Potential efficacy of soil-applied disinfectant treatments against Verticillium wilt of olive

Disinfestation of irrigation water has re-emerged the interest in including disinfectant treatments within the integrated management of Verticillium wilt of olive to reduce the pathogen spread and introduction through irrigation facilities. OX-VIRIN® (OV) and OX-AGUA AL25® (OA) are two disinfectants based on oxidizing and non-oxidizing agents, respectively, that have shown a potential efficacy reducing water infestations by V. dahliae under certain guidelines. This investigation was designed to evaluate now their effects on V. dahliae in the soil, the olive plant and the plant-pathogen interaction under growth chamber conditions. Seven disinfectant treatments were applied through watering to V. dahliae-infested soils sustaining 'Picual' or 'Arbequina' olives. The OV-w (weekly), OV-m (monthly) or OA-b (biweekly) treatments reported a significant deleterious effect in the total inoculum density in soil and reduced or tended to decrease the sclerotia survival of all V. dahliae isolates (three isolates used) in presence of both cultivars in all the experiments (two experiments per cultivar were carried out). 'Picual' olives exhibited a greater disease incidence than 'Arbequina' ones. The incidence of diseased plants was lower in olives subjected to disinfectant treatments in comparison with those under untreated control, with a maximum reduction of 21.1% and 43.4% in 'Picual' and 'Arbequina', respectively. OV-w or OA-b treatments applied to 'Picual' and OV-w treatment to 'Arbequina' decreased partially but solidly (all experiments per cultivar) the disease intensity index. Furthermore, values from the area under the disease progress curve were significantly reduced by OV-m and OA-b treatment in both 'Picual' experiments, depending on the isolate. The olive growth parameters were not significantly affected by the disinfectants and an absence of phytotoxicity was reported. Results from this work demonstrate that disinfection treatments reducing the fungus in water can also potentially reduce the fungus in soil and, partially, the Verticillium wilt in olive.