UF UNIVERSITY of
2006 Florida Plant Disease Management Guide: Spinach1
Richard Raid and Tom Kucharek2
Specific Common Diseases
Damping-off (Rhizoctonia solani and
Symptoms: Damping-off disease affects young
plants during or after emergence. The causal fungus
invades the seed, emerging root, or stem and will
rapidly rot the plant. Emerged plants are often
invaded at the soil line where a maroon to
reddish-brown lesion (Rhizoctonia) will develop that
girdles the stem and causes a seedling to wilt to death.
Pythium causes a soft lower stem decay that may be
greasy-black in color.
Cultural Controls: Insure that all previous crop
and weed debris has completely decomposed prior to
Chemical Controls: See PPP-6.
Downy Mildew (Peronospora farinosa f. sp.
Symptoms: Lesions begin as indefinite yellow
blotches on the upper leaf surface. As infection
proceeds, the lower surface of these spots becomes
covered with a purplish mat of fungal sporulation.
Infection and disease development can be rapid
resulting in blackened leaves and/or dead plants,
especially during wet weather periods. Under less
favorable weather, infected plants exhibit stunting
and creamy yellow leaves.
The pathogen is an obligate parasite that over
seasons in spinach, spinach seed, and through sexual
spores in the soil. At least three races of this pathogen
are known to exist. Preferred weather for fungal
reproduction is between 45-590 F. Infection requires
a wet leaf surface.
Cultural Controls: Exercise crop rotation to
avoid overlapping winter and spring spinach crops.
Hot water treatment of seed at 1220 F for 25
minutes will eradicate the seedbore presence of this
fungus. Host plant resistance is available, but the
development of new races may limit effectiveness.
Chemical Controls: See PPP-6.
Mosaic (Cucumber mosaic virus)
Symptoms: Spinach infected with Cucumber
mosaic virus (CMV) will exhibit mottling on new
leaves. This mottling will develop into full leaf
chlorosis that is accompanied by leaf curling and
1. This document is PDMG-V3-48, one of a series of the 2006 Florida Plant Disease Management Guide, Department of Plant Pathology, Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date reviewed: January 2006. Please visit the EDIS Web site at
2. R. Raid, professor, Plant Pathology Department, Everglades Research and Education Center--Belle Glade, FL; T.A. Kucharek, professor, Plant Pathology
Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and
other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex,
sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry
2006 Florida Plant Disease Management Guide: Spinach 2
distortion. Leaf and plant death can occur. Stunting
can be quite apparent if plants are infected at an early
This virus infects plants in at least 34 plant
families that include such economically important
crops as cucumber, squash, pepper, turnip,
muskmelon, watermelon, eggplant, tobacco and
carrot. Many weeds also host this virus, especially
dayflower, Commelina spp. Aphids carry and spread
Cultural Controls: Plant varieties with tolerance
or resistance to CMV. Pursue perennial weed control
to prevent reservoirs of this virus near fields.
Stemphylium Leaf Spot (Stemphylium
Symptoms: Stemphylium leaf spot was first
reported in California in 1997, and appears to have
become endemic. Foliar symptoms were first
observed in Florida during the 2000-2001 growing
season, although the fungus had been previously
reported as a seed mold. Left uncontrolled, the
disease may result in significant losses, particularly in
spinach that is densely planted for the newly popular
"spring salad mixtures"
The disease starts out as small circular,
gray-green leaf spots, approximately 2-5 mm in
diameter. Visual symptoms appear about one week
following exposure to the pathogen. As the disorder
progresses, lesions expand, and coalesce, covering
larger portions of tissue. Seven to ten days after their
initial appearance, diseased foliar tissues turn light tan
to brown, and become papery in texture. Asexual
spores conidiaa) are dark brown, oblong with
rounded ends, and have both longitudinal and
transverse cross walls. Borne singly on typically
unbranched conidiophores with a swollen tip, conidia
may be viewed microscopically on the surface of
older lesions. However, sporulation is not readily
apparent to the naked eye, as with spinach downy
mildew and white rust.
Although infection may take place over a
relatively wide-range of temperatures, the disease is
favored by moderate to warm temperatures (18 to
240 C) and prolonged periods of leaf wetness.
Spores are disseminated by wind, rain splash,
irrigation, and farm implements or workers. Primary
inoculum is thought to originate from infested seed
or crop debris in or near the field.
Cultural Controls: There does not appear to be a
wide range in cultivar resistance to Stemphylium
botryosum at the present time. California research
showed only slightly less favorable lesion
development on the savoy spinach cultivar
"Vienna" than on other types or varieties tested.
Favored by free moisture, cultural practices that
promote unnecessary periods of leaf wetness, i.e.
overhead irrigation, should be avoided as much as
Chemical Control: Fungicides may be useful in
slowing or lessening the impact of the disease. Of the
currently registered fungicides, strobilurin
compounds appear to offer the most efficacious
control. To avoid possible phytotoxicity, care should
be exercised to read the specific label regarding their
use or mixture with other pesticides or adjutants,
particularly during warmer weather. See PPP-6.
White Rust (Albugo occidentalis)
Symptoms: Infected plants exhibit white,
blister-like pustules on the leaves, mostly on the
lower surface and petioles. Pustules are about 1/8
inch in diameter and can be solitary or grouped.
Leaves with numerous infections will discolor and
brown. The fungus can survive in crop debris as
sexual spores for about a year. The fungus is also
hosted by the weed relative, Chenopodium capitatum,
which is not known to occur in Florida at this time.
Other close weed relatives of spinach can exhibit a
similar white rust disease but the pathogen in these
situations does not infect spinach.
Cultural Controls: Crop rotation is advised
where the disease becomes established. All weed
species of Chenopodium should be eradicated since
their role in harboring the spinach white rust fungus
is unknown. The varieties Wintergarden, Jewel, and
Crystal have resistance to this disease.
Chemical Controls: See PPP-6.