo (VO) en esta regi&oacute;n. La aplicaci&oacute;n de desinfectantes qu&iacute;micos al agua de riego puede suprimir la infestaci&oacute;n por conidias de V. dahliae, y podr&iacute;a constituir una medida de exclusi&oacute;n dentro del manejo integrado de la VO si se probara tambi&eacute;n su eficacia frente a esclerocios, estructuras de supervivencia del hongo. Adem&aacute;s, dado que el destino final del agua tratada ser&iacute;a la zona de influencia del sistema radicular, esta pr&aacute;ctica podr&iacute;a contribuir a erradicar al hongo en el suelo y/o reducir la enfermedad en olivares infestados. El primer objetivo de esta tesis consisti&oacute; en evaluar in vitro la eficacia de la desinfestaci&oacute;n qu&iacute;mica para prevenir y erradicar infestaciones del agua por esclerocios de V. dahliae. Tres productos de diferente composici&oacute;n (OX-VIRIN&reg;, OX-AGUA AL25&reg; y Deccoklor&reg;) fueron evaluados en funci&oacute;n de la concentraci&oacute;n, el aislado de V. dahliae y el tiempo de acci&oacute;n. El efecto de los productos OX-VIRIN&reg; (OV) y OX-AGUA AL25&reg; (OA), ambos conteniendo per&oacute;xido de hidr&oacute;geno en su formulaci&oacute;n, vari&oacute; con la concentraci&oacute;n y tiempo de acci&oacute;n. La eficacia supresiva en los d&iacute;as posteriores al tratamiento del agua infestada (5-30 d&iacute;as) fue de 87,8-100% para las tres concentraciones m&aacute;s altas de OV (3,2-51,2 mL L-1) y de 99,6-100% para las dos m&aacute;s altas de OA (0,4175 y 1,2525 mL L-1). Estas concentraciones de OV mostraron mayor eficacia preventiva que las de OA frente a infestaciones realizadas 30 d&iacute;as despu&eacute;s del tratamiento qu&iacute;mico del agua (97-100% vs. 68,9-100%). El producto clorado Deccoklor&reg; no fue eficaz. La eficacia potencial de los desinfectantes OV y OA para reducir al hongo en el suelo y la VO se evalu&oacute; en plantas j&oacute;venes bajo ambiente controlado en varios experimentos. El efecto fitot&oacute;xico de las aplicaciones de los desinfectantes al suelo se explor&oacute; tambi&eacute;n sobre la planta. Cultivares de olivo susceptibles Picual y Arbequina fueron crecidos en suelo infestado con V. dahliae y sometidos a diferentes tratamientos desinfestantes con agua tratada a 3,2 mL L&minus;1 de OV o a 0,4175 mL L&minus;1 de OA, concentraciones m&iacute;nimas recomendables para la desinfestaci&oacute;n de agua seg&uacute;n los resultados del primer objetivo. Las aplicaciones semanal y mensual de OV y la quincenal de OA redujeron s&oacute;lidamente la densidad de in&oacute;culo total y de esclerocios del hongo en el suelo en hasta un 21,3-29,6% y 65,6-91,2%, respectivamente, dependiendo del tratamiento. Estas mismas aplicaciones redujeron la enfermedad entre un 0- 40,2% y 3-61,4%, seg&uacute;n el par&aacute;metro evaluado, en los cultivares Picual y Arbequina, respectivamente. Los tratamientos evaluados no afectaron negativamente al crecimiento de los plantones ni se identific&oacute; indicio alguno de fitotoxicidad en ambos cultivares. Los sistemas de riego del olivar andaluz permiten el tratamiento del agua embalsada, pero tambi&eacute;n en la red de distribuci&oacute;n mediante bombas de inyecci&oacute;n. La tercera parte de la tesis abord&oacute; la eficacia de inyectar desinfectantes en el sistema de riego para reducir la incorporaci&oacute;n y acumulaci&oacute;n de V. dahliae en el suelo en funci&oacute;n de la concentraci&oacute;n de los productos (OV y OA; 3,2-51,2 mL L-1 y 1,25-11,27 mL L-1, respectivamente), el tipo de prop&aacute;gulo del hongo presente en el agua (conidias o esclerocios), y las condiciones ambientales (primavera u oto&ntilde;o). La inyecci&oacute;n de OV y OA previno o redujo en m&aacute;s de un 95% la acumulaci&oacute;n de conidias y esclerocios en el suelo en ambas estaciones seg&uacute;n la concentraci&oacute;n aplicada. La enfermedad no fue observada y la infecci&oacute;n fue prevenida o marcadamente reducida en plantones de olivo crecidos en el suelo regado con agua infestada y tratada. El &uacute;ltimo objetivo de la tesis fue evaluar la eficacia de la inyecci&oacute;n de los desinfectantes en la red de riego para reducir la densidad de in&oacute;culo del hongo en el suelo y la VO bajo condiciones de ambiente natural en un experimento de larga duraci&oacute;n. Se combin&oacute; el cultivar Picual, un aislado defoliante altamente virulento de V. dahliae, y diferentes estrategias de aplicaci&oacute;n de OV (3,2 mL L-1) y OA (3,76 mL L-1) durante dos periodos comprendiendo desde final de invierno a final de verano. La desinfestaci&oacute;n redujo la densidad de in&oacute;culo total en el suelo (51,2% de media) y la incidencia de enfermedad e infecci&oacute;n (20,0% y 18,4% de media, respectivamente). La aplicaci&oacute;n quincenal de OA fue la estrategia que arroj&oacute; mejores resultados en t&eacute;rminos de reducci&oacute;n de in&oacute;culo total (75%) y esclerocios (85,4%) en el suelo, y reducci&oacute;n de s&iacute;ntomas (53%) e infecci&oacute;n (70,8%) en olivo. La desinfestaci&oacute;n, especialmente bajo la estrategia anterior, atenu&oacute; el impacto negativo de la infecci&oacute;n sobre el crecimiento y la producci&oacute;n al promover la recuperaci&oacute;n de la enfermedad. Los desinfectantes testados no solo reducen los esclerocios en el agua sino tambi&eacute;n al hongo en suelo infestado y la VO a ciertas concentraciones. Su uso se postula como una pr&aacute;ctica complementaria dentro del manejo integrado de la VO en Andaluc&iacute;a, en olivares y viveros que usen agua infestada por el pat&oacute;geno y en aquellos en los que el hongo ya est&eacute; establecido en el suelo. Los fabricantes de formulados deber&iacute;an considerar el desarrollo de productos conteniendo per&oacute;xido de hidr&oacute;geno para aplicar al agua.