Origin: Southeastern Asia
(spread to Japan, South Africa, Australia, the Pacific Islands,
and South America)
Impact: Citrus Canker is one of the most destructive
agricultural diseases. It is caused by the bacterium Xanthomonas
It is highly contagious among trees and produces scab-like
lesions on fruit, stems, and leaves. An infection may cause
defoliation, dieback, severely blemished fruit, reduced fruit
quality, and premature fruit drop.
Citrus Canker was first found in the U.S. in 1910, but was
subsequently declared eradicated after millions of citrus
and nursery trees were burned.
Today, the disease still exists in Florida and continues
to threaten valuable citrus crops. It can be spread over short
distances by severe wind and rain, flooding, air currents,
insects, birds, and human movement within groves.
When an area is suspected of being infested with citrus canker,
fruit or leaf samples are sent for testing by state and federal
Xanthomonas axonopodis, pathovar citri
Photo courtesy of the U.S. Department of Agriculture