Fusarium is a vast worldwide genus of imperfect fungi that is of particular importance due to the fact that many species cause serious plant diseases. Fusarium categorization has always been based only on morphology. However, this categorization system has been a source of contention for many years. Because of morphological flexibility and a general lack of morphological features, classification of certain Fusarium species has been problematic, resulting in species composed of strains with dramatically varied physiological characteristics, such as host-plant specialization. All known Fusarium teleomorphs belong to the division ascomycota, however they are divided into many genera viz., Gibberella and Nectria. Fusarium conidium (macroconidium) is fusiform, multi-celled by transverse septa, with a foot-shaped basal cell and a pointed to whip-like apical cell. Furthermore, certain species may produce small conidia (microconidia). These are typically single celled, but can be three to five celled in some circumstances, and can be globose, oval, reniform, or fusiform. A few species generate microconidia in chains, whereas others grow them in slimy heads or singly. Fusarium wilt pathogens persist/survive as chlamydospores in soil for long periods.