Symptoms
- Bulbs after lifting or, more often, while in store develop a brown discoloration and softening of the basal plate. The rot spreads through the inner bulb scales, which turn reddish-brown. A pinkish white fungus is often visible on affected tissue. Eventually bulbs become brittle, shrunken and mummified.
- Narcissus growing in grass or in borders fail flower.
- If infection is slight foliage is sparse, yellowed and stunted.
Cause
This is one of the most serious diseases affecting narcissus.
It occurs in many soils, even occasionally those where narcissus are not known to have been grown previously. The fungus infects bulbs either from the soil, either via the
roots, through the base of the bulb or through small wounds,
made usually when the bulbs are lifted. Basal rot develops most rapidly in
bulbs stored at temperatures higher than 22oC (72oF). Below these temperatures the disease can still progress, but more slowly, so that severe symptoms are not present by the time the bulbs are replanted. It is these lightly infected bulbs that are a main cause of the disease being introduced to new sites.
The disease is carried over from one season to the next through the bulbs. Where narcissus are not lifted, infected bulbs will rot away. The disease is likely to spread gradually to adjacent bulbs, so that after several seasons large gaps may appear in a group of naturalised plants.
Prevention
- If basal rot is a problem, lift daffodil bulbs early, six weeks after flowering (before the soil warms up).
- Handle bulbs with care to avoid bruising.
- Do not expose bulbs to hot sunshine.
- Before storing dust bulbs with sulphur (Vitax Green Sulphur or Yellow Sulphur).
- Keep bulbs in cool, airy conditions.
- Plant early in autumn.
- Check bulbs before planting, and discard any that are not firm and healthy.
- If the disease is suspected in naturalised narcissus lift and check bulbs.
Control
There is no cure for this disease. Infected bulbs should be destroyed by burning or put in a sealed bag in the dustbin. Do not compost infected material.