First Report of Gladiolus Rust Caused by Uromyces transversalis in Michoacán, México.

During October 2005, rust lesions were observed on leaves of gladiolus (Gladiolus sp.) plants being grown for flower production in a 20-ha field in eastern Michoacán, México. Disease incidence was near 100% in the field. Five symptomatic plants were collected on 11 and 25 October 2005, from each of 10 farms for further examination. Uredinia were scattered, orange, elliptical to irregular, and arranged transversely across the leaf. The sori were covered by the epidermis initially and later were erumpent and pulverulent. Urediniospores were bright yellow gold, ovate to oblong, and measured 15 × 19 µm (average). The urediniospore wall was hyaline and minutely echinulate. Telia were scattered, dark brown, elliptical, arranged transversely across the leaf, and were covered by the epidermis. Teliospores were irregularly pyriform, ovate, irregular or angular, light to dark brown with a conical or truncate apex and measured 17 × 23 µm (average). The teliospore wall measured 1 µm (average) thick at the sides and 3 µm (average) thick at the apex. Pedicels were light yellow and measured as much as 60 × 3 µm (average). On the basis of these characters, the rust was identified as Uromyces transversalis (Thüm.) G. Winter (1). To our knowledge this is the first report of U. transversalis causing gladiolus rust in Michoacán, México. Originally reported from Africa, the disease has been reported from Argentina, Brazil, southern Europe, and Oceania (1). Gladiolus rust caused by Uromyces transversalis is a quarantine disease for Europe and the United States. There have been unpublished reports of interceptions of this rust on cut flowers of gladiolus going from México into the United States (1). References: (1) J. R. Hernández. Invasive Fungi. Gladiolus Rust. Systematic Botany and Mycology Laboratory, Online publication. ARS, USDA, 2004.

First Report of Ovulariopsis on Lupinus havardii.

In 1998 and 1999 a severe powdery mildew was observed in Las Cruces, NM, on Big Bend Bluebonnets (Lupinus havardii) grown in the greenhouse for cut flowers and vase life studies. An undescribed powdery mildew has been reported on L. havardii (2), but it has been observed only occasionally on leaves and has not cause a severe problem. The powdery mildew observed in Las Cruces began in March and caused severe infection from May through July. The disease spread rapidly due to movement of the pathogen during pruning operations and the close proximity of plants. Plants were heavily infected when no fungicide was applied. Plants were sprayed with the fungicide azoxystrobin, with best control obtained at 687 mg/liter of water. When an infected plant was used as a source of inoculum, disease spread rapidly to healthy plants placed around the infected plant. Infected leaves had chlorotic lesions that later became necrotic. Mycelia, conidiophores, and conidia of the pathogen were observed on leaves and occasionally on petioles and stems. Ellipsoid cylindrical-to-clavate conidia were hyaline, one-celled, and measured 49 to 68.1 µm × 12.2 to 14.7 µm. Conidia were produced on upright, simple conidiophores measuring 171 to 245 µm × 4.9 to 7.3 µm. Fibrosin bodies and cleistothecia were not found. The fungus was identified as an Ovulariopsis sp. (1). This is the first documented report of an Ovulariopsis sp. on L. havardii. References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) W. A. Mackay and T. D. Davis. HortScience 33:348, 1998.

First Report of Pythium paroecandrum on Lupinus havardii.

Lupinus havardii Wats. (Big Bend Bluebonnet), a plant native to Texas, has been tested extensively for greenhouse production as a cutflower crop (1). Disease symptoms were observed on L. havardii plants grown in Las Cruces, NM, during two consecutive years. Plants were grown in Metro Mix 200 and watered by an automatic irrigation system every 3 days. During the growing season, which extended from September through February, 6% of mature plants (10-week-old plants) became chlorotic, wilted, and died. The first symptoms were observed during December 1998, when greenhouse temperatures were from 10 to 13°C. During the rest of the growing season, from February to July, only one plant became diseased, during May 1999, and the plant died within 1 week after greenhouse temperatures reached 20 to 25°C. Diseased plants were examined, and root, crown, and stem rot were found. Pythium paroecandrum Drechs. (2) was isolated routinely from infected tissues. Koch's postulates were fulfilled after plants were inoculated with oospores and mycelia of P. paroecandrum. Inoculum was applied next to the crown of 6-week-old plants in the form of water-agar plugs and a suspension that contained P. paroecandrum oospores and mycelia. Plants were maintained at 20 to 25°C. After 10 days, symptoms were similar to those previously observed, and the pathogen was reisolated from necrotic lesions observed on stems and crowns. Disease developed slower on 6-week-old plants (inoculated) than on 10-week-old plants (naturally infected). This is the first report of P. paroecandrum on L. havardii. References: (1) W. A. Mackay and T. D. Davis. HortScience 33:348, 1998. (2) A. J. Van der Plaats-Niterink. Monograph of the genus Pythium. Studies Mycol. 21:1, 1981.