The genus Cuscuta (dodder) consists of approximately 170 species of obligate holoparasitic plants distributed throughout the world. Several species are found in Guam and the neighboring islands that commonly infest trees, shrubs, and herbaceous plants. Field and greenhouse experiments were conducted in 2005 and 2006 in Guam to evaluate the effects of glyphosate on field dodder control, and to describe glyphosate dose response curves on selected ornamental plants grown with and without dodder infestation. Visual quality of dodder-free plants decreased with increasing dose of glyphosate but the magnitude of the decrease varied among plant species. The most sensitive species was king's mantle while the most tolerant was hibiscus. The values for ED10 dose of glyphsoate (10% reduction in visual quality) were 800, 280, 1250, 370, 590, 830, 660 and 170 g ai ha-1 for dodder-free: croton, allamanda, hibiscus, paper gardenia, ixora, duranta, schefflera, king's mantle, respectively. However, dodder-infested plants were less tolerant to glyphosate due to the confounded stress from both the parasite and herbicide. Field dodder parasitizing ornamental plants could be adequately controlled on all ornamental species at dose of about 140 g ha-1 of glyphosate.