Plant Pathology Fact Sheet
Brown Stem in Florida Celery
Ken Pernezny, Lawrence Datnoff, Richard Lentini, and Mark Sommerfield, Re-
spectively, Professor, Professor, Sr. Biological Scientist; Everglades Research
and Education Center, Belle Glade, FL 33430; University of Florida, Gainesville,
32611., and former Plant Pathologist, A. Duda and Sons, Belle Glade, FL 33430.
1997; Revised November 1999.
Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean
Sporadic outbreaks of a petiole necrosis
of celery (Apium graveolens var. dulce), known
locally as "brown stem", have been observed
in Florida for over 40 years. In the 1992-93 win-
ter vegetable season, a particularly severe out-
break of brown stem occurred in celery produc-
tion fields throughout the Everglades Agricul-
tural Area (EAA). One hundred percent of all
fields surveyed had some brown stem, with av-
erage incidence about 5%. Losses to the indus-
try were estimated at $5 million. At that time,
no specific cause for brown stem had been es-
tablished. The prevailing opinion was the dis-
ease was an environmental or physiological
problem. The severe outbreak prompted a
more thorough investigation into its cause. The
research uncovered a common bacterial patho-
gen as the origin of the disease.
Brown stem symptoms consist of a firm,
brown discoloration throughout the petiole.
Damage is especially evident in the heart re-
gion at the base of the stalk, but brown streaks
may be seen along most of the length of the
petiole (Fig. 1 and Fig. 2). Browning is confined
to the ground parenchyma; vascular bundles
appear as islands of healthy green among dis-
eased cortical and pith tissues (Fig.3). The
symptoms become more pronounced as celery
approaches harvest maturity.
Causal Agent Isolated and Identified
The isolation and identification of the
causal agent of brown stem was recently made.
It was demonstrated that brown stem disease
of celery is caused by the bacterium Pseudomo-
nas cichorii. This is the same pathogen that
causes bacterial blight of celery (See Paint Pa-
thology Fact Sheet no. pp-8). Indeed, tests con-
firmed that bacterial strains recovered from
brown stem lesions are indistinguishable from
those causing typical bacterial blight lesions on
celery leaf blades.
Spread of the Disease
Reports of brown stem are made only
about every five or six years, whereas leaf spot
symptoms caused by Pseudomonas cichorii are a
yearly occurrence. The reasons for the sporadic
nature of brown stem outbreaks are unknown.
The weather in the winter of 1992-93 was un-
usual, with frequent rainfall and strong winds.
These conditions, along with high humidity,
might be essential for brown stem expression.
Documented reports of weather conditions
linked to brown stem incidence are lacking.
Identification of environmental conditions im-
portant to brown stem development is the sub-
ject of current research.
Prevention and Control
Do not apply foliar nitrogen during sea-
Figure 1.Brown streaks along of celery with
brown stem damage.
sons favorable for bacterial blight and avoid
over-fertilization with soil- applied nitrogen. To
help prevent the spread of the bacterium keep
workers and farm equipment from brushing
against wet plants. Cultivar differences in
brown stem susceptibility have been identified
by plant breeders at the EREC in Belle Glade.
Figure 2. Brown stem damage in celery.
Figure 3. Brown stem cross section.