Response of different intermediate-day onion hybrids to natural infestation by Phoma terrestris and Fusarium oxysporum f. sp. cepae in Ciudad Real, Spain with assessment of different soil disinfestation methods

Incidence and severity of Pink root caused by Phoma terrestris and Fusarium basal rot caused by Fusarium oxysporum f. sp. cepae were field-tested on factorial combinations of different soil fumigation treatments in five different intermediate-day onion hybrids widely adapted at the Bola?os de Calatrava area (Ciudad Real, Spain). The effect of Dazomet and virulence of the local isolates were then tested in trays under greenhouse conditions. When compared to Electric, the other four onion hybrids showed a certain degree of tolerance to Pink root and Fusarium basal rot with little difference among them. The field trial carried out in 2006 showed significant but negligible beneficial effects in medium bulb weight and Pink root severity due to Dazomet. The field trial carried out in 2007 showed significant beneficial effects of Metham-sodium on plant growth and Pink root and Fusarium basal rot severities. Sodium tetrathiocarbonate performed worse than the control. Greenhouse test showed that Dazomet performed nearly as well as sterilization under controlled conditions. Virulence of local isolates was lower than that of reference isolates.