Disease puts squeeze on Florida's citrus trees

I used to think citrus trees were the only fruit trees that could grow well and live long lives in the Tampa Bay area without help from pesticides.

But citrus greening disease has taken hold in Florida, and that makes growing the Sunshine State's signature fruit tree more problematic. We can no longer plant an orange or grapefruit tree in the backyard and feel confident it will give us bags of bounty for years to come.

The disease, first spotted in Florida in 1998, can cause trees to rapidly decline. Young trees may never produce the first fruit, and mature trees may stop producing. What fruit they do bear tends to remain green (hence the disease name).

It's an incurable bacterial disease that is spread by a tiny insect called the Asian citrus psyllid. The good news right now is that the very low temperatures we had this month may have knocked the little psyllid back for a while. The bad news is, it will return.

More bad news: There are no citrus varieties known to be resistant to greening disease, although the key lime may be less susceptible than others.

More photos of what citrus greening looks like can be found on the Web at edis.ifas.ufl.edu/hs383. If you have a citrus tree that you suspect has greening disease, call 1-800-282-5153, and the Florida Division of Plant Industry will help with verification. If your tree has the disease, it should be removed and disposed of per DPI recommendations.

Another bacterial disease that has become a serious problem is citrus canker. The bacteria are not spread by an insect but by wind-driven rain. Consequently, if a citrus tree in your yard is not close to other citrus trees, or if there's a windbreak between trees, it's less likely to become infected.

A tree that has canker disease may drop fruit prematurely, but otherwise the damage is cosmetic. Scablike lesions form on the fruit surface, but the fruit is still edible and usable for juice. Sprays containing copper can be applied to the developing fruit to limit the number of lesions that develop.

Tangerines are least susceptible to canker disease, followed by Valencia orange and tangelos. Lemons and Navel, Pineapple, and Hamlin oranges are moderately susceptible, while grapefruit and key limes are highly susceptible to canker.

All citrus trees for sale are required to have tags showing the registration number of the propagating nursery. This is important because the tag lets you know that the tree has been certified free of greening and canker diseases. And, certainly, if you are going to have success with citrus, you need to start off with a healthy tree.

The next must-haves: proper irrigation, fertilization, and weed control. For help, see the online article "Citrus culture in the home landscape" at edis.ifas.ufl.edu/hs132.

Citrus may not be the carefree fruit tree it once was, but it still deserves a place in the home landscape. Many of us grow plants we love but have to replace occasionally. Just take a walk around your neighborhood now and you'll see them.

The fragrance of citrus blossoms and the flavor of fresh squeezed juice are just too good to pass up.