Yellow sigatoka leaf spot (Mycosphaerella, banana leaf spot)
The earliest symptom is a light-green, narrow speck about 1 mm in length on the upper surface of the leaf. The speck develops into a streak several millimetres long and 1 mm or less in width running parallel to the leaf veins. The streak elongates and expands laterally to become elliptical in shape and turns rusty red. A water-soaked halo forms around the lesion when the leaf is turgid. This is best seen in the early morning when dew is present on the leaf. This infiltrated tissue quickly turns brown and a young spot is formed. The dark-brown centre of the spot later shrinks and appears sunken and the halo turns a darker brown. The sunken area becomes grey and the halo darker brown forming a well-defined ring around the mature spot, which remains distinct even after the leaf tissue has died. On leaves of young plants, individual spots tend to be larger and more spherical. Mature spots are normally 4-12 mm in length.