The Honduran dwarf mistletoe, Arceuthobium hondurense Hawksw. & Wiens (Viscaceae), is one of the rarest dwarf mistletoes known in Central America (1,2). It is only known from four general areas in Honduras, but has also been reported from three locations in southern Mexico (2,3). At one time, A. hondurense was thought to be in danger of extinction (1). During March 2006, we found three new populations of this rare dwarf mistletoe in the Cordillera Dipilto in northern Nicaragua (Department Nueva Segovia). One population was approximately 11 km northeast of San Fernando (13°44′55″N, 86°19′07″W; elevation 1,130 m), the second population was approximately 9 km north of Mozonte (13°44′09″N, 86°24′54″W; elevation 1,415 m), and the third population was approximately 6 km southwest of Depilto (13°42′51″N, 86°32′22″W; elevation 1,340 m). Honduran dwarf mistletoe was parasitizing Pinus tecunumanii Equiluz & J.P. Perry at each of these locations, and at the Mozonte population, it was also infecting P. oocarpa Schiede ex Schlecht. Only a few pines were infected at each of these localities and no pine mortality associated with dwarf mistletoe infection was observed. However, even lightly infected trees had large witches' brooms and some trees were severely broomed. These populations are 50 to 65 km southeast of the nearest population of Honduran dwarf mistletoe in Honduras and they represent the southern most populations of Arceuthobium spp. in the New World (1). The mistletoe, Struthanthus deppeanus (Cham. & Schlecht.) Bl. (Loranthaceae), also parasitizes pines in Central America and southern Mexico (3). We observed this mistletoe parasitizing P. tecunumanii at the San Fernando location described above, on P. oocarpa approximately 7 km north of Mozonte (13°43′57″N, 86°24′49″W; elevation 1,490 m), and on P. oocarpa approximately 3 km southwest of Dipilto (13°43′40″N, 86°31′56″W; elevation 1,170 m). Again, only a few pines were infected at each of these locations, and we did not observe pine mortality associated with infection by S. deppeanus. S. deppeanus does not cause the formation of witches' brooms on infected pines, but the mistletoe plants are often greater than 1 m long so they are easily observed. This mistletoe was most common southwest of Depilto. To our knowledge, this is the first report of A. hondurense and S. deppeanus in Nicaragua. Specimens of A. hondurense and S. deppeanus from Nicaragua have been deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff (Accession Nos. 81561--81567).
References: (1) F. Hawksworth and D. Wiens. Dwarf mistletoes: Biology, pathology, and systematics. USDA For. Serv. Agric. Handb. 709, 1996; (2) R. Mathiasen and J. Melgar, Plant Disease 90:685, 2006; (3) R. Mathiasen et al. Madrono 50:115, 2003.
