Soil Chemical Treatments for the Control of Fusarium Wilt of Carnation in Spain

To study the effectiveness of soil chemical disinfestation treatments in the control of Fusarium wilt of carnation (FWC), two experiments were carried out during 2006-08 and 2008-09, respectively, in a naturally infested greenhouse planted with susceptible carnation 'Master'. Na-azide (65 ml m(-2)), 1,3-dichloropropene (1,3-D)+chloropicrin (CP) (40+10 ml m(-2)), and dimethyl disulphide DMDS+CP (30+10 ml m(-2)) were applied in early August 2006 (Experiment 1). In early July 2008 (Experiment 2) the two former treatments and DMDS, combined or not with soil solarisation (SS), respectively at the rates of 53 and 80 ml m(-2), were tested. An untreated control was included in both experiments. In Exp. 1, viability of F. oxysporum f.sp. dianthi (Fod) was nil at 30 cm depth in plots treated with DMDS+CP and low residual viability was observed at 15 cm depth, while it was much reduced with 1,3-D+CP at both depths. In Exp. 2, both fumigants eradicated Fod at 15 cm depth, except DMDS applied without SS. In Exp. 1, FW incidence of dead plants reached 100% in the control plots after 13 months from planting whereas in the other treatments it was under 18%. At the end of this experiment, 7 months later, FWC incidence ranged 14-44% for 1,3-D+CP and Na-azide, respectively. Nine months were required in Exp. 2 for control plots to reach 90% FWC incidence, whereas it was 44% in Na-azide-treated plots and the rest of treatments were under 9%. This suggests a consistency in the efficacy of 1,3-D+CP and DMDS. Total yields (number of stems m(-2)) in experiment 1 were increased to 412% that of the control in 1,3-D+CP treated plots, 248% for Na-azide and 371% in the case of DMDS+CP treatment; yields in experiment 2 were 292% and 236% for the first two, and 283% for DMDS (53 ml m(-2)) + SS whereas, in DMDS (80 ml m(-2)), 333% that of the control was reached. DMDS and 1,3-D+CP treated plots showed a significantly lower percentage of the lower commercial quality stems than the control, thus improving qualitative yield.