Image by U.S. Department of Agriculture
By Kristi Waterworth
An orange or lime tree can provide an amazing perfume for nights on the patio and fruits for drinks while entertaining, but if your tree was sick, would you know how to spot citrus greening disease symptoms? This disease is a serious problem across all citrus-producing states, causing infected citrus trees to develop symptoms mimicking nutritional deficiencies and inedible fruit that retains some of its green coloration.
What is Citrus Greening Disease?
Plants affected by citrus greening disease, also known as huanglongbing or yellow dragon disease, have acquired a serious bacterial infection. Citrus greening disease symptoms vary widely, but include new leaves that emerge small with yellow mottling or blotching, yellow shoots, enlarged, corky leaf veins, as well as fruits that are small, with green ends and filled with small, dark aborted seeds and bitter juice.
This bacterium is transmitted by the Asian citrus psyllid, a tiny, wedge-shaped insect with brown and white mottled coloration. Although small, this pest has citrus growers across America fearful for the future of the entire industry. If you see it in your backyard citrus trees, you should capture the bug and call your local extension service right away.
Control of Citrus Greening
There is no cure for citrus greening, which is why spotting citrus greening disease symptoms early is so crucial – rapid removal of infected trees is the only way to stop the spread of the bacteria responsible. Since infected trees will never again produce useful fruits, they only serve as a reservoir for this economically dangerous disease.
Plants affected by citrus greening include all the common citrus fruit trees, like oranges, limes and lemons, as well as ornamentals like orange jasmine, jackfruit and limeberry. Orange jasmine has been implicated in Florida as a means of transportation between nurseries for Asian citrus psyllids, since it is a favorite of this pest.
You may be able to prevent citrus greening by erecting a screen house around known, disease-free citrus trees, but psyllids are small, often no more than 1/8 inch long, so your screen must be tightly woven. Insecticides can be highly toxic to the bees that pollinate citrus, but if you live in one of the many citrus greening quarantine zones, it may be useful to treat your citrus tree’s leaves with chlorantraniliprole, spinetoram, dimethoate or formetanate.