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FUSARIUM CONTROL IN CARNATION USING REDUCED DOSAGES OF METHYL BROMIDE AND METHAM-SODIUM
Methyl bromide was applied as hot gas in two dosages: 70 g/m2 under low density polyethylene film (LDPE) and 35 g/m2 under an impermeable film (‘Barromid’). Metham-sodium was also applied in two dosages, 150 ml/m2 and 300 ml/m2, by sprinkling in sufficient water to wet the soil down to 60 cm depth.
The effectiveness of MB and MES on the control of F.o. dianthi was studied at soil depths of 0–60 cm, subdivided into three layers of 0–20, 20–40 and 40–60 cm, in three field experiments.
The efficacy of MB and MES control was also measured in terms of the viability of F.o. dianthi propagules placed in the soil at depths of 5, 20, 40 and 60 cm.
Disease incidence during the growth season of susceptible carnation cultivars was recorded too, as an additional parameter to determine the efficacy of the soil treatments.
In soil samples taken from the soil profile at the three depths, a few CFUs were recovered at all depths and in all dosages of MB and MES tested.
Methyl bromide and MES reduced the F.o. dianthi CFU counts at all soil depths between 0 and 60 cm in infested soil samples which were buried in the center of each plot, whereas 104 CFU/g soil were recovered in the untreated control plots.
In experiment 1, after the soil treatments, the plot was planted with the susceptible carnation cultivar ‘Citronella’. Disease incidence at 180 days after planting was 95, 36, 37, 37 and 28%, respectively, for the untreated control, the 150 and, 300 ml MES/m2, and the 70 and 35 g MB/m2 treatments, respectively.
Similar reductions of disease incidence were observed in the second experiment with the cultivar ‘Desio’. In an additional field trial, with MES treatments only, disease incidence in the cultivar ‘Hermon’ was 100% in the untreated control, 16% with 150 ml MES/m2 and 10% with 300 ml MES/m2.
Similar levels of control of fusarium wilt in carnations as well as F.o. dianthi CFU counts were achieved with the two fumigants.
Using impermeable film may reduce the MB dose by half from that usually applied, without affecting the efficacy of control.
With MES, 300 ml/m2 appears to be a high dose which could be reduced by half without influencing efficacy.