'Silver bullet' kills phytophthora, a fungus that affects more than 400 plants and trees

Ali and a team of researchers with UF's Institute of Food and Agricultural Sciences, along with the University of Central Florida and the New Jersey Institute of Technology, have found that silver nanoparticles produced with an extract of wormwood, can stop several strains of the fungus phytophthora dead in its tracks.

Phytophthora attacks the leaves and roots of more than 400 plants and tree varieties -- everything from tomato plants to oak trees -- threatening the Florida's $15 billion-a-year ornamental horticulture industry.

"The silver nanoparticles are extremely effective in eliminating the fungus in all stages of its life cycle," Ali said. "In addition, it had no adverse effects on plant growth."

Wormwood is an herb naturally found in the foothills of Himalayas in the Indian subcontinent and is known to have strong antioxidant properties.

Ali said the silver-wormwood nanoparticles can be used as economical and eco-friendly alternatives to chemical pesticides. The silver nanoparticles measure 5 to 100 nanometers in diameter (20 nanometers is about the thickness of a cell wall) and are sprayed onto a plant. They then shield the plant from the fungus.

Silver nanoparticles are currently being investigated for applications in various industries, including medicine, diagnostics, cosmetics and food processing. They are already used in wound dressings, food packaging and in consumer products like textiles and footwear for fighting odor-causing microorganisms.

Since the silver nanoparticles display multiple ways of inhibiting fungus growth, the chances of pathogens developing resistance to them are minimized, Ali said. Because of that, they may be used for controlling fungicide- resistant plant pathogens more effectively.

Worldwide crop losses due to phytophthora fungus diseases are estimated to be in the multibillion dollar range, among them $6.7 billion in losses in potato crops due to late blight (which caused the Irish Potato Famine between 1845 and 1852 when more than one million people died) and $1 billion to $2 billion in soybean loss.

Other members of the research team were: Mohammad Ali, David Norman and Mary Brennan with the University of Florida's Plant Pathology-Mid Florida Research and Education Center; Bosung Kim with the University of Central Florida's chemistry department, Kevin Belfield with the College of Science and Liberal Arts at the New Jersey Institute of Technology and the University of Central Florida's chemistry department.

The team's work was published this month in the journal Phytopathology. They now hope to develop these nanoparticles into a commercial product for use in controlling phytophthora diseases in plants.