Fusarium is a genus of common soil-borne fungi. While there are many different pathogenic fusarium species, some of the most damaging diseases are caused by strains of one species complex, Fusarium oxysporum.
They cause vascular wilt diseases by entering the roots and colonising the water-conducting tissue (xylem). This causes older leaves to yellow and plants to eventually wilt and die.
For more information check out these Soil Wealth ICP resources including a fact sheet on fusarium diseases and a webinar recording with plant pathologist Dr Len Tesoriero to learn the latest techniques in managing fusarium wilt in vegetable crops: