Leaf scorch is a fungal disease of Narcissus, caused by Didymella curtisii (syn. Stagonospora curtisii). It is favoured by wet weather, and is most common in the mild, wet climate of south-west England. It may be found in other parts of the country in wet summers.

In addition to narcissus, the leaf scorch fungus has been recorded on a number of other plants in the family Amaryllidaceae, including Amaryllis, Crinum, Galanthus, Hippeastrum, Nerine, Sprekelia and Sternbergia.

You may see the following symptoms:

• Leaf tips take on a red-brown, scorched appearance soon after emergence. This can be mistaken for frost damage
• The scorch symptom spreads down the leaf, and similarly-coloured spots appear at other points on the leaf
• Fungal fruiting bodies may be visible as tiny black dots within the affected leaf tissue
• Affected leaves turn yellow, then brown, and shrivel and die. Even on completely shrivelled leaves the red-brown spots are often still visible
• Brown spots and blotches may affect the flower stalk and flowers

Non-chemical control

• Whilst many narcissus species and cultivars can be affected when weather conditions are favourable for the disease, it is often worst on Poeticus, Polyanthus, Poetaz and Tazetta types. It would be prudent to avoid these types where the disease is a recurring problem
• Storage of bulbs at low temperature sometimes increases the problem, especially if combined with late planting
• Picking off and destroying affected leaf tips as soon as they appear will check the spread of the disease
• Severely affected plants are best removed and disposed of
• Dispose of all leaf debris where the disease has occurred

Chemical control

There are no fungicides available to gardeners for use against narcissus leaf scorch.

The fungus can survive between the scales of the bulb, particularly in the neck region, and infects the new leaves as they emerge in spring. It does not usually cause decay in narcissus bulbs, although bulb rotting has been recorded on some of the other hosts. The fungus can also survive on old leaf debris.

Microscopic spores produced in the fruiting bodies on affected aerial parts of the plant are splashed by rain droplets and can lead to further spread of the disease, both on the affected plant and on to neighbouring plants. The disease develops most rapidly at temperatures of 15-20°C, but can be active down to 5°C.

On Hippeastrum, the fungus causes a disease known as red spot. Bright red spots develop on the bulb, and the affected areas become sunken and soft as they enlarge. Red spots and streaks also develop on the leaves and flower stalks.