Fusarium Rots in Processing Tomatoes
» Fusarium crown and root rot and Fusarium foot rot are important root infecting diseases of tomato.
» Fusarium crown and root rot causes symptoms similar to those of Fusarium wilt.
» Management strategies for both of these rot diseases focus on minimizing the spread of the pathogens.
FUSARIUM CROWN AND ROOT ROT
Fusarium crown and root rot is caused by the fungus
Fusarium oxysporum f. sp. radicis-lycopersici, a close relative of
the Fusarium wilt pathogen. Fusarium crown and root rot
(FCRR) has become one of the most damaging soilborne
diseases of tomato.1 FCRR is found in most of the major
tomato growing regions of the world, including the U. S.,
Canada, Mexico, Israel, Japan, and many countries in Europe.
In the U. S., the disease occurs in California, Colorado,
Florida, New Jersey, New York, New Hampshire, Ohio,
Pennsylvania, and Texas.1,2,3 FCRR is becoming more
common and widespread in California and Florida. The
disease causes significant yield losses in both greenhouse
and field-grown tomato production systems, and yield
reductions of 15 to 65% have been reported.1,4
Symptoms, including yellowing and premature dropping of
cotyledons, can be seen on infected seedlings at the time of
transplanting.3 However, symptoms typically begin to show
when plants are nearing the mature-green fruit stage. On
these more mature plants, the initial symptoms include a
yellowing of the oldest leaves. The yellowing gradually
progresses up the plant to the younger leaves as the
disease develops, and symptoms may be restricted to a
single branch of the plant (Figure 1).2,5 Affected leaves
may wilt during the heat of the day but recover overnight,
and in some cases, flowers may wilt and die. These
symptoms are similar to those associated with Fusarium wilt.
Prominent lesions develop on the hypocotyl (lower stem)
and on the tap- and lateral-roots (Figure 2A). These lesions
are typically round in shape and chocolate brown in color.
A brown discoloration in the cortex (Figure 2B) can extend
beyond the externally visible lesions, up to 10 inches above
the soil-line, but the discoloration will not move up into the
upper parts of the plant as is seen with Fusarium wilt.2,3
Adventitious roots may proliferate above the affected stem
tissues, and sometimes white mats of fungal growth with
pink spore masses will develop on dead tissues. Plants can
be killed by FCRR when the disease is severe.
The FCRR pathogen survives in the soil as spores and on the
roots of alternates hosts including eggplant, peppers, some
legumes and cucurbits, beets, spinach, carrot, cabbage,
wheat, and several weed species. The pathogen can spread
by infected transplants and through the movement of
infested soil and equipment.1,2
The FCRR pathogen infects tomato root systems through
wounds created by emerging lateral roots. Infection and
disease development are favored by cool temperatures (59 °
to 68 °F). The disease develops best in areas with low soil pH
levels, high chlorine salt levels, applications of ammonia
forms of nitrogen, and water-logged soils. The pathogen can
spread from plant to plant during the season through root
contact.1,2 The pathogen can also spread through wind-
blown spores to re-infest steam-sterilized or fumigated soils.
Management strategies for FCRR focus on preventing
infection and limiting the spread of the pathogen.1 Growers
should plant only pathogen-free seed and transplants.
Transplant production houses should not be located near
production fields, and stringent sanitation practices,
including disinfecting pots and trays and cleaning and
sanitizing benches and tools, should be used between
transplant crops. Avoid overwatering transplants, as that
makes them more susceptible to FCRR. Transplant seedlings
when soil temperatures are above 68 °F, and avoid injuring
seedlings during transplanting. 1,2,3
In the field, maintain soil pH levels in the 6 to 7 range, and
avoid the use of ammonia–based fertilizers. Minimize plant
stress throughout the growing season. Incorporate crop
debris promptly after harvest to promote rapid
decomposition. Long-term rotation to non-host crops, such
as corn and other monocots, can help prevent the buildup
of inoculum in the soil. Soil fumigation is usually not effective
for controlling FCRR because the fungus can quickly
recolonize fumigated soil. A single dominant gene for
resistance to FCRR (Fr1) has been identified, and it is used in
some tomato varieties. However, most commercial tomato
varieties are susceptible to this disease.1,2,6
FUSARIUM FOOT ROT
Fusarium foot rot (FFR) is caused by the fungus Fusarium
solani f. sp. eumartii, which also causes Eumartii wilt on
potatoes. This pathogen also infects the roots of peppers
and eggplant. FFR occurs in Australia, India, Israel, Ivory
Coast, Turkey, and the U.S.2,7
The root symptoms of FFR include reddish- brown
lesions moving into the cortex of tap roots and large
lateral root (Figure 3). Vascular discoloration can be
seen extending 1 to 4 inches above and below the
externally visible lesions.2 Foliar symptoms of FFR
distinguish this disease from FCRR and Fusarium wilt. Leaves
of FFR infected plants show interveinal chlorosis and
necrosis (Figure 4). These foliar symptoms are often
restricted to a single branch, at least initially. As the root rot
phase advances, the leaves turn brown and collapse, but
plant death is unusual.2
The FFR fungus can survive in the soil for two to three years
in the absence of a susceptible host. However, the fungus
can survive on a wide range of plant species, even though it
does not cause disease symptoms on most of them. Once
introduced into an area, the FFR pathogen is difficult to
eradicate. Like the Fusarium crown rot pathogen, this fungus
infects through naturally occurring root wounds. In
California, the disease is most severe at temperatures
between 77 ° and 86 ° F. In Australia, the severity of the
disease increases as the temperature decreases to 59 °F.2
All currently available commercial tomato varieties are
susceptible to Fusarium foot root. However, some varieties
are more tolerant of the disease than others.2 Rotation to
non-host crops for at least four years can help prevent the
buildup of inoculum in the soil. Some studies have shown
partial control of FFR using a combination of fungicide
applications following soil fumigation or soil solarization
treatments. The primary strategy for managing Fusarium foot
rot in commercial tomato operations is to limit the spread of
the pathogen within and between fields by minimizing the
movement of infested soil. This requires the thorough cleaning
of equipment and workers shoes and clothing before entering
pathogen free areas.
1 Ozbay, N. and Newman, S. 2004. Fusarium crown and root rot of tomato and control methods. Plant Pathology Journal 3(1):9-18.
2 Jones, J., Zitter, T., Momol, T., and Miller, S. 2014. Compendium of tomato diseases and pests, 2nd Ed. American Phytopathological Society, St. Paul.
3 Zhang, S., Roberts, P., McGovern, R., and Datnoff, L. 2014. Fusarium crown and root rot of tomato in Florida1 2 UF-IFAS Extension. PP52.
4 Davis, R. M., Miyao, G., Subbarao, K., Stapleton J., and Aegerter, B. 2103. Tomato: Fusarium crown and root rot. UC Pest Management Guidelines.
5 Davis, R. M., Miyao, G., Subbarao, K., Stapleton J., and Aegerter, B. 2103. Tomato: Fusarium foot rot. UC Pest Management Guidelines.
6 Vakalounakis D. 1988. The genetic analysis of resistance to Fusarium crown and root rot of tomato. Plant Pathology 37:71-73.
7 Romberg, M. K., and Davis, R. M. 2007. Host range and phylogeny of Fusarium solani f. sp. eumartii from potato and tomato in California. Plant Dis. 91:585-592.
For additional agronomic information, please contact your local seed representative. Developed in partnership with Technology Development & Agronomy by Monsanto.
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