Plant Pathology Fact Sheet
Fusarium Crown and Root Rot of Tomato in
P. D. Roberts, R. J. McGovern, and L.E. Datnoff, Respectively, Assistant Profes-
sor, Southwest Florida Research and Education Center, Immokalee, FL; Associate
Professor, Gulf Coast Research and Education Center, Bradenton, Florida; Profes-
sor, Everglades Research and Education Center in Belle Glade, FL. Revised No-
Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean
Fusarium crown and root rot, caused by the
fungus Fusarium oxysporum f sp. radicis-
lycopersici (FORL) was first detected in Florida in
1974. The disease has been reported in all major
tomato growing areas of the state, but is particularly
serious in the acidic, sandy soils of Florida's southern
production regions. Fusarium crown and root rot has
also occurred in Canada, Mexico, Israel, Japan, many
countries in Europe, and other states in this country
including California, New Jersey, New York, New
Hampshire, Ohio, Pennsylvania, and Texas. It is a
serious problem for seedling and greenhouse fruit
production, and can cause significant yield decreases
in field-grown, staked tomatoes in Florida.
The fungus invades susceptible plants through
wounds and natural openings created by newly
emerging roots. Early symptoms caused by FORL in
tomato seedlings include stunting, yellowing, and
premature loss of cotyledons and lower leaves. A
pronounced brown lesion that girdles the hypocotyl
(root/shoot junction) root rot, wilting, and death are
advanced symptoms (Figure 1).
Infected plants in the field may be stunted, and
as they begin to heavily bear fruit, their lower leaves
turn yellow and wilt (Figure 2). Wilting first occurs
during the warmest part of the day, and plants appear
to recover at night. Infected plants may either totally
wilt and die, or persist in a weakened state, producing
reduced numbers of inferior fruit.
The tap root of infected plants often rots
entirely, and chocolate brown cankers appear at the
soil line (Figure 3). When diseased plants are sec-
tioned lengthwise, extensive brown discoloration and
rot are evident in the cortex of the crown and roots
(Figure 4). In comparison with the related fungus F
oxysporum f sp. lycopersici (FOL), which causes
Fusarium wilt, FORL produces less extensive discol-
oration in the plant's water-conducting tissue; the
brown streaks observed, extend less then 20 to 30
cm. (8 to 12 in.) above the soil line. Round, brown
lesions are evident at the origins of rotted lateral roots.
An abnormal proliferation of adventitious roots may
occur above the infected region. The fungus produces
masses of white mycelium and yellow to orange
spores in necrotic stem lesions on dead and dying
Ecology and Epidemiology
In further contrast to Fusarium wilt, crown and
root rot is favored by cool temperatures (100C to
200C/500F to 680F). Low soil pH, ammoniacal
nitrogen, and water-logged soil also exacerbate the
disease. The causal fungus produces three types of
spores: macroconidia, microconidia and chlamy-
dospores. Two of these spores figure prominently in
the survival and spread of FORL. Microconidia form
in great abundance in necrotic tissue and are spread
by air currents. They readily reinfest soil sterilized by
heat or broad spectrum biocides such as fumigants.
Chlamydospores have thicker walls and enable the
fungus to survive in the soil and wooden stakes for
more than one cropping season.
Lateral spread of the pathogen from
plant to plant is primarily by root contact as
seen as the clustering of symptomatic plants
within beds (Figure 5). Movement of the fun-
gus in the soil in the absence of roots is mini-
mal (< 2.5 cm/1 in.). Long-range dissemina-
tion of FORL can occur through infected trans-
plants and perhaps via chlamydospores in soil
particles on contaminated shoes, plant stakes,
machinery, transplant trays, and other equip-
Recent analysis of a population of FORL
isolates by vegetative compatibility grouping
(VCG) and molecular techniques showed that
VCG 0094 is predominant in Florida. Two other
VCGs, 0091 and 0098, are present at low fre-
quencies. Within the VCG 0094 population, iso-
lates from the east coast are distinct from west
coast. The results from VCG and genetic analy-
sis results indicate that FORL was probably in-
troduced in Palm Beach Co., FL and moved to
other parts of the state and probably also to
Resistance has been successfully bred
into a number of greenhouse and field toma-
toes. The fungus may also infect and cause
small lesions in the roots of pepper and egg-
plant, but apparently does not infect potato.
Surprisingly, a number of nonsolanaceous
plants, including spinach, beets, many legumes,
and certain cucurbits may be infected by FORL.
The fungus has also been isolated either natu-
rally or experimentally from the roots of a num-
ber of weeds, including Brazilian pepper
(Schinus terebinthifolius), carpet weed (Mollugo
verticillata), chickweed (Stellaria media), corn
spurry (Spergula arvense), cudweed (Gnaphatium
sp.), curly dock (Rumex crispus), narrow leaved
plantain (Plantago lanceolata), redroot pigweed
(Amaranthus retroflexus), Scoparia sp., Shepard's
purse (Capsella bursa-pastoris), and wild buck-
wheat (Polygonum convulvulus). Monocots, such
as corn, apparently are not susceptible.
At present, Fusarium crown and root rot
is difficult to control in field-grown tomatoes
because the pathogen rapidly colonizes steril-
ized soil and persists for long periods. How-
ever, an integration of the following manage-
ment procedures may help to reduce the im-
pact of crown and root rot:
1. Use disease-free transplants. Transplant
houses should not be located near tomato pro-
duction fields. Avoid over watering, which
makes the transplants more susceptible to
crown and root rot. Disinfect transplant trays
by steaming before reuse.
2. Use a preplant fumigant. The soil
should be of good tilth and adequately moist
for at least two weeks prior to fumigation. Use
an appropriate chisel spacing and depth, and
immediately cover the bed with plastic mulch
3. Optimize cultural practices in the field.
Avoid injuring transplants when they are set in
the field. Physical damage and injury from ex-
cessive soluble salts may make young plants
more susceptible to crown and root rot. The
use of water drawn from wells rather than
ditches for watering-in transplants may help to
prevent recontamination of fumigated soil.
Avoid ammoniacal nitrogen and maintain the
soil pH at 6 to 7. Rapidly plow in crop debris
following final harvest. Disinfest tomato stakes
before reuse, or use new stakes.
4. Rotate with a nonsusceptible crop. In-
complete knowledge of the host range of FORL
makes precise recommendations in this area
difficult. Current research suggests that legu-
minous crops should be avoided in favor of
corn and similar crops. Rotation and intercrop-
ping with lettuce has reduced FORL in green-
5. Significant progress has been made in
breeding for resistance to Fusarium crown and
root rot in field-grown tomatoes. Although the
commonly used commercial varieties do not
have resistance, some resistant cultivars, such
as Conquest, are available for field use.
Additional management strategies un-
der investigation include the use of biological
control, cover crops, and soil solarization alone
or in combination with fumigants.
Figure 1. Infected tomato transplants (left
and center) next to healthy transplant (right).
Figure 2. Infected plants exhibiting wilting of lower leaves.
Figure 3. External discoloration extending Figure 4. Internal discoloration of the crown
above the crown of an infected tomato. and root rot. (Note missing taproot).
* .r,. .. .
Figure 5. Lateral spread of Fusarium oxysporum f.sp. radicis-lycopersici
within a planting bed.