What is Sumatra Disease of Cloves?
Sumatra disease is caused by the bacterium Ralstonia syzygii. Its only host is the clove tree (Syzygium aromaticum). It tends to affect older, larger trees that are at least ten years old and 28 feet (8.5 m.) tall. Early symptoms of the disease include leaf and twig dieback, usually starting with older growth. The dead leaves may drop from the tree, or they may lose their color and remain in place, giving the tree a burnt or shriveled appearance. Affected stems may also drop, making the overall shape of the tree jagged or uneven. Sometimes this dieback affects only one side of the tree. The roots may start to decay, and gray to brown streaks may appear on newer stems. Eventually, the whole tree will die. This tends to take between 6 months and 3 years to happen.
Combatting Sumatra Clove Disease
What can be done to treat cloves with sumatra disease? Some studies have shown that inoculating clove trees with antibiotics before symptoms start to show can have a positive effect, slowing down the appearance of symptoms and extending the productive life of the trees. This does, however, cause some leaf burn and stunting of flower buds. Unfortunately, the application of antibiotics does not cure the disease. As the bacterium is spread by the insect Hindola spp., insecticidal control may help prevent the spread of the disease. The bacterium spreads easily with very few insect vectors, however, so insecticide is not by any means a completely effective solution.
