Why timing is vital when treating rushes

Licking method, using a tractor or quad, has the advantage of being applied primarily to the target plant - rushes or other tall weeds.
Licking method, using a tractor or quad, has the advantage of being applied primarily to the target plant - rushes or other tall weeds.

Conor Dowling

If you are considering spraying rushes timing is everything.

Protection of the environment is more important than ever since these chemicals have been found in drinking water supplies.

A young actively growing rush about 15cm should be targeted. These plants occur early in the growing season or 4-6 weeks after a mature plant has been cut.

When the plant is young the skin is less waxy and this allows the chemical product to enter more easily, a sticking agent will also help this process.

Also when the plant is actively growing the chemical product can move around in the plant and disrupt its growth. If topping or cutting of the rushes is needed then cuttings should be removed from the field as they can create bare patches and provide a seed bank for future infestations.

The main chemicals licensed for rush control in grassland are MCPA and Glyphosate. These chemicals are the active ingredients and are sold under various brand names.

MCPA can only be applied by a boom sprayer and that boom sprayer used must be certified and the operator must have a Professional User number.

Glyphosate is a non-selective herbicide, that means it kills any plant material it comes in contact with. It is the only product licensed for use in a weed wiper/licker. A difference in height is needed between the rush and the surrounding grass so tight grazing may be needed before treatment. When a product to treat rushes is chosen, always read and follow the label.

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The label will outline how the operator can use the product legally. The method of application, the concentration, the crops the product can be applied to along with the buffer zone for each product will be on the label. MCPA is highly soluble in water and accounts for the majority of pesticide breeches of drinking water standards.

The buffer zone for MCPA is 5m (Do not spray within 5m of a water body) and can only be used in the months of March to September.  If you are in GLAS then the treatment of rushes in LIPP or THM is only spot spraying or weed licking.

Therefore, the only legal method to treat the rushes is by weed licking with Glyphosate. After treatment is complete records of application should be updated.

Conor Dowling, Teagasc Soils and Environment Adviser, Castlerea

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