THE CONTROL OF FUSARIUM WILT ON CARNATION WITH A STREPTOMYCES PREPARATION

Carnation wilt disease caused by Fusarium oxysporum Schl. f.sp. dianthi (Prill. & Del.) Sn. & Hans. is the most serious disease of the carnation crop causing considerable economic losses. Chemical fungicides used so far have not been effective enough. Promising results have been obtained with Streptomyces microbe isolated from Finnish light-coloured Sphagnum peat known for its disease suppressing effect. A great number of Streptomyces strains were studied for their antagonistic effect first on nutrient medium, later on in pot experiments and also in greenhouse trials on a practical scale. Streptomyces isolates used as biological control agents were identified as S. griseoviridis Anderson et al. Initially a laboratory preparation was applied, but later on Kemira Oy developed a commercial powdery product, under the trade name of Mycostop, containing mycelium and spores of this microbe.

The effect of Streptomyces preparation against Fusarium wilt on carnation was tested both in artificially and naturally infected experiments. The disease control was carried out by dipping the roots of the cuttings in microbe suspension and spraying the peat surface with it after planting and repeating the spray treatment 2 – 3 times during the growing season. These applications prevented the spreading of the disease and increased the yields of carnation. In commercial greenhouse cultivations the wilt of carnation was controlled so effectively that the percentage of severely diseased area decreased to 10 % compared to 30 – 45 % on untreated plants.