Plant Protection and Quarantine Pest Alert February 2007

Gladiolus Rust: A New Threat

Figure 1—Healthy gladiolus leaves. Figure 2—Gladiolus leaves severely infected with gladiolus rust.

Background specific source of the 2006 on the African continent until infections is not known, in recent it reached the shores of the Gladiolus rust (GR), a plant years, GR has been intercepted Mediterranean and spread disease of quarantine many times on cut gladiolus to southern Europe almost a significance, was detected and flowers entering the country century later. The fungus was confirmed for the first time in as commercial shipments reported from southern France the United States in April 2006 and/or in passenger baggage and northern Italy in 1966, from on a gladiolus production farm from Mexico, Brazil, and other Malta in 1969, and from Morocco in Manatee County, FL. The countries. and southern Italy in 1977. U. disease was later found on transversalis had also spread to another commercial gladiolus Causal Agent western France and England by farm in Hendry County, FL. In 1996, where it is an aggressive May 2006, GR was detected The fungus Uromyces pathogen of commercial gladioli. at one commercial and three transversalis Thum. causes residential sites in San Diego GR only in the members of Transmission County, CA, just north of the the family Iridaceae, including Mexican border. State and Gladiolus, Tritonia, Crocosmia, Plants and cut flowers are the Federal officials destroyed the and Watsonia spp. Severely primary pathways for the intro- infected plants and placed stop damaged plants do not flower duction of GR. Its local sale notices on the facilities. and/or their corms do not spread occurs mainly by The Center for Plant Health ripen. The disease is serious in airborne spores, which are Science and Technology—part nurseries and can completely produced in prolific quantities of the U.S. Department of destroy commercial gladiolus on aboveground portions of Agriculture’s (USDA) Animal and crops unless fungicides are used. the plant, especially on leaves, Plant Health Inspection Service and disperse easily by wind (APHIS)—organized a technical Origin or by lightly brushing the plants. Spores can travel long committee to devise appropriate GR is indigenous to southern distances by wind or through eradication techniques specific Africa, where it was first noted the movement of cut flowers. to the infested areas of Florida on leaves of Tritonia securigera in GR spores can also be spread and California. Although the 1876. U. transversalis remained Figure 3—Inspecting young gladiolus plants for GR. Figure 4—Gladiolus plants ready for cutting. by surface-contaminated Disease Management This publication reports research corms, rhizomes, and flowers. involving pesticides. All uses of Fungicides can control GR, and Interceptions from commercial pesticides must be registered by for severe infections, weekly shipments and passenger appropriate State and/or Federal applications of bitertanol or baggage at ports-of-entry in agencies before they can be triadimefon may be necessary Arizona, California, and Texas recommended. to achieve a marketable yield of confirm that cut flowers are the flowers. Systemic fungicides major pathway bringing GR into CAUTION: Pesticides can be such as benodanil and the country from Mexico and injurious to humans, domestic oxycarboxin, sprayed weekly other countries. animals, desirable plants, and starting soon after emergence, fish or other wildlife—if they are Symptoms and provide good control. not handled or applied properly. Identification Mexican government officials Use all pesticides selectively and who recommend technical The presence of GR is carefully. Follow recommended procedures for GR management determined by inspecting the practices for the disposal of stress that prevention is key. leaves and stem of a plant. surplus pesticides and pesticide A recommended preventative Symptoms are easily recognized containers. as “typical rust” with orange sori control strategy is to combine a contact product (e.g., mancozeb) (small blisterlike elevations of Photo credits: All images were with a systemic fungicide (e.g., epidermis formed when spores taken by APHIS plant pathologist tebuconazole), thus providing have emerged) or pustules on Kimberly A. Schwartzburg. both sides of the leaves. In U. the host plant with external and internal protection against rust. transversalis, pustules tend to United States be elongated across the width of For More Information Department of Agriculture veins of a leaf and contain many Animal and Plant Health spores. To learn more about gladiolus Inspection Service The first symptoms of GR are rust (GR), and/or if you see this small, yellowish spots. Later, disease, please contact USDA– APHIS 81–35–011 the epidermis breaks down, APHIS at (301) 734–4313. exposing the pustules full of yellowish-orange spores and The U.S. Department of measuring 1 mm x 1 cm. Event- Agriculture is an equal ually, the pustules coalesce and opportunity provider and form larger patches of damaged employer. tissue.