Arceuthobium blumeri A. Nelson (Blumer's dwarf mistletoe, Viscaceae) is a parasite of Pinus ayacahuite Ehrenberg ex Schlechtendahl (Mexican white pine) and P. strobiformis Engelm. (southwestern white pine) in the Sierra Madre Occidental of northern Mexico (3). It is widely distributed in Chihuahua and Durango and is known from one location in Sonora (3,4). A. globosum Hawksworth & Wiens subsp. globosum (rounded dwarf mistletoe) parasitizes several pine species in the same areas of Mexico, but extends as far south as northern Jalisco (3). In July 2005, S. Quiñonez Barraza observed both of these dwarf mistletoes in Ejido San José del Barranco, Municipio de Badiraguato, Sinaloa, Mexico. A. blumeri was observed parasitizing P. ayacahuite at two locations: Paraje Faldeo Rancho del Oso (25°39′18″N, 107°01′27″W, elevation 2,600 m) and Paraje La Tableta (25°40′14″N, 107°01′33″W, elevation 2,520 m). The host at these two locations was identified by cone and needle morphology (1). Because the mistletoe plants were gray to straw in color and larger than 6 cm, they were clearly A. blumeri and not A. apachecum Hawksworth & Wiens, another dwarf mistletoe that parasitizes P. strobiformis in Arizona, New Mexico, and Coahuila, Mexico (3). A. globosum subsp. globosum was observed parasitizing P. durangensis Martínez at Paraje Puerto del Alacrán (25°39′52″N, 107°00′57″W, elevation 2,650 m). Infection of the pine hosts was severe at all three locations in Sinaloa and many trees were rated as class 5 and 6 by the 6-class dwarf mistletoe rating system (2). Large witches' brooms were formed on P. ayacahuite infected with A. blumeri, but no witches' brooms were formed on infected P. durangensis. Typically, A. globosum does not induce witches' brooms on infected pines (3). Specimens of A. blumeri and A. globosum subsp. globosum were collected and deposited at the Herbario CIIDIR, Instituto Politecnico Nacional, Durango, Dgo., 34220 Mexico. To our knowledge, this is the first report of A. blumeri and A. globosum subsp. globosum from Sinaloa, Mexico.
References: (1) A. Farjon and B. T. Styles. Flora Neotrop. Monogr. 75. 1997. (2) F. G. Hawksworth. USDA For. Serv. Gen. Tech. Rep. RM-78, 1977. (3) F. G. Hawksworth and D. Wiens. USDA For. Serv. Agric. Handb. 709, 1996. (4) R. Mathiasen et al. Madroño 55:161, 2008.
