How to recognise it
The virus can show itself in a number of ways on different plants:
- On cucumbers and many other susceptible plants, an uneven mottling of the leaves is the first sign of infection, followed by the foliage twisting and curling. On cucumbers the fruit may show yellow sunken areas from the stem end.
- On the shrub Daphne odora, the foliage shows yellowing and mottling and the plant becomes more susceptible to frost damage, while on Euonymus spp. bright yellow leaf spots appear.
- On acquilegia the mottling can be accompanied by a clearing of the veins.
- Buddlejas in the later stages of the disease may show dwarfed and branched flower heads.
- On flowering herbaceous plants, such as campanula, the flowers can be crumpled and fail to open properly.
- Gladioli symptoms include white blotches on the flowers and a greyish leaf mottling.
- On lilies the symptoms are minimal (other than growth reduction) but when occurring alongside the ‘lily symptomless virus’ elongated flecks can develop on the leaves, at first yellowish but later grey or necrotic.
- Tomato plant leaves will reduce in size (known as the ‘fern-leaf’ symptom).
- Tulips display the symptoms of a corky fleck appearing as grey-brown sunken spots on the outer and inner bulb scales of later flowering varieties. Affected bulbs can give rise to deformed plants, sometimes with aborted or broken flowers and yellowish or necrotic leaf streaks.
The virus can also be latent, so a plant may have it and spread it to others without showing any symptons.
Why it’s a problem
Plants can become severely stunted, produce less fruit (in the case of cucumbers) and may eventually collapse altogether.
Where you are likely to find it
As well as cucumbers, this virus can affect a wide range of plants including anemones, aquilegias, asclepias, beans, begonias, buddlejas, cellistephus, campanulas, celery, cyclamen, dahlias, daphnes, delphiniums, euonymus, gladioli, hoyas, lettuce, lilies, loniceras, magnolias, marrows, matthiolas, narcissi, nicotianas, passifloras, pelargoniums, petunias, potatoes, primulas, spinach, stapelia, stephanotis, tomatoes, tulips, turnips, violas, zantedeschias and many common weeds.
How to prevent it
Ensure good hygiene as the virus can be spread on hands and implements. Most commonly it is introduced by aphids, so preventing an aphid infestation should also prevent this virus becoming established. It can also be transferred by fungi, so good fungal control is helpful.
Ensure that when propagating vegetatively (eg from pelargoniums) you only propagate from uninfected stock.
When growing susceptible plants ensure that their leaves aren’t touching, since this can transfer the virus from an infected to an uninfected plant.
Purchase certified plants, which will have been heat treated to kill any viral infections.
Remove unwanted plants (ie weeds) which may contract the virus and then pass it to other plants, these include chickweed, fat hen, common mallow, common bryony and teasel.
How to get rid of it
There is no cure for this virus. Remove and destroy infected plants and weeds (do not compost them on domestic compost heaps; instead you can put them in municipal green waste or burn them).
Is it good for anything?!
Other useful information
Viruses generally don’t infect the seed, so if a particularly precious plant is infected you can save the seeds before destroying the plant and they should grow into healthy new plants.