Regulations (pertaining to the Great Lakes)
The Great Lakes Indian Fish & Wildlife Commission ranked R. obtusifolius as capable of low to moderate ecological impacts ,and does not consider it a priority for control within their ceded territories (Falcke and Garske 2003). There are no federal (or state within the Great Lakes region) regulations for this species. Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Biological
Bitter dock is avoided by rabbits, but it appeared to be a favorite food plant of deer (Amphlett and Rea 1909, cited in Cavers and Harper 1964). Docks are grazed by cattle, sheep, and goats, but not by horses.
Cavers and Harper (1964) list a range of fungi and insects that attack, feed on or occur on docks but this not an indication that of their efficacy as control agents. The use of the stem boring larvae of the weevilsApion violaceum and A. miniatum for controlling Rumex obtusifolius has been investigated (Hopkins, 1980; Freese, 1995). In the UK and elsewhere, there has been research on the chrysomelid beetle (Gastrophysa viridula) as a biocontrol agent for both R. obtusifolius and R. crispus (Bentley et al., 1980). Larvae of the leaf-mining fly Pegomya nigritarsis cause blotch mines on leaves of R. obtusifolius (Whittaker 1994). Rumex obtusifolius is the preferred host plant of Coreus marginatus and has been shown to moderately reduce its seed viability (Hruskova et al 2005). The leaf spot fungus Ramularia rubella causes red spots to develop on dock leaves, but has no major effect on plant survival. The rust fungus Uromyces rumicis is also non-systemic but has been shown to have some potential as a biological control agent (Inman, 1971; Schubiger et al., 1986). Dock species are also an alternate host for number of viruses, funguses (Dal Bello and Carranza 1995), and nematodes (Edwards and Taylor 1963, Townshend and Davidson 1962).
Physical
Caution should be used in physical removal, as this plant can cause contact dermatitis.
Repeated cultivation is recommended for control of young (seedling) populations.
Mowing has little effect on established docks, but will prevent seed production. However, frequent cutting encourages taproot growth, branching shoots and may aid seedling development (from previous year’s seed bank) and so is not recommended. In a pasture heavily infested with docks the best option may be to plough and reseed with grass but not immediately. The docks are likely to regenerate both vegetatively and from seed, and a period of fallowing or arable cropping may help to reduce re-establishment.
Chemical
Many chemical controls are available for dock species. However, very few are approved for use in or near water. Repeated treatments are usually needed to control re-growth.
Dicamba (benzoic acid) is effective on curly dock (Rumex crispus) but not on broadleaf dock (R. obtusifolius). Picloram (pyridine) is effective on most Rumex species. 2,4-DB amine or 2,4-D ester are effective when applied beforethe flower stalk elongates, but require a 30 day withdrawl before feeding as forage. Aminopyralid can be applied to actively growing plants before the bud stage. Chlorsulfuron and metsulfuron can be used with young, actively growing plants, but should not be used on powdery, dry, or light sandy soils. Sulfoteturon has similar use, but should not be applied to cropland. Glyphosate can be used at early heading (Pacific Northwest Extension 2013).
Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.