By John Olive, Director, AU Ornamental Horticultural Research Center | CoastalAlabamaGardening@gmail.com

Q: I read about growing citrus in a recent issue of Lagniappe, and would like to plant one but my neighbor told me about a serious citrus disease that could kill my trees. Is it worth the risk to plant a satsuma?

A: The short answer is yes, it is still worth the risk to plant citrus on the Gulf Coast, even though the destructive disease known as citrus greening, huanglongbing (HLB) or yellow dragon has been devastating everywhere it has occurred, and has recently been found in both Mobile and Baldwin counties.

It is caused by a bacterium that gets into the vascular system of citrus trees, such as satsumas, lemons and grapefruit. It is spread by the Asian citrus psyllid (ACP), a tiny insect that feeds on infected trees and can then infect healthy trees by feeding on them.

The ACP is a tropical to semi-tropical insect, and while not common here it has been found in South Alabama since at least 2010. Home gardeners should regularly scout for this insect, especially during growth flushes. Adults and nymphs can be found feeding on the succulent new growth, and nymphs often excrete characteristic waxy threads.

I don’t want to downplay the potentially catastrophic effects this disease could have on citrus in our area, but there is some encouraging news. Citrus are not as heavily planted in South Alabama, so tree-to-tree spread of the disease may be slower than in areas where commercial citrus is concentrated. Also, if you are looking for the bright side of our recent bone chilling weather, severe cold winters appear to greatly reduce populations of ACP as well as reducing sources of disease by killing stressed and diseased citrus trees.

It is difficult to make a definite citrus greening diagnosis without laboratory confirmation. Unfortunately, the symptoms of this disease can often be confused with nutrient deficiencies and leaf miner damage, which are much more common.

Some leaf symptoms to look for include irregular yellowing, leaf veins that have a raised, corky appearance and yellow leaves with green spots or “islands.” Symptoms on the fruit include uneven ripening and lopsided, misshapen fruit with black aborted seed. Fruit is also bitter and inedible.

The trees may initially appear healthy, with only a single branch of bright yellow leaves, but as the disease progresses, dieback and death of the tree will follow. It can take years for an infected tree to die and during that time it is a reservoir for the ACP to feed on and spread the disease.

Because the symptoms are often unclear, home gardeners should focus on scouting for the ACP to slow the spread of disease and only buy inspected citrus from a known source. There is no cure once a plant is infected; diseased trees must be removed and destroyed.

Only a handful of trees out of thousands surveyed along the Gulf Coast were found to be infected, so it is unlikely you have a tree with the disease now. If you suspect you have citrus greening disease, contact the Alabama Department of Agriculture and Industries (ADAI) at 334-240-7228 so they can help you determine if an inspector needs to collect a sample, or ask that they include your citrus in their database for possible inspection when ADAI makes its annual citrus survey inspection.

For more information and images of citrus greening and the Asian citrus psyllid, visit edis.ifas.ufl.edu or www.SaveOurCitrus.org.

YOU ARE INVITED TO THESE UPCOMING GARDENING EVENTS
What: Extension Pruning Demonstration for Fruit Crops, Roses and Ornamentals
When: Monday, Feb. 19, 9-11 a.m.
Where: Jon Archer Ag Center, 1070 Schillinger Road N., Mobile
More: Free, bring your pruning shears. Call 251-574-8445 for more info.

What: Mobile Master Gardeners Lunch & Learn (Free)
When: Monday, Feb. 26, noon to 1 p.m.
Where: Jon Archer Ag Center, 1070 Schillinger Road N., Mobile
Topic: Landscape and Tree Initiatives in Mobile, Brian Underwood and Matt Jollit

Master Gardener Helpline: 1-877-252-4769 or send gardening questions to coastalalabamagardening@gmail.com.

Photo/Courtesy of John Olive