Florida Researchers Help Ornamental Growers Reduce Fungicide Use In Phytophthora Control

Florida Researchers Help Ornamental Growers Reduce Fungicide Use In Phytophthora Control

Phytophthora On Poinsettia

Photo credit: UF/IFAS

New research from the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFS) may help ornamental growers control various phytophthora species, which can infect anything from landscape trees to poinsettias to small indoor flowers and cause millions of dollars in damage annually. The findings could help growers ultimately reduce fungicide use to control phytophthora.


“We found that some phytophthora strains were resistant to a specific kind of fungicide,” says G. Shad Ali, an assistant professor of plant pathology at the UF/IFAS Mid-Florida Research and Education Center in Apopka, Florida.

“Luckily, they were controlled by at least another kind of fungicide. This information is hugely important in letting growers and pesticide applicators know not to use the same kind of fungicides always, but to rotate different kinds of fungicides.

“Fewer fungicides are good for everybody, including nurseries, who would reduce the cost of production, and they are good for consumers, who would pay less for ornamentals,” Ali says.

For their latest study, UF/IFAS scientists, led by Ali, wanted to answer two questions:
• How diverse are the genes of phytophthora that harm ornamental plants in Florida?
• How many fungicide-resistant types of phytophthora are there?

They found a wide range of genetic diversity among these fungi, which could contribute to aggressiveness of phytophthora, provided they crossbreed and exchange their disease-causing genes, Ali says. Scientists also say their findings suggest the need to find more phytophthora-resistant genes and beneficial microbes, which may be the best and natural way to control phytophthora.

In addition to finding fungicides that can kill phytophthora species, scientists also are examining integrated pest management methods as a way to control diseases, including diagnosis, sanitation, prevention, using beneficial microbes, fungicides, and resistant plant cultivars, Ali says. They are also trying to find ways to produce phytophthora-free plants and to prevent the spread of phytophthora.

The study is published online in the journal Plant Disease.