2,6-Dichlorobenzonitrile

Mechanism of action

It has herbicidal properties killing young seedlings of both monocot and dicot species. DCBN interferes with cellulose synthesis. DCBN adapted cell walls use minimal amounts of cellulose, instead relying on Ca2+-bridge pectates.

Dichlobenil kills the roots of many species, but not all; further, the killing does not extend much beyond the portion actually soaked, according to the Californian department of agriculture in 1971.

Application

In 1996, the University of California reported that "dosages were difficult to control... and as a result soaking or spraying methods are no longer used. ... The current application method involves applying metam-sodium products in foam carriers (similar to shaving cream)."

Environmental behavior

It has low solubility, is not highly volatile and has potential to leach into groundwater. It is moderately persistent in soils and very persistent in water. It is moderately toxic to mammals, aquatic organisms, honeybees and earthworms.

Dichlobenil residue in water almost completely dissipates in 5 to 6 months.

The USDOE Bonneville Power Administration reported "high potential" for dichlobenil to enter groundwater.

Regulatory status

It is no longer approved for use within the EU, as of 2009.

The Inland Fisheries Ireland has reported "the registration of all dichlobenil products ... was revoked in Ireland from 18th March 2009, under Commission Decision 2008/754/EC of 18th September 2008. A period of grace for ... existing stocks expired on 18th March 2010." The London underground found itself in violation by using dichlobenil in September 2011.{{cite news | title = 'Toxic' pesticide Dichlobenil used on London Underground | publisher = BBC News

Environmental toxicity

On an acute basis, dichlobenil is practically nontoxic to birds, mammals, honey bees; slightly to moderately toxic to aquatic invertebrates and estuarine organisms; and moderately toxic to fish. Dichlobenil is practically nontoxic to birds on a subacute dietary basis, but insufficient data are available to assess chronic avian toxicity. Dichlobenil is toxic to non-target terrestrial and aquatic plants. Dichlobenil may chronically affect fish at levels as low as 0.33 ppm and may chronically affect aquatic invertebrates at levels as low as 0.75 ppm. The dichlobenil degradate, BAM is slightly toxic to mammals and practically nontoxic to fish and aquatic invertebrates on an acute basis.

Safety

Since 1995, the U.S. National Institutes of Health has warned about indoor usage: "Leave all windows open and fans operating... Put all pets outdoors, and take yourself any your family away from treated areas for at least the length of time prescribed on the label."

The UN IPCS reports dichlobenil can be absorbed into the body by inhalation, through skin and by ingestion, and that dispersion can create harmful concentrations in air quickly; dichlobenil may affect skin, possbily causing chloracne.{{cite web| title = dichlobenil (Ref: H 133)

The U.S. Centers for Disease Control and Prevention (CDC) follows and cites the ICPS.

Products

United States

These consumer products use dichlobenil as an active ingredient: "Oblitiroot", "Root Reach", "Foaming Root Killer" and "RootX". This is not an exhaustive list.

"Casoron" is dichlobenil sold agriculturally as a 50% wettable powder and as 4% granules.

Synthesis

Dichlobenil is produced from 2,6-dichlorotoluene via the aldoxime.

References

References

1. Franz Müller and Arnold P. Applebyki "Weed Control, 2. Individual Herbicides" in Ullmann's Encyclopedia of Industrial Chemistry 2010 {{doi. 10.1002/14356007.o28_o01
2. [https://books.google.com/books?id=iuNS1Yj09XYC&dq=Cirsium+arvense+dicot+control&pg=PA87 Principles of weed science]
3. [https://books.google.com/books?id=QOe9Qy6g4QsC&dq=Dichlorobenzonitrile+mechanism&pg=PA43 Plant Responses to Environmental Stresses: From Phytohormones to Genome Reorganization: From Phytohormones to Genome Reorganization]
4. (1971). "Control of Tree Roots in Sewers and Drains". California Agriculture.
5. (1996). "Control of Tree Roots in Sewers and Drains". University of California: Statewide Integrated Pest Management Project - Pesticide Education Program.
6. (2006). "dichlobenil (Ref: H 133)". University of Hertfordshire - Pesticide Properties DataBase.
7. "Lagarosiphon Control in Lough Corrib". Inland Fisheries Ireland.
8. "Dichlobenil: Herbicide Fact Sheet". U.S. Department of Energy - Bonneville Power Administration.
9. (October 1998). "Dichlobenil". [[US EPA]].
10. "Dichlobenil". NIH NLM ToxNet.
11. "Oblitiroot". Olvidium.
12. "Root Reach". Heartland Labs.
13. "Foaming Root Killer". Roebic.
14. "RootX". RootX.
15. (1974). "Effects of certain preemergence herbicides on Diochondra spp.". Proceedings of the Second International Turfgrass Research Conference.