MaizeGuard AI

Disease Library

Reference guide for the 4 maize diseases detected by MaizeGuard AI

Northern Leaf Blight (MB)

Exserohilum turcicum

Northern Leaf Blight symptoms on maize

Symptoms

Long elliptical gray-green lesions on leaves, 2.5–15 cm, starting from lower leaves. Lesions may coalesce and cause extensive leaf death in severe cases.

Yield Impact

30–50% yield loss

Common In

Warm, humid environments. Prevalent in East Africa, including South Sudan.

Prevention

  • •Plant resistant maize varieties
  • •Practice 2-year crop rotation away from maize
  • •Apply foliar fungicides at early signs of infection

Common Rust (MR)

Puccinia sorghi

Common Rust symptoms on maize

Symptoms

Small circular reddish-brown pustules on both leaf surfaces. Pustules rupture to release powdery spores. Heavily infected leaves may turn yellow and die prematurely.

Yield Impact

20–40% yield loss in severe cases

Common In

Cool, humid climates. Can appear at any growth stage but most damaging during flowering.

Prevention

  • •Plant resistant hybrids adapted to your region
  • •Apply fungicide early if pustules appear before tasseling
  • •Avoid late planting which extends exposure to cool, wet conditions

Grey Leaf Spot (MG)

Cercospora zeae-maydis

Grey Leaf Spot symptoms on maize

Symptoms

Rectangular gray to tan lesions parallel to leaf veins. Lesions are sharply defined and uniform in width. Can cause rapid leaf death in favorable conditions.

Yield Impact

Up to 70% yield loss in epidemic years

Common In

Prolonged high humidity and overcast skies. Worsened by conservation tillage leaving crop residue.

Prevention

  • •Rotate crops — avoid planting maize after maize
  • •Reduce crop residue through tillage where feasible
  • •Select tolerant or resistant maize varieties

Common Smut (MS)

Ustilago maydis

Common Smut symptoms on maize

Symptoms

Gall-like tumors (swellings) on ears, tassels, stalks, and leaves. Galls are initially covered by a silvery membrane that ruptures to release dark spores.

Yield Impact

10–20% yield loss typically

Common In

Dry conditions with sporadic rainfall. More common when plants are wounded by hail, insects, or cultivation.

Prevention

  • •Remove and destroy galls before they rupture
  • •Avoid mechanical injury during cultivation
  • •Maintain balanced soil fertility — excess nitrogen increases susceptibility