Florida’s commercial papaya industry may soon be hit with financial losses due to the potential of a new fungus to infect papaya trees in the state, which are grown mainly in South Florida and the warmer parts of Central Florida.
The threat comes from the phasey bean, also known as wild bush bean, which is an invasive species native to the tropical Americas and the Caribbean.
In 2017, the Florida Exotic Pest Plant Council (FLEPPC) listed phasey bean under Category II on the invasive species list, indicating that the species has increased in abundance, especially in south Florida and the Keys, but not yet altered Florida plant communities.
In the fall of 2017, leaves of phasey bean plants in Homestead, Fla., displayed powdery fungal growth, which appeared in the form of white spots on both sides of the leaves.
Plant pathologist Shouan Zhang and a former postdoctoral associate Bindu Poudel, now with the University of Arizona Cooperative Extension, conducted analysis by sequencing genes of genomic DNA and identified the fungus as Erysiphe fallax, which causes a disease known as powdery mildew.
To their knowledge, this is the first report of powdery mildew on phasey bean in the United States.
While phasey bean does not have any economic value, it may possess the ability to harm a species that does: papaya, another known host of Erysiphe fallax.
Phasey bean is prevalent year-round in south Florida, including Homestead, which contains approximately 300 acres of papaya.
If unmanaged, phasey bean could serve as a reservoir of powdery mildew with the potential to infect papaya.
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