Spinach the cure for citrus greening?

A possible solution to a serious problem is a bit offbeat.

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Citrus greening is a worldwide problem that adversely affects oranges well as other citrus trees. Even if you don't live in a climate where you can grow these trees outdoors, this matters to you if you drink orange juice, buy citrus fruits, use potpourri, or grow orange, lemon, or grapefruit plants indoors.

But there's some good news about this devastating problem, which is spread by Asian citrus psyllids, tiny insects about the size of gnats.

You can read all about citrus greening at the USDA's Cirtus Alert website, which explains the threat and shows where the malady and the psyllids have been found.

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The site also lists high-risk activities that can spread citrus greening -- including adverse actions gardeners might unwittingly take:

1. Such as bringing back a cute little orange tree houseplants from your winter vacation in Florida, for instance. Miniature lemon, lime, and grapefruit trees are tempting, too -- and also to be avoided.

2. Don't order citrus plants of unknown origin. Actually, it's a good idea also to ascertain the source of all citrus plants you might be considering from a mail-order source, no matter where it's located.

3. Don't even take an individual orange, grapefruit, kumquat, or other citrus fruit out of Florida unless it's been inspected and passed by the USDA.

4. You'll also want to watch out for citrus relatives that can host citrus greening disease: mock orange, curry leaf, orange jasmine, and orange boxwood.

If you live in a citrus-growing state, you may want to be aware of the USDA's list of online resources.

But there is now hope for a citrus greening cure, Susan Salisbury reported in the Palm Beach Post earlier this month. The surprising answer may be inserting spinach genes into citrus plants.

"Proteins called defensins fend off bacteria, and the defensins spinach makes have 'broad spectrum anti-microbial properties,' " explains Erik Mirkov, Texas A&M plant pathologist and microbiologist.

"In the lab, the spinach gene was inserted into citrus chromosomes that were then grown into tiny trees -- tiny trees with apparent resistance to greening and canker, at least in the lab.

"When the [greening] bacterium sees the spinach defensin, it has never seen that before in citrus and doesn't know how to get around it," Dr. Mirkov says.

This is fascinating stuff, but it takes time, of course. Until the effectiveness of spinach is known -- and regulators have approved its use -- the Florida citrus industry will continue to use defensive methods.

(NOTE: To go to the Monitor's main gardening page -- which contains articles and blog posts on many topics -- click here.)

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