An accurate and reliable diagnosis depends largely on the sample received. When possible, deliver an entire plant with its substrate (minimum 1 litre). Even if symptoms of wilting or necrosis appear only on leaves, branches or fruits, still provide the entire plant and its substrate. Such symptoms can be caused either by an infection of the stem or roots, or by an inappropriate substrate.
Provide a large enough quantity of infected material that represents the damage. Avoid sending completely dead plants/plant parts because many other organisms become active in dead plant tissue. Their presence hinders isolation of the primary pathogen.
If the presence of the pathogen is obvious on the leaves (insects, fluffy mold, etc.) fresh leaf samples suffice.
The pathogen is usually located at the transition zone between sick and healthy tissue. If only a part of the plant can be sampled, such as for trees or larger bushes, the transition zone between sick and healthy tissue must be present in the sample.
Healthy material, sent in a separate container, can be helpful as a comparison.
A description of the situation can also help. Note any plant protection products applied, herbicides used, crop rotations, situation in which the plant was grown, etc. Pictures are also helpful.
Download the information sheet (pdf) and fill it in as completely as possible.