Gladiolus Rust: A New Threat	

Background

Gladiolus rust (GR), a plant 

disease of quarantine 

significance, was detected and 

confirmed for the first time in 

the United States in April 2006 

on a gladiolus production farm 

in Manatee County, FL. The 

disease was later found on 

another commercial gladiolus 

farm in Hendry County, FL. In 

May 2006, GR was detected 

at one commercial and three 

residential sites in San Diego 

County, CA, just north of the 

Mexican border. State and 

Federal officials destroyed the 

infected plants and placed stop 

sale notices on the facilities.

The Center for Plant Health 

Science and Technology—part 

of the U.S. Department of 

Agriculture’s (USDA) Animal and 

Plant Health Inspection Service 

(APHIS)—organized a technical 

committee to devise appropriate 

eradication techniques specific 

to the infested areas of Florida 

and California. Although the 

Pest Alert Plant Protection and Quarantine

February 2007

specific source of the 2006 

infections is not known, in recent 

years, GR has been intercepted 

many times on cut gladiolus 

flowers entering the country 

as commercial shipments 

and/or in passenger baggage 

from Mexico, Brazil, and other 

countries.

Causal Agent

The fungus Uromyces 

transversalis Thum. causes 

GR only in the members of 

the family Iridaceae, including 

Gladiolus, Tritonia, Crocosmia, 

and Watsonia spp. Severely 

damaged plants do not flower 

and/or their corms do not 

ripen. The disease is serious in 

nurseries and can completely 

destroy commercial gladiolus 

crops unless fungicides are used.

Origin

GR is indigenous to southern 

Africa, where it was first noted 

on leaves of Tritonia securigera in 

1876. U. transversalis remained 

on the African continent until 

it reached the shores of the 

Mediterranean and spread 

to southern Europe almost a 

century later. The fungus was 

reported from southern France 

and northern Italy in 1966, from 

Malta in 1969, and from Morocco 

and southern Italy in 1977. U. 

transversalis had also spread to 

western France and England by 

1996, where it is an aggressive 

pathogen of commercial gladioli.

Transmission

Plants and cut flowers are the 

primary pathways for the introduction of GR. Its local 

spread occurs mainly by 

airborne spores, which are 

produced in prolific quantities 

on aboveground portions of 

the plant, especially on leaves, 

and disperse easily by wind 

or by lightly brushing the 

plants. Spores can travel long 

distances by wind or through 

the movement of cut flowers. 

GR spores can also be spread 

Figure 1—Healthy gladiolus leaves. Figure 2—Gladiolus leaves severely infected with gladiolus rust.
by surface-contaminated 

corms, rhizomes, and flowers. 

Interceptions from commercial 

shipments and passenger 

baggage at ports-of-entry in 

Arizona, California, and Texas 

confirm that cut flowers are the 

major pathway bringing GR into 

the country from Mexico and 

other countries.

Symptoms and

Identification

The presence of GR is 

determined by inspecting the 

leaves and stem of a plant. 

Symptoms are easily recognized 

as “typical rust” with orange sori 

(small blisterlike elevations of 

epidermis formed when spores 

have emerged) or pustules on 

both sides of the leaves. In U. 

transversalis, pustules tend to 

be elongated across the width of 

veins of a leaf and contain many 

spores.

The first symptoms of GR are 

small, yellowish spots. Later, 

the epidermis breaks down, 

exposing the pustules full of 

yellowish-orange spores and 

measuring 1 mm x 1 cm. Eventually, the pustules coalesce and 

form larger patches of damaged 

tissue. 

Disease Management

Fungicides can control GR, and 

for severe infections, weekly 

applications of bitertanol or 

triadimefon may be necessary 

to achieve a marketable yield of 

flowers. Systemic fungicides 

such as benodanil and 

oxycarboxin, sprayed weekly 

starting soon after emergence, 

provide good control.

Mexican government officials 

who recommend technical 

procedures for GR management 

stress that prevention is key. 

A recommended preventative 

control strategy is to combine a 

contact product (e.g., mancozeb) 

with a systemic fungicide (e.g., 

tebuconazole), thus providing 

the host plant with external and 

internal protection against rust.

For More Information

To learn more about gladiolus 

rust (GR), and/or if you see this 

disease, please contact USDA–

APHIS at (301) 734–4313.

The U.S. Department of 

Agriculture is an equal 

opportunity provider and 

employer.

This publication reports research 

involving pesticides. All uses of 

pesticides must be registered by 

appropriate State and/or Federal 

agencies before they can be 

recommended.

CAUTION: Pesticides can be 

injurious to humans, domestic 

animals, desirable plants, and 

fish or other wildlife—if they are 

not handled or applied properly. 

Use all pesticides selectively and 

carefully. Follow recommended 

practices for the disposal of 

surplus pesticides and pesticide 

containers.

Photo credits: All images were 

taken by APHIS plant pathologist 

Kimberly A. Schwartzburg.

United States

Department of Agriculture

Animal and Plant Health 

Inspection Service

APHIS 81–35–011

Figure 3—Inspecting young gladiolus plants for GR. Figure 4—Gladiolus plants ready for cutting.