Witches' broom disease of Lime in Sultanate·of Oman
Dr. Bové, of INRA Bordeaux (Fr), has reported to us the appearance of a new witches' broom disease on lime (Citrus aurantifolia) in the Sultanate of Oman.
Thousands of trees have been killed. Infection starts with the appearance of one witches' broom, with leaves much reduced in size. Many others follow, until the whole tree is covered, with practically no normal leaves and shoots remaining on the tree. Fruit production is reduced to zero. Numerous mycoplasma-like organisms (MLOs) have been found in sieve-tubes of affected trees. It seems likely that the disease is transmitted by an insect vector (psylla or leafhopper), but this is not yet proved.
Since lime is the main citrus species cultivated in Oman, it is not yet known whether the MLO presents a danger to other citrus. Thus the danger to the citrus species widely cultivated in EPPO's Mediterranean members is not yet completely clear. Nevertheless, it seems prudent to consider this disease as a quarantine risk potentially as great as citrus greening bacterium, now present in other parts of the Arabian Peninsula. The EPPO working Party on Phytosanitary Regulations is making a further study of the risk presented to EPPO.
J. Bové, Bordeaux (FR).