4 Causal Organisms

i. Early Blight of Potato:-

Pathogen:- Alternaria solani

ii. Downy Mildew of Grapes:-

Pathogen:- Plasmopara viticola

iii. Blast disease of Rice:-

Pathogen:- Pyricularia grisea (P. oryzae) 

iv. Red Rot of Sugarcane:-

Pathogen:- Glomerella tucumanensis. (Older name = Colletotrichum falcatum)