Título en español.

Studies were undertaken to determine the cause of the so called witches' broom disease of pigeon pea in Puerto Rico. Typical witches' broom occurs when -leafhoppers of the Empoasca fabae complex colonize (in numbers) on field plants. The disease can be reproduced under controlled conditions and can be eliminated by suppression of the insects. Mycoplasma-like organisms were found to be associated with a bushy canopy disease of the pigeon pea plant. This condition should not be confused with the typical witches' broom. No rhabdovirus particles were found in association with the bushy canopy or typical witches' broom diseases. Electron microscopy of tissues from pigeon pea plants with a pale mosaic revealed the presence of rhabdovirus particles. No mycoplasma-like organisms have been found so far in tissues affected by the pale mosaic. No mixed infections were detected in the present studies.