Dealing With Plant Viruses
Just like people, plants can get viruses too – and viral diseases are probably the hardest of all garden problems to diagnose, and certainly the most difficult to control.
A range of different viruses affect garden plants – some being very specific and attacking only particular kinds of plant, while others pose more of a general threat. The names given to many viruses can also be a cause of some confusion; they tend to be named after the first plant they were found on, but this doesn’t always mean that they only affect it. Trees and shrubs for instance are generally quite resistant to viral attack, but cucumber viruses are amongst the few that cause them problems – which, of course, you would be very unlikely to suspect just from the name!
Virus SignsThe signs of viral infection are typically very varied, with all manner of growth problems distortions and discolouration being produced.
The leaves of affected plants, for instance, may be streaked with yellow or brown stripes, develop patches of odd colours, turn completely yellow/white or exhibit a mosaic effect of yellow blotches. Some viruses make the leaves crinkly or otherwise distorted, and the plants themselves may be killed or stunted – or they may show no other signs of ill health at all, while others produce crinkled leaves and yellow patches which look almost indistinguishable from the effects of leaf and bud mites.
Working out what the problem is can be an almost impossible task and often it is only knowing the kinds of virus that are most likely to infect a particular plant that gives any clue as to what is really behind the attack. Raspberries, for instance, are particularly prone to Mosaic virus, while a number of viruses including Crinkle virus, Yellow Edge and Arabis Mosaic affect strawberries at different times of the year. Tobacco mosaic virus can affect tomatoes and peppers, as can cucumber mosaic virus – as well as beetroot, celery, spinach and some varieties of trees and shrubs.
Dealing with the ProblemSince there is no cure for viruses, controlling them is all about avoiding infection in the first place and although this can never come with a 100 per cent guarantee of success, a few simple precautions can significantly tip the odds in your favour.
Viruses are carried from plant to plant in a number of ways, which means that if you can reduce the chance of this happening, you’ll also lessen the likelihood of infection.
Some viruses can be spread by other pests – especially sap sucking insects such as aphids. Control their numbers and you will make a huge impact on the potential virus problems associated with them.
Likewise hands and tools can also carry viruses, so being careful when you work in the garden and making sure that you don’t touch healthy plants directly after ill-looking ones can also make a big difference. Make sure you wash any pots or containers thoroughly and disinfect them before reusing them; recycling is a great thing, but don’t be too quick to recycle viruses too!
Selecting your stock wisely, both when buying new or taking cuttings, is also important; buying healthy new plants and avoiding propagating obviously infected ones – however treasured the parent stock may be – is another major factor in reducing viral problems. Wherever possible, look for plants that are certified virus-free or pick resistant strains to grow.
If you do come across any plants that are obviously suffering, hard as it may be, the only thing to do is to remove any infected material and burn it; although it may seem a drastic step, it’s the only way to avoid supporting a constant reservoir of disease.
Virus infections can be a serious problem for the gardener – there’s no point in pretending otherwise – and once they have managed to establish themselves, the battle is already as good as lost.
Dealing with plant viruses calls for vigilance, preventative measures, good garden hygiene and the ruthless destruction of any plants showing signs of infection. If you pick your plants wisely and take care of them along the way, with luck your virus problems will be small ones!