Response of Cuscuta campestris and Cuscuta indecora to glyphosate applied after attachment to alfalfa (Medicago sativa)

Graduation date: 1988The response to glyphosate [N-(phosphonomethyl) glycine] of two\ud dodder species Cuscuta campestris Yuncker (field dodder) and Cuscuta\ud indecora Chiosy (largeseed dodder) parasitizing alfalfa (Medicago\ud sativa L.) was compared. In the absence of glyphosate, alfalfa was\ud killed or severely injured by parasitism from uncontrolled dodder.\ud Results of field experiments in which glyphosate at 75 or 150 g/ha\ud was sprayed over the host and parasite showed that initial growth of\ud treated dodder, regardless of species, ceased within a few days\ud following application with no obvious injury to alfalfa. Although\ud initial measurements of response of individual variables varied\ud greatly, effect of glyphosate treatments did not show differences\ud between the two dodder species at this stage. Later, variations in\ud regrowth and condition of development were useful to show differences\ud between treated dodder species. The two species had similar injury\ud symptoms, but in Cuscuta campestris higher percentage of abnormal\ud tissue led to a lower survival rate. Throughout the experiments,\ud Cuscuta indecora stood out to be more tolerant than Cuscuta\ud campestris. Both field and greenhouse shoot-dip experiments\ud indicated that translocation and direct uptake are equally important\ud in post-attachment injury of dodder by glyphosate