USDA confirms first findings of citrus black spot disease in Florida
by Christina DiMartino | May 11, 2010
A U.S. Department of Agriculture announcement April 8 confirmed the finding
of black spot fungus (Guignardia citricarpa) in a commercial citrus grove in
Immokalee, FL. As of May 10, 11 cases of the disease had been confirmed.
Considered an exotic disease, black spot symptoms include dark, speckled
spots or blotches on the rinds of citrus fruits. It is an economically significant
citrus disease in that it causes early fruit drop, reduces crop yield and renders
the highly blemished fruit unmarketable in the fresh market.
While all commercial citrus cultivars are susceptible to citrus black spot, the
most vulnerable are lemon and late-maturing citrus varieties like Valencia
The Florida discovery was made during a routine survey requested by a
grower in early March. An inspector from the Florida Department of
Agriculture & Consumer Services' Division of Plant Industry's Health Response
Program collected a suspect sample from a commercial Valencia orange
grove in Florida's Collier County. While the initial laboratory analyses by
FDACS-DPI confirmed the black spot finding, subsequent testing by the
USDA at the Beltsville, MD, laboratory provided the final confirmation.
This marks the first confirmed find of this fungal pathogen in North America
and constitutes a major jump in its geographical range.
Federal and state agriculture officials have joined forces to address the
challenges this new citrus disease presents. Rebecca Bech, deputy
administrator for APHIS' Plant Protection & Quarantine program, said in the
USDA's statement, "We are working in collaboration with the FDACS, the
University of Florida's Citrus Research & Education Center and the citrus
industry to limit the spread and impact of this disease through swift
regulatory actions, education and informed compliance."
The efforts to date include delimiting surveys at arcs around the positive
finds at multiple mile ranges, identifying other high-risk areas for the survey,
inspecting shipments received at packinghouses and processing plants,
inspections at all lemon groves in Florida, and surveying residential areas
surrounding the positive find areas.
APHIS has also issued Emergency Action Notices to five groves within the
one-mile arc around the initial detection area and to processing facilities that
receive fruit from those groves. Such notices specify the requirements for
moving fruit, the decontamination treatment requirements for equipment and
how leaves and other plant debris remaining in trailers and field boxes are to
be treated and destroyed.
"Discovering black spot in a Florida grove is one in a long line of challenges
brought on by fair trade," Terence McElroy, department press secretary for
the FDACS, told The Produce News. "You can take all of the weather-related
problems the agriculture industry has faced over the years, including
hurricanes, and still the biggest challenges come from diseases and pests
that enter the country on imported products. The federal government, which
has the responsibility of protecting our border, cannot possibly inspect every
package or piece of fruit that comes in to the U.S."
Mr. McElroy said that copper spray is currently being used on trees that are
located in a susceptible range of the black spot find. The effort helps make
trees fairly resistant to the fungus. The spray is the same type that is used to
help protect trees from citrus canker, which is a bacterial disease.
"But copper spray does not kill black spot on trees that are infected," he
added. "A number of fungicides are being studied now, and our agency and
growers will be seeking [U.S. Environmental Protection Agency] approval very
shortly to use one or more of them in the field."
Despite the many challenges the Florida citrus industry has faced in the past
15 years, when all the ancillary and far-reaching business the industry
conducts is added up, it continues to be an approximately $8 billion- to $10
"Actual acreage is down from 900,000 to about 600,000 over the past
decade, so there has been certainly shrinkage in those terms," said Mr.
McElroy. "But prices over the last 15 years have increased. And in terms of
efficiency, we're producing as much citrus on less acreage today than we were
when acreage was at its peak."
The USDA indicated that a forensic investigation is underway that aims to
determine the origin of the black spot infection. The next steps include the
appointment of the Citrus Health Response Plan working group to focus on
citrus black spot regulations, research and outreach initiatives.
Citrus black spot occurs in subtropical regions of the world with summer
rainfall. The disease has been found in Argentina, coastal areas of Australia,
Brazil, China, Indonesia, Japan, Kenya, Mozambique, Nigeria, the Philippines
and areas of South Africa, Swaziland, Taiwan, Uruguay, Venezuela and