Several viruses affect Narcissus (daffodil), the most common is Narcissus yellow stripe virus. This causes yellow streaks down the leaves of daffodils, lack of vigour and leaf and stem distortion.
What are daffodil viruses?
Infections by Narcissus yellow stripe virus and other viruses usually do not kill plants, but cause a loss of vigour and a wide variety of discolourations and distortions. This is most commonly seen when the foliage is growing in spring and early summer.
Narcissus yellow stripe virus infects daffodils and jonquils. Other common viruses are Narcissus white streak virus (limited to N. tazetta types), and Cucumber mosaic virus, which usually goes undetected, but causes lack of vigour.
You may see the following symptoms:
- The most common, Narcissus yellow stripe virus, causes yellow streaks down the leaves of daffodils and jonquils. These become progressively more pronounced as the leaves lengthen
Other symptoms of this and other viruses include:
- Lack of vigour
- Flower ‘breaking’ (white flecks and streaks) – not to be confused with bicoloured flowers
- White, coalescing streaks on the leaves
- Distorted stems and leaves
- Gardeners should minimise the risk of virus infection in daffodils and other Narcissus species by seeking virus-free stock. Plants with suspicious symptoms should be destroyed, there are no cures for plant viruses
- Planting on fresh sites where Narcissus have not been grown previously will slightly reduce the risk of nematode-transmitted viruses, although nematodes have very wide host ranges
- New varieties are less likely to be affected than old ones
There are no chemical controls. The use of insecticides to reduce aphid transmission is not practical.
Plant viruses share many of the characteristics of those that infect animals, though they do not cross infect (plant viruses only infect plants). Viruses are extremely minute and consist of a protein coat and a core of nucleic acid. They have no means of self-dispersal, but rely on various vectors to transmit them from infected to healthy plants. Once viruses penetrate into the plant cells they take over the cells’ nucleic acid and protein synthesis systems and ‘hijack’ them to produce more virus. They then require another vector to feed on the infected tissue and carry them to a new host.
Aphids are the vectors of Narcissus yellow stripe virus and several other viruses. Aphids do not breed on daffodils, but winged forms do visit and feed and can therefore transmit viruses. Narcissus species are also affected by several viruses which are vectored by plant parasitic nematodes (eelworms) which live in the soil. One of the more important is Arabis mosaic virus, but this is hard to detect without specialist techniques because the symptom is simply a lack of vigour.
Some viruses can be transmitted via seed, but generally these are a minority and therefore seed propagation is a useful way to minimise infection levels. Where plants are propagated vegetatively year after year, as are the older Narcissus varieties, there is a much greater risk of virus infection levels building up. Where cross pollination techniques have been used to breed new varieties, these are less likely to be affected.
Common name Daffodil viruses
Scientific name Narcissus yellow stripe virus and others
Plants affected Narcissus (daffodils)
Main symptoms Yellow streaked leaves, lack of vigour, leaf and stem distortion
Caused by Viruses