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).
Uniformity of sand deposition on cranberry (Vaccinium macrocarpon) farms was examined to evaluate the potential use of two sanding methods to suppress swamp dodder (Cuscuta gronovii) seedling emergence by seed burial. During a 2-year study, 24 farms were evaluated with sand applied by either water barge or directly on ice. To measure the depth of sand deposited on the surface, soil cores were taken every 5 m in a grid pattern on a randomly selected portion of a commercial Massachusetts cranberry farm. Both application methods delivered nonuniform depositions of sand with the majority of the samples measuring less than the target depth. Surface diagrams depicting sand depths indicated no particular patterns of error or deposition that could be advantageously adjusted by the grower at the time of application. Mean actual: target depth ratios were 63% and 66% for barge and ice sanding, respectively (100% indicating actual equaled target). In the best scenario (two farms), 47% of the sanded area received less than the target amount; 11 farms had at least 90% of actual sand depths below the target depth. For farmers targeting 25-mm sand depths (depth expected to suppress dodder germination), the mean actual: target depth ratio was 58%, indicating half of the actual sand depths measured less than 15 mm. Compaction of the sand layer due to the elapsed time period (6 weeks or more) between sand application and measurement may have contributed to the large number of samples that were lower than the target depth. Even so, the irregularity of deposition patterns and the large proportion of sand depths that were less than 25 mm indicated adequate suppression of dodder seedling emergence would be unlikely with either sanding method.
Over a 2-year period, 11 cranberry (Vaccinium macrocarpon) farms in southeastern Massachusetts were selected to evaluate mechanical removal of swamp dodder (Cuscuta gronovii) with a conventional hand-held bamboo rake. This technique consisted of breaking and removing large strands of the parasite that connected host plants; embedded and encircled portions of the parasite were not removed. Differences in dodder biomass, cranberry yield, and berry weight were determined in plots that received zero, one, or two weed-removal events. Removing dodder one time per season reduced percentage of weed cover by more than 74% in both years. Impacts on dodder fresh and dry weight were not as discernible. Removal initially decreased dodder biomass, which remained 20% to 40% lower than the baseline values, but removal treatments did not differ statistically from the control. No additional benefits were obtained by removing the weed cover more than once. Biomass per berry was not affected by mechanical weed removal and fruit of marketable size were produced in the treated area. Substantial yield loss was largely attributable to the dodder infestations, but multiple removals may eventually reduce yield to levels below those associated with infestations alone.
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.
Field conditions associated with commercial cranberry (Vaccinium macrocarpon Ait.) production were simulated in greenhouse studies to determine the effect of soil surface characteristics on dichlobenil activity. Sand was compared with organic matter, in the form of leaf litter, as the surface layer. A seedling bioassay using alfalfa (Medicago sativa L.), a dichlobenil-sensitive plant, was employed to determine root growth response on herbicide-treated soil. When the herbicide was applied to a sand surface, root growth was greater as time after application elapsed, indicating loss of herbicide activity. Conversely, the presence of organic matter on the surface prolonged the activity of the herbicide. Composition of the surface layer was more important than the depth of the layer in determining herbicide persistence. The influence of cultural practices, such as the application of sand or the removal of surface debris, on herbicide activity should be considered when planning weed management strategies for cranberry production. Chemical name used: 2,6-dichlorobenzonitrile (dichlobenil).
A system of mapping weed infestations in cranberries (Vaccinium macrocarpon Ait.) was developed that enables growers to incorporate integrated pest management practices into their weed control program. This system provides growers with information on the location of weeds and the area of weed patches, but differs from other weed mapping systems in that information on control priorities is included on the maps. Weed management efforts can then be directed to the most economically damaging weeds first. The mapping system also provides growers with a permanent record that can be used to communicate with staff and to evaluate weed management strategies.
is periodically applied over cranberry vines during the dormant season to promote new shoot development and rooting ( Demoranville and Sandler, 2008 ). This technique has reduced the emergence of swamp dodder ( Cuscuta gronovii Willd. ex Schult
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