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- Author or Editor: Larry K. Binning x
Abstract
Cuscuta spp. (dodder) are phanerogamic holoparasites. Swamp dodder (C. gronovii Willd. ex R. & S.) is a problem weed in cranberry (Vaccinium macrocarpon Ait.) in Wisconsin and Massachusetts, causing yield losses as high as 80% to 100% (Devlin and Deubert, 1980). At rates used in cranberry, the registered herbicides, granular chlorpropham (1-methylethyl 3-chlorophenylcarba-mate) and granular dichlobenil (2,6-dichlorobenzonitrile), are not totally effective, causing a steady increase in swamp dodder infestation. Since chlorpropham use was discontinued in 1988, dichlobenil is the only registered herbicide for dodder control in cranberry. The objective of this research was to investigate preemergence herbicides for swamp dodder control in cranberry.
Absorption of “C-labeled glyphosate by whole carrot (Daucus carota L.) plants infected or not infected by swamp dodder (Cuscuta gronovii Willd ex R & S) increased from 14% 1 day after treatment to 56% 14 days after treatment. Absorption of 14C-labeled glyphosate did not increase from 14 to 45 days after treatment. 14Carbon-labeled glyphosate appeared in the carrot root 1 day after application and its concentration increased with time in both infected and noninfected plants until 14 days after treatment. From 14 to 45 days after treatment, the concentration of 14C-labeled glyphosate in the roots decreased. At 1 day after treatment, dodder tissue contained as much 14C-labeled glyphosate as any physiological sink in the carrot. At 45 days after treatment, dodder tissue contained more 14C-labeled glyphosate than all other physiological sinks, except the petiole of the treated leaf. Swamp dodder stems had absorbed 14C-labeled glyphosate directly from a solution within 1 day after treatment. Chemical name used: N-(phosphonomethyl)glycine (glyphosphate).
Abstract
A simple model that predicts the onset of swamp dodder (Cuscuta gronovii Willd. ex R. & S. # CVCGR) emergence was developed. The use of growing degree days (GDD) with low-temperature thresholds (LTT) of 3.3° or 0°C had a better fit as a predictor for the beginning of emergence than either air temperature or soil temperature at a depth of 30 mm alone. This model can be used to time preemergence herbicide applications to coincide with the period of maximum dodder sensitivity, thereby increasing herbicide efficacy.