Effect of the irrigation dose on Verticillium wilt of olive

From autumn 2012 to autumn 2013 a survey comprising 70 olive orchards was carried out in an Irrigation Community of the central Guadalquivir Valley, (Andalucia, Southern Spain) with the objective of studying the influence of the irrigation dose on Verticillium wilt (Verticillium dahliae Kleb.) of olive (VWO). The 93.1% of the visited orchards were planted with susceptible cultivars to V. dahliae (`Picual' and `Flojiblanca'). Mean disease incidence (DI) of the orchards accounted for 14.9%. In almost all investigated plantations disease onset occurred after farmers had introduced irrigation. In the case that it was present, the introduction of the irrigation always encouraged VWO development, and DI was positively associated with the number of years of irrigation, showing a linear trend (P = 0.006). VWO was significantly more severe in olive plantations irrigated with high irrigation doses. The 47.1% of olive plantations were irrigated with mean values of 2059.9 (in 2012) and 1793.4 (in 2013) m(3)/ha, and showed the highest DI (21.42%). Plantations watered with lesser doses (the 28.6%) with average values of 712.5 (in 2012) and 741.5 (in 2013) m(3)/ha showed a DI significantly lower, which accounted for 13.3%. Finally, dry-land olive orchards (24.3%) showed the lowest DI (4.0%). (c) 2015 Elsevier B.V. All rights reserved.