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Can lasers help treat diseased Florida orange trees?

"Effective treatment of this disease has largely been limited by the inability to deliver antibacterial substances," said researcher Ed Etxeberria.
By Brooks Hays   |   Jan. 13, 2016 at 5:26 PM

GAINESVILLE, Fla., Jan. 13 (UPI) -- Citrus greening is a bacterial disease that affects citrus trees all over the world. Once infected, the pathogen diminishes fruit production and eventually kills the tree.

Experimenting with ways to combat the disease, researchers at the University of Florida happened upon unique and promising combination -- lasers and antibiotics.

The pathogen succeeds by attacking the veins in the tree's inner bark, called phloem. In disrupting the tree's vascular system, the disease prevents new roots and fruits from getting an adequate supply of sugar.

Diseased trees put out shrunken, bitter fruits and are slowly starved to death. Citrus greening, also known as Huanglongbing, has cost Florida's citrus industry millions of dollars.

Scientists first began using lasers to etch identification marking in the leaves of citrus trees. But they realized the technology could potentially be used to more effectively deliver medicine.

"Effective treatment of this disease has largely been limited by the inability to deliver antibacterial substances to the phloem," researcher Ed Etxeberria, a plant physiology professor at Florida's Citrus Research and Education Center, said in a press release. "Penetration of externally applied substances into trees is generally prevented by the presence of protective layers on leaves."

Lasers can make precise incisions in plant tissue, penetrating at exact depths and as shallow as a single cell. The technique allows antibiotics to be administered directly to infected tissue, bypassing protective layers.

Researchers used dyes to study how deep the antibiotics were able to penetrate into the tissue of young Valencia orange trees. Early results are promising, but more testing is needed. Oils helped repair laser incisions and prevent permanent damage.

"For large-scale field applications, a scaled-up and more flexible model of the instrument containing multiple nozzles for the laser light, antimicrobial spray, and wax application is being developed," said Etxeberria. "The overall system offers the added advantage of lower application frequencies and hence reduction in chemical use, a condition that lessens environmental impact."

The laser application technology was detailed in a new paper, published this week in the journal Applications in Plant Sciences.

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