Streak disease of maize is caused by

Maize streak disease is caused by the Maize streak virus (MSV), a member of the genus Mastrevirus in the family Geminiviridae. It is one of the most economically important diseases of maize in sub-Saharan Africa.

The disease is transmitted by leafhoppers, particularly Cicadulina mbila. Infected plants develop characteristic pale yellow to white streaks running along the leaf veins, which give the disease its name. Severe infections can stunt growth and drastically reduce grain yield.

The causal agent is a virus, not a fungus, bacterium, or nematode. Fungal diseases of maize include maize smut (caused by Ustilago maydis) and downy mildew. Bacterial diseases include bacterial leaf blight and Stewart's wilt. Nematodes cause root damage but are not associated with streak symptoms on leaves. The distinctive yellow streaking pattern on maize leaves is a reliable field indicator of viral infection by MSV.