Herbicides Applied to Dodder (Cuscutaspp.) after Attachment to Alfalfa (Medicago sativa)

Abstract

When glyphosate [N-(phosphonomethyl)glycine] at 0.075 kg/ha, DCPA (dimethyl tetrachloroterephthalate) at 10 kg/ha, and H 26905 [O-ethyl-O-(3-methyl-6-nitrophenyl)-N-sec-butyl phosphorothioamidate] at 0.25 and 0.5 kg/ha were sprayed on foliage of alfalfa (Medicago sativaL. ‘Vernal’) on which field dodder (Cuscuta campestrisYunck.) and largeseed dodder (Cuscuta indecoraChoisy) were attached and growing vigorously, almost all visible dodder tissue was killed and alfalfa was not injured noticeably. Some dodder recovered from haustoria within the alfalfa stems and from remnants of twined tendrils, but devastation of the alfalfa by uncontrolled dodder was prevented. PP 009 (butyl 2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy] propionate), BAS 9052 (2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one) and RO 13-8895 (acetone-O-[D-2-[p-[(α,α,α-trifluoro-p-tolyl)-oxy] phenoxy] propionyl] oxime) at 0.25, 0.50, or 1.0 kg/ha did not control dodder.

Effects ofAlternaria destruens, Glyphosate, and Ammonium Sulfate Individually and Integrated for Control of Dodder (Cuscuta pentagona)

“…Dodder treated with glyphosate alone regrew with vegetative tissue that was severely distorted and stunted. This has been observed in other studies where glyphosate alone was used to control dodder (Dawson and Saghir 1983). Glyphosate, which is translocated apoplastically and symplastically, has been reported to accumulate in dodder tissue because the parasite acts like a ''super-sink'' (Bewick et al 1991;Fer 1984).…”

“…The primary mode of action of glyphosate is the inhibition of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS; EC 2.5.1.19) in the shikimate pathway. Previous studies with glyphosate sprayed over the top of dodder-parasitized alfalfa resulted in injury and death to the field dodder with minimal to no injury to the alfalfa (Dawson 1990a,b;Dawson and Saghir 1983). Glyphosate applied at 75 or 150 g ae/ha during the eight-trifoliate leaf stage to the prebud stage provided only moderate or temporary injury to the alfalfa, but proved lethal to dodder (Dawson and Saghir 1983).…”

“…Previous studies with glyphosate sprayed over the top of dodder-parasitized alfalfa resulted in injury and death to the field dodder with minimal to no injury to the alfalfa (Dawson 1990a,b;Dawson and Saghir 1983). Glyphosate applied at 75 or 150 g ae/ha during the eight-trifoliate leaf stage to the prebud stage provided only moderate or temporary injury to the alfalfa, but proved lethal to dodder (Dawson and Saghir 1983). Although all exposed dodder shoots were killed by glyphosate, some haustoria were still embedded within the alfalfa stems and regenerated (Dawson 1990a).…”

Long‐distance transport of mRNA via parenchyma cells and phloem across the host–parasite junction in Cuscuta

“…These plants establish a connection with their host by growth of haustorial structures. The haustorium is used to connect the parasite vascular system to the host vascular system, allowing transfer of the vascular contents from the host to the parasite (Dawson et al, 1994). Consequently, parasitism retards normal plant growth and causes substantial crop losses in many economically important crops in both the developed and the developing world (Dawson et al, 1994).…”

“…The establishment of this interaction involves the formation of intricate connections between the parasite and its host (Dorr, 1996;Vaughn, 2003). Such interspecific plasmodesmata have been observed in root parasites such as Striga and Orobanche (Dorr & Kollmann, 1995;Dorr, 1996) as well as in the obligate parasite Cuscuta (dodder) (Dawson et al, 1994;Vaughn, 2003), and allow the parasite access to the symplastic contents of the hosts.…”