Many pathogens are capable of causing more or less extensive spots and deterioration on melon leaves. They are sometimes quite comparable to those caused by various non-parasitic diseases. The risks of diagnostic confusion are therefore quite significant. In order to facilitate your identification, we advise you to adopt the following procedure:

- observe spots on several leaves and various plants in order to try to assess their nature exact and evolution over time (size, coloring, presence or not of a halo, location on the plant and distribution on the leaves ...) (see figures 1 and 2);

 

- always look carefully at the upper and lower surfaces of the leaves in order to note the possible presence of "fruiting bodies" of a fungus or other "signs" and elements facilitating the diagnosis;
- be aware that the size of the spots is likely to change over time, influenced in particular by the ambient humidity when they are caused by fungi or phytopathogenic bacteria. Thus, during particularly humid conditions, their extension may be abnormally large. Otherwise, following dry periods, they will have a more limited development than usual, which may lead you to choose an incorrect section.