Dealing with diseases

This section will help you to recognize and combat common diseases.

Many diseases attack our crops, the effect this has can be devastating. You plant your seeds, nurture your seedlings, watch them grow into healthy little plants and you look forward to picking your produce. Then disaster strikes and all your hard work is lost. The scary part is that it can happen overnight.

The best ways to avoid this happening as always is vigilance and good husbandry. Check your plants as often as you can, get up close and personal with them (they won't mind!) Check leaves, stems and fruit for signs of attack, try to keep your greenhouse, polytunnel or garden clear of rotting vegetation. If crops are undercover try to provide good ventilation.

Sometimes there will be nothing you can do, the changing climate can trigger diseases that you may never have had before, all you can do is put it down to experience and try to learn from mistakes.

Listed below are some of the more common diseases and how to deal with them.


Blight is the common name for a number of different plant diseases, especially those that lead to sudden serious leaf damage. Some are caused by a microscopic fungus.

Cane Blight - affects Raspberries

Causes leaves to wilt and canes to become brittle and snap. Cut off canes at base and burn them.

Potato and Tomato Blight

Probably the worst enemy of the humble potato. The same disease effects both crops but is usually spread first by the potatoes or by infected tubers that have been left in the soil. The first signs of attack are brown patches on the tips of the leaves, eventually spreading to the stems and killing the plants. Warm wet weather is normally the trigger for blight. The spores are airborne and spread quickly, they also wash down into the soil and infect the potato tubers which end up rotten and foul smelling. Unfortunately, by the time you have spotted the signs it is usually too late for treatment.
Blight can be prevented provided you take action in time. Spray foliage including the underside with a fungicide (available from garden centres) repeat applications at 3 week intervals from mid-June/beginning July. If blight persists on your potatoes cut down foliage straight away and burn (do not compost) potatoes should be fine underground for up to 3 weeks.

This fungus also causes serious damage to tomatoes. Brown spots begin to appear on ripening fruit, when blight is spotted on potatoes, tomato plants should be sprayed also, spraying your tomatoes early will help protect the cop.


This is a disease all gardeners dread finding, it is a fungal disease which effects mainly Brassica crops but sometimes other root vegetables to. Once you have the disease it can stay in your soil for up to 20 years. Tell-tale signs are, wilting even when plants are well watered, dig up effected plants and have a look at the roots, these will be distorted and swollen, plants will eventually collapse.

There is no cure, if your crop is infected with club root dig up plants straight away and burn them to avoid the disease spreading. Avoid using the same patch of soil for brassica's in the future. Try to avoid the disease in the first place by practicing crop rotation and trying disease resistant varieties.


Grey mould is a fungi and attacks almost every plant and vegetable in the garden. It covers foliage and stems with a soft grey fluff and is more common when conditions are damp. When infected plants are disturbed, clouds of spores are released infecting everything in the surrounding area. It thrives on dead and rotting vegetation and spreads rapidly among weak plants often killing them.

To combat this problem, try not to overcrowd your plants, leave plenty of space between them, clear away any rotting matter and provide good ventilation. Try watering at the base of the plants rather than from overhead. Try to grow disease resistant varieties if possible.


This disease first appears as a brown softness at the neck of the onion bulb. It is a fungal disease made worse by wet weather and particularly effects stored onions. They become soft and develop a grey woolly growth. To help protect against this disease, add fertilizers such as potash to the soil, allow plenty of air circulation when growing and storing. Don't store damaged onions and practice good crop rotation.


Rust is easily recognizable by yellow/brown patches on the foliage of plants, giving a rust like appearance. There are many different types of this fungi which commonly affects leeks and beans, it is brought on by damp, warm conditions. Inspect plants regularly, pick off badly affected leaves and burn. Leave plenty of space between plants, provide good ventilation, water at base of plants if possible and try to keep the foliage dry.


This is a soil-bourne disease more common on heavy wet soils. It can affect many vegetables including beetroot, carrots, parsnips, swedes, turnips, asparagus, strawberries and potatoes. Infected roots, crowns and stems become covered in purple strands, It can stay dormant in the soil for many years. at first sign of attack lift and destroy infected plants.