Abstract

Attempts to transmit the disease from infected trees of Eucalyptus tereticornis (3 yr old) and E. grandis (5 yr old) by side and terminal grafts, or by growing dodder (Cuscuta chinensis and C. reflexa) on infected trees and then transferring it to healthy ones, were unsuccessful. Cuttings from diseased and healthy E. grandis failed to root in pots after hormone treatment, so transmission of the disease to cuttings could not be tested. TEM of sections from stems and petioles of diseased and healthy trees demonstrated the presence of pleomorphic mycoplasma-like organisms (MLOs) in the sieve elements of diseased phloem tissue, but not in healthy tissue. Tetracycline injection experiments in a 3- to 5-yr-old mixed plantation of E. grandis and E. eugenioides in Aug. 1983 gave a 60-90 day remission of symptoms 30 days after treatment. It is suggested that little leaf disease of eucalypts may be caused by MLOs