Fusarium

Fusarium is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants.

A mould of a large genus which includes a number that cause plant diseases, especially wilting.
The symptom of fusarium is where the leaves on infected plants turn yellow and fall.
The plant wilts over several days and then dies.

A typical symptom of fusarium wilt is the reddish-brown discolouration of the water conducting tissue of the stem and roots, seen when these parts are cut with a sharp object.