Application to soil of disinfectants through irrigation reduces Verticillium dahliae in the soil and verticillium wilt of olive

Abstract

The application of disinfectants through drip irrigation could be a feasible practice against verticillium wilt (Verticillium dahliae) of olive. OX‐VIRIN (activated peroxide) and OX‐AGUA AL25 (quaternary ammonium compounds) are two disinfectants that have shown efficacy against V. dahliae in irrigation water and potential for reducing the disease in young olive plants. In this work, various post‐planting application strategies incorporating OX‐VIRIN (once a month, or twice a month on alternate or successive weeks) or OX‐AGUA AL25 (once a month, or twice a month on alternate weeks) were assessed for their effect on V. dahliae in soil, disease in olive trees, and olive yield, in a 2‐year pot‐experiment under natural environmental conditions. The disinfectants were injected via metering pumps into a drip irrigation system that irrigated olive trees planted in V. dahliae‐inoculated soil. All the application strategies significantly reduced the total inoculum density in soil compared to controls with no disinfectants and noninoculated soil. The microsclerotia density was also significantly reduced in disinfested soils by 73.6–86.8%, depending on the strategy. The symptoms and infection incidence were always lower in treatments subjected to disinfestation. The treatment with OX‐AGUA AL25 applied twice a month on alternate weeks most reduced the symptoms (by 53.0%) and colonization index (by 70.8%) with respect to untreated water control. This soil disinfestation also significantly strengthened the symptom remission. Tree growth and production were negatively affected by soil inoculation (reduced by 45.6% and 88.7%, respectively), but not so by disinfectants, which even relieved the reduction in inoculated soils, especially when OX‐AGUA AL25 was applied.