Added in 2005 – Deleted in 2009 Reasons for deletion

Why The recent and rapid spread of Phakopsora pachyrhizi in the Americas attracted our attention. Although data is lacking on potential establishment in the Euro-Mediterranean region (tropical and sub-tropical pathogen), the EPPO Secretariat decided to add it to the EPPO Alert List.

Where Asia: Cambodia, China, India, Indonesia, Japan, Korea, Malaysia, Nepal, Philippines, Russia (Far East), Taiwan, Thailand, Vietnam.

Africa: Ghana, Mozambique, Nigeria, Rwanda, Sierra Leone, South Africa, Uganda, Zambia, Zimbabwe.

North America: Mexico (San Luis Potosi, Tamaulipas, Veracruz), USA (Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Hawaii, Louisiana, Mississippi, Missouri, Nebraska, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia).

South America: Argentina, Bolivia, Brazil (Goias, Maranhão, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Paraná, Rio Grande do Sul, São Paulo), Paraguay, Uruguay.

Oceania: Australia, Papua New Guinea.

On which plants Soybean (Glycine max) is the main cultivated host but many other Fabaceae can host this rust, for example: Lupinus hirsutus, Medicago arborea, Melilotus officinalis, Phaseolus vulgaris, P. lunatus, Vicia dasycarpa, Vigna unguiculata, and weeds such as: Desmodium tortuosum, Pueraria montana var. lobata (kudzu). More data is needed on the range and economic importance of P. pachyrhizi on legume hosts, other than soybean.

Damage The most common symptoms of infection by P. pachyrhizi are tan-to-dark brown or reddish brown lesions (2 to 5 mm²) which are usually clustered along the veins. Lesions contain erumpent, globose uredinia. Urediniospores are released through the circular ostiole. The disease begins with small, water-soaked lesions, which gradually increase in size, turning from grey to tan or brown. They assume a polygonal shape restricted by leaf veins and usually coalesce to form larger lesions. As the plant matures and sets pods, the symptoms spread rapidly to the middle and upper parts of the plant. Lesions are found on petioles, pods, and stems but are most abundant on leaves. As rust severity increases, premature defoliation and early maturation of plants is common. In areas where the pathogen occurs commonly, yield losses up to 80% have been reported. Successful infection is dependent on the availability of moisture on plant surfaces. At least 6 h of free moisture is needed for infection with maximum infections occurring with 10 to 12 h of free moisture. Temperatures between 15 and 28°C are ideal for infection.

Dissemination Over long distances, P. pachyrhizi is mainly spread by wind-borne spores (e.g. in USA, it is considered that Hurricane Ivan transported it from South America to Southern USA, see Internet animation https://netfiles.uiuc.edu/ariatti/www/SBR/Ivan.htm). Trade of host plants cannot be excluded as a pathway (e.g. leafy vegetables, ornamentals, pods).

Pathway Plants for planting, ornamental cut foliage, vegetables of host plants may ensure dissemination of the pathogen.

Possible risks Soybean is an important crop in the EPPO region. P. pachyrhizi is considered as a serious rust disease in countries where it occurs. Control methods are available (chemical control, destruction of weed hosts) but more data is needed on their efficacy. Preliminary CLIMEX studies have showed that low winter temperatures and lack of humidity are limiting factors for the establishment of the pathogen, and therefore in Europe, only Southern Mediterranean countries may be at risk. However, more detailed studies on its potential for establishment would be needed for the EPPO region.

Source(s) Gupta VP, Kaur A (2004) Phakopsora pachyrhizi – soybean rust pathogen new to Rajasthan. Journal of Mycology and Plant Pathology 34(1), p 151 (abst.).

Klag N (2005) Soybean Rust. NAPPO Newsletter, March, p 4.

Lynch TN, Marois JJ, Wright DL, Harmon PF, Harmon CL, Miles MR (2006) First report of soybean rust caused by Phakopsora pachyrhizi on Phaseolus spp. in the United States. Plant Disease 90(7), p 970.

Pivonia S, Yang XB (2004) Assessment of the potential year-round establishment of soybean rust throughout the World. Plant Disease, 88(5), 523-529.

Sconyers LE, Kemerait RC Jr, Brock JH, Gitaitis RD, Sanders FH, Phillips DV, Jost PH (2006) First report of Phakopsora pachyrhizi, the causal agent of soybean rust, on beggarweed in the United States. Plant Disease 90(7), p 972.

Yorinori JT, Nunes Junior J, Lazzarotta JJ (2004) [Asiatic rust of soyabeans in Brazil: evolution, economic importance and control.] Documentos – Embrapa Soja no. 247, 63 pp (abst.).

INTERNET

NAPPO Pest Alert System - Official Pest Reports (2006-02-16) Detection of soybean rust (Phakopsora pachyrhizi) in the states of Tamaulipas and San Luis Potosi, Mexico. http://www.pestalert.org/oprDetail.cfm?oprID=192

NAPPO Pest Alert System. Official Pest Reports (2007-07-12) Detection of Asian soybean rust (Phakopsora pachyrhizi) in yam bean crops in Papantla, Veracruz, Mexico. http://www.pestalert.org/oprDetail_print.cfm?oprid=267

ProMed postings. http://www.promedmail.org

Soybean rust – USA: 1^st report (2004-11)

Soybean rust, Asian strain – Arkansas: 1^st report (2004-11).

Soybean rust, Asian strain - Brazil (2004-12).

Soybean rust, Asian strain – Argentina (2005-01).

Soybean rust, Asian strain – USA (Florida) : 1^st report 2005 (2005-03).

Soybean rust – Mexico (02) (2006-05-25)

Purdue University. Plant and Pest Diagnostic Laboratory. Asian soybean rust. Phakopsora pachyrhizi. http://www.ppdl.purdue.edu/PPDL/soybean_rust.html

USDA-APHIS. Pest Alert. Soybean Rust. http://www.aphis.usda.gov/ppq/ep/soybean_rust/

USDA Soybean rust information site. http://www.sbrusa.net/

USDA – Integrated Pest Management – Pest Information Platform for Extension and Education. http://www.sbrusa.net/cgi-bin/sbr/public.cgi

Plant Management Network. Soybean Rust. http://www.plantmanagementnetwork.org/infocenter/topic/soybeanrust/

EPPO RS 2005/029, 2006/076, 2006/200, 2006/230, 2007/187, 2008/057