Petiole and Leaf Sheath Streaking, Mottling and Morse Code Symptoms
  • BBTD is diagnosed by identifying symptoms of diseased plants or by submitting a banana leaf sample for virus testing
  • The mottling symptom on the banana petioles and leaf sheaths resembles the Morse code symptom and the mottling on the leaves and flowers, the set of "dots and dashes" visible along the main veins of banana tissues and organs
  • To best view this symptom, you may have to rub away the white, powdery and waxy layer of cells covering the banana petiole or leaf sheath.

When infected with Banana Bunchy Top Virus (BBTV), the veins on diseased banana petioles and leaf sheaths develop a green mottling and green streaking symptom which resembles the "Morse code" symptom associated with diseased leaves.

This symptom is a reliable indicator of bunchy top disease. Sometimes, the waxy layer of cells of the surface of the petiole must be rubbed away in order to see the symptom distinctly.

Note the dark green, discontinous streaking on the petioles and leaf sheaths in these five photographs of banana plants with bunchy top disease.


The streaks are partially obscured by the powdery white layer of cells which cover the banana petiole.

Streaking may appear as very dark lines or dashes running parallel to each other.

The streaks are partially obscured by the powdery white layer of cells which cover the banana petiole.
Streaking may appear as very dark lines or dashes running parallel to each other.

Photographs are courtesy of the University of Hawaii and the Hawaii Department of Agriculture


Maintained by Scot Nelson: snelson@hawaii.edu
Last Revised on September 12, 2006