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Symptoms

Plant pathogens cause diseases with a range of different symptoms. These symptoms can be used to identify the pathogen and then treat the disease, or limit its effects.

Observation

Many plant diseases can be identified simply by looking at the plant. The symptoms of common plant infections are show in the table below.

Identification

Farmers and gardeners often use books and the internet to identify plant diseases. They can also take a small cutting of an infected plant (or a photograph of it) to a local garden centre, which have staff that can often help identify and treat the disease.

Laboratory tests

Observation alone is not always enough to diagnose a plant disease. For diseases that are more difficult to identify, cuttings of the plant may be analysed by scientists in laboratories.

Use of monoclonal antibodies

Monoclonal antibodies can recognise a specific antigen. Samples of the plant tissue can be tested with the monoclonal antibody. If the pathogen's antigens are present in the plant tissue then the monoclonal antibody sticks to it. Another antibody is then added which can bind to the monoclonal antibody. This antibody has a marker on it, such as a dye, which then signals to the scientists that the monoclonal antibody recognised an antigen.

Analysing DNA

Another option is to analyse the DNA in the plant. Samples of the diseased plant can be analysed in the laboratory by scientists. Each plant pathogen has its own unique DNA. The plant can be tested for this DNA.

If the pathogen's DNA is found in the plant tissue, this gives more evidence for that particular disease. This makes the disease easier to treat specifically, for example, using fungicides if it is found that a fungus has infected the plant.