Poinsettia scab - Sphaceloma poinsettiae

During the summer of 2000 poinsettia scab or spot anthracnose caused by Sphaceloma poinsettiae was found on greenhouse-grown poinsettia plants that originated in Guatemala. The disease has been seen sporadically on plants grown from imported poinsettia cuttings in subsequent years. This disease results in plants with white to pale buff spots on leaves and bracts that make them unacceptable for sale.

Sphaceloma poinsettiae Jenk. & Ruehle

Spots on living leaves especially along veins and margins and on stems; forming raised, pale buff, circular to elongate spots with purple margins and often a yellow halo, 2-10 mm diam, sometimes causing in-rolling of leaves. Stroma mingled with host tissue, appearing as gray to olive-brown coating of hyaline to pale yellow hyphae forming a loose stroma. Conidiophores arising from stroma, 15-30 x 3-5 um, straight or curved, tapering to apex, usually continuous to 1-septate. Conidia 7-20 x 2.5-5.3 um, elliptical to oblong, continuous or 1-, rarely 2-septate, hyaline to pale yellow.

Hosts: Euphorbia pulcherrima Willd. ex Klotsch, rarely also reported on E. cyathophora Murray and E. heterophylla L. (Euphorbiaceae)

Geographic distribution: Originally described from FL, this fungus is known primarily from the Caribbean and reported from AZ, HI, LA, TX, Mexico Brazil, Fiji and the Republic of South Africa (Farr, et al. n.d.).

Sphaceloma poinsettiae is relatively common on Euphorbia pulcherrima in tropical regions. It is also reported on the cultivated plant E. cyathophora as well as E. heterophylla, a noxious weed commonly known as Mexican fireplant or painted euphorbia. Most cultivars of E. pucherrima including all bract colors appear to be susceptible, but some variation in the level of susceptibility has been noted.

Online References:

Benson, D.M. et al. 2002. Poinsettia: The Christmas Flower - APSnet Feature Story, December 2001/January 2002
Whipker, B.E. et al. 2000. Poinsettia: Poinsettia Scab (Spot Anthracnose) - N.C. State University Floriculture Research (PDF)

References:

C.M.I. 1986. Sphaceloma poinsettiae. Distrib. Maps Pl. Dis. 393: 1-2.

Daughtrey, M.L., Wick, R.L., and Peterson, J.L. 1995. Compendium of Flowering Potted Plant Diseases. APS Press, St. Paul, Minnesota, 90 pages.

Ruehle, G.D. 1941. Poinsettia scab caused by Sphaceloma. Phytopathology 31: 847-948.

Nomenclature

Specimens in BPI

Additional distribution data

Suggested citation: Rossman, A.Y., Palm, M.E., and Daughtry, M. Systematic Mycology and Microbiology Laboratory, ARS, USDA. 5 May 2005. Invasive Fungi. Poinsettia scab - Sphaceloma poinsettiae. Retrieved November 21, 2009, from http://nt.ars-grin.gov/sbmlweb/fungi/index.cfm .