Abstract:
The special race of the stem and bulb nematode Ditylenchus dipsaci, which attacks and propagates in tulips was found for the first time in Denmark in the autumn of 1975. Careful examinations carried out since then have shown that infestations occurred in two nurseries only.
Strict voluntary precautions combined with chemical control have now almost eradicated the nematodes.
As tulips are easily damaged by hot water treatment, experiments with nematicides were carried out with oxamyl ("Vydate L") 25%, aldicarb ("Temik 10 G") 10% and carbofuran ("Furadan 5 G") 5%. Bulbs were treated with oxamyl by dipping in 0.2% and 0.4% active ingredients for half an hour.
Both concentrations had a satisfactory effect on the nematodes.
Prolongation of the treatment to two and four hours caused only a small increase in the effect.
Aldicarb 10% and carbofuran 5% were placed in the furrow when bulbs were planted.
Aldicarb was applied at the rate of 0.1 g and 0.2 g active ingredients per metre of the row.
A good effect on the nematodes was obtained with 0.2 g, while 0.1 g proved to be insufficient.
Carbofuran was applied at the rate of 0.075 g and 0.15 g active ingredients per metre of the row; however, both of the doses affected the nematodes only slightly.
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