Tikka Disease of Groundnut Overview

Study Notes

Tikka disease, also known as leaf spot disease, is caused by two species of Cercospora: Cercospora arachidicola and Cercospora personata.
It affects groundnut crops in many countries, including the US, China, and India.
The disease can reduce crop yields by approximately 22%.
Cercospora arachidicola causes early leaf spot, characterized by small, brown spots with yellow halos.
Cercospora personata causes late leaf spot, characterized by numerous, larger, black spots which are more damaging.

The disease is widespread in tropical regions with significant groundnut production.

Mycelium:
- C. arachidicola mycelium is dark brown and intracellular (grows inside plant cells).
- C. personata mycelium is brown/black, initially intercellular (between cells), then intracellular.
Haustoria:
- C. arachidicola lacks haustoria.
- C. personata has branched haustoria.
Conidiophore:
- C. arachidicola conidiophores are yellowish-brown, geniculated (bent), and septate (divided by cross-walls). They are 22–44 μm long and 3–5 μm wide.
- C. personata conidiophores are light brown, geniculated, and aseptate (no cross-walls). They are 25–54 μm long and 5–8 μm wide.
Conidia:
- C. arachidicola conidia are hyaline (pale yellow), cylindrical, and septate (with 1–12 septa). They are 38–108 μm long and 6–8 μm wide. The shape is truncate at the base and subtruncate at the apex.
- C. personata conidia are short, cylindrical, septate (3–4 septa), rounded at one end and tapered at the other. They are 18–60 μm long and 6–11 μm wide.

Early leaf spot (C. arachidicola): Brown or oval spots with yellow halos.
Late leaf spot (C. personata): Large, dark, black spots on leaves, stems, seeds, and shells.

Early infection management methods include:
- Crop rotation
- Eradication of infected plants
- Pruning infected parts
- Seed treatment with sulfuric acid or copper sulfate solution
- Seed dressing with Agrosan GN
Late infection management relies on fungicides, like Bordeaux mixture.

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