News on the Grow

March 21, 2003 - 09:52

Ralstonia Outbreak

Several U.S.
growers can now add a new disease to their repertoire: Ralstonia solanacearum biovar
3 race 2. One of the vascular, bacterial agents that causes southern bacterial
wilt, R. solanacearum biovar 3 race 2 was recently discovered in a limited
number of geranium cuttings that were produced offshore, shipped to U.S.
rooting stations and eventually rerouted throughout the Eastern, Southern and
Midwestern United States.

Because of its inclusion in the U.S. Agricultural
Bioterrorism Protection Act of 2002 as "potentially posing a severe threat
to plant health or plant products," this most recent disease importation
caused a reaction from Animal and Plant Health Inspection Service (APHIS) and
United States Department of Agriculture (USDA) and a temporary quarantine of
hundreds of greenhouses.

How it Happened

The disease originated from a minor infestation of seven
confirmed 'Americana Dark Red' geranium stock plants in Goldsmith Plants'
Kenyan facility. According to Goldsmith's Don Snow, less than 100 cuttings were
taken from the contaminated stock plants and unintentionally introduced into the
United States in a routine shipment during weeks 44-46 (October 27-November 16)
to two U.S. greenhouses, Glass Corner Greenhouse in Michigan and Pleasant View
Gardens in New Hampshire. Plants were rooted for five weeks and subsequently
shipped to customers during weeks 49-51 (December 1-December 21).

On February 10, the USDA Plant Protection and Quarantine
(PPQ) Center officially confirmed the presence of R. solanacearum biovar 3 race
2 in samples collected from greenhouses in Wisconsin, Indiana and Illinois.
After the February 13 destruction of approximately 50,000 cuttings (total) at
Glass Corner and Pleasant View, both operations resumed shipping cuttings that
had not originated in Kenya.

On February 14, the USDA stopped all geranium shipments from
Kenya to the United States until further notice. This has impacted Goldsmith,
Fischer and Oglevee, which each have stock facilities in Kenya. As of press
time, there have been no reported outbreaks at any of the other breeders, and
this quarantine is not expected to dramatically impact the 2003 seasons.

The last date of importance is the February 27 release of
the USDA/APHIS action plan. At approximately 35 pages long, the action plan
gives a detailed account of how to respond to symptoms. As much of this
information is of importance only to those greenhouses on the quarantine list,
we will not go into the details of the Plan in this article. Those interested
can find the Action Plan at any of the Web sites listed at the end of this
article. You can also find a 12-page summary of the Plan at the Society of
American Florists' (SAF) Web site.

Because of commingling, and possible cross contamination,
during rooting and shipping to and from Glass Corner and Pleasant View, the
number of greenhouses receiving suspect plants is expected to number
approximately 150 but could be as many as 800. While these greenhouses are
currently under quarantine, time and testing have revealed relatively few confirmed
cases of R. solanacearum biovar 3 race 2.

It is important to remember that the only greenhouses that
should be placed under quarantine are those that received geranium cuttings
from Glass Corner between November 4, 2002 and January 24, 2003 (weeks 45-4) or
from Pleasant View between November 4, 2002 and February 14, 2003 (weeks 45-7).

What Happens Next?

The nearly two-week delay between the first notice of the
disease and the follow-up is due to the complexity of the situation and the
agricultural security concerns. Ralstonia solanacearum biovar 3 race 2 was
placed on the bioterrorism list because it is devastating to important
agriculture crops such as potatoes, tomatoes, beans and tobacco, and as such,
USDA/APHIS needed to take extra precaution to ensure the protection of these
crops.

APHIS has worked with states and scientific authorities and
gotten information from the industry (most notably Goldsmith, SAF and the two
effected rooting stations) to develop a plan that will be as workable for
growers as possible, yet ensure disease eradication. In the interim, the delay
has led to uncertainty for both state regulators and the geranium industry.

Fearing that any introduction of Ralstonia on geranium
cuttings could damage the U.S. potato industry, some have urged that all
imported cuttings be banned -- a move that was introduced last year and one
that would cause substantial disruption of the nearly $300 million U.S.
geranium industry.

"Long term," explained SAF Senior Director of
Government Relations, Lin Schmale, "we are working to get USDA to provide
official recognition to the Geranium Bacterial Disease Initiative. Currently,
the major breeding companies have voluntarily formed a committee for the
self-regulation of clean stock facilities and virus indexing to prevent the
importation of diseases such as Xanthamonos and Ralstonia."

"In the future," continued Schmale, "we think
official recognition is necessary for the continued importation of cuttings to
sustain the geranium market, 50 percent of which originates offshore. APHIS
recognizes that the geranium industry is important so they are going to work
with us to solve the problem we have right now, and they are going to continue
to work with us to set up a system whereby we can ensure that geranium cuttings
will continue to come into the United States."

What to Do

Though it is expected that the current outbreak will be
contained by publication, growers still need to watch their crops for any
geranium or nicotiana plants that show signs of disease under the warm
temperatures necessary to finish a good geranium crop.

Symptoms of Ralstonia solanacearum biovar 3 race 2 are
reportedly similar to those of Xanthamonas, another strain of southern
bacterial wilt, and include wilting plants and abnormal yellowing of leaves.
This strain of Ralstonia doesn't spread easily from plant to plant, except
through recirculated irrigation water or stem-to-stem transmission via cutting
knives or manual cleaning and pinching when the laborer has not sanitized
between plants. R. solanacearum biovar 3 race 2 can tolerate much cooler
temperatures than other strains, though it remains dormant in the cold. It can
also lay dormant in soil and water indefinitely. Growers can easily avoid
spreading the disease by simply removing and isolating wilted plants and
avoiding subirrigation of geranium and nicotiana plants.

If you suspect you might have R. solanacearum biovar 3 race
2, contact Goldsmith Plants at (800) 549-0158, your local university extension
agent or APHIS at (301) 734-3266. Other good sources of information include:
APHIS headquarters, www.aphis.usda.gov/ppq; the National Plant Protection Organization's
Phytosan-itary Alert Web site, www.pestalert.org; the Society of American Florists, www.safnow.org;
American Nursery and Landscape Association, www.anla.org; OFA, www.ofa.org; and
Purdue University, www.ppdl.purdue.edu/ppdl/hor03/02-24.html.

--Bridget White

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