Many viruses affect Lathyrus spp. (sweet peas) causing streaked flowers, mottled leaves, stunted growth and dead patches on leaves.
What are sweet pea viruses?
There are about 57 viruses worldwide that affect sweet peas, including many that affect peas, beans, clover and alfalfa (lucerne) as well.
In reality only four are of major importance to gardeners in the UK. These are:
- Pea enation mosaic virus (PEMV)
- Bean yellow mosaic virus (BYMB)
- Pea mosaic virus (PMV)
- White clover mosaic virus (WCMV)
Symptoms may be seen when the plants are growing from spring until late summer.
You may see the following symptoms:
- Mottled and white-streaked leaves
- Dead spots or patches on leaves
- Colourless veins
- Translucent patches on leaves
- ‘Breaks’ (white streaks) on flower petals
- Stunting and loss of vigour
Note that some of these symptoms are similar to those of nutrient deficiencies, but these are unlikely to occur if a balanced fertiliser is used.
- If infection is suspected, remove infected plants and destroy, there are no treatments for virus infection
- Consider buying good quality seed, rather than plants, as most viruses are not seed borne
- Remove legume weeds such as clover which may harbour viruses
- Clean pruning tools with garden disinfectant between plants
- Sweet peas, particularly cordon grown ones, are subject to virus-like symptoms, so check that growing conditions are being met
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.
The VIDE (Virus Identification Data Exchange) database lists 57 viruses worldwide that are capable of infecting sweet peas with at least 11, and probably more, of which occur in the UK. A large number were first recorded from related crop legumes such as peas, beans, clover and alfalfa.
Many viruses have aphids as vectors (disease-carriers) but some are transmitted by mechanical means (for examples on tools or by handling) and a few are transmitted by soil-dwelling nematodes (eelworms). Some can be transmitted through seed to the next generation but the majority are not.
Common name Sweet pea viruses
Scientific name Various
Plants affected Lathyrus spp. (sweet peas)
Main symptoms Streaked flowers, mottled leaves and stunted growth
Caused by Viruses
Timing Spring until late summer