Stages of leaf spot disease
Stage 1 (speck/dot)
Yellowish green specks less than 1 mm long.
Stage 2a (early streak)
Specks become 3 to 4 mm x 1 mm long streaks, increase in length and turn yellowish.
Stage 2b (late streak)
Streaks darken to a rusty brown.
Stage 3 (early spot)
Streaks broaden to a spot. They become longer and wider, with indefinite margins, which may be water-soaked in appearance and darken to brown.
Stage 4 (Brown spot)
Spots have definite dark brown edges, the centre becomes sunken and is sometimes surrounded with a yellow halo. Conidia are produced on the surface.
Stage 5 (mature spot)
The sunken centre of spots turns grey and is surrounded by a dark brown to black border, sometimes with a yellow halo. Ascospores are produced within the grey central area of the mature spots.