The Kerryman (South Kerry Edition)

Weed control in establishe­d grassland

AN INTEGRATED PEST MANAGEMENT PLAN IS CENTRAL TO SUSTAINABL­E CONTROLLIN­G WEEDS IN SWARDS

- By MATT O’SULLIVAN, TEAGASC ADVISER

GOOD grassland management is essential to sustainabl­e weed control in swards.

This should involve the adoption of an integrated pest management plan (IPM) approach, where cultural controls methods are considered before the use of pesticides.

Soil tests should be carried out to establish P and K levels; PH and the need for lime, as the ideal PH for grassland is 6.3.

If the soil PH, Phosphorus and Potassium are at optimum levels, more grass will grow and, as a result, limit space for weeds.

Poaching can damage or kill grass plants, and the bare ground is quickly replaced with weeds. Topping weeds before they go to seed and drainage of water-logged land are also important, integrated pest-management measures.

Remember land parcels selected for Glas action Low Input Permanent Pasture cannot be topped between March 15 and July 1 annually. In establishe­d and permanent grassland, the six most common weeds are docks, thistles nettles, chickweed, buttercup and ragwort.

Rushes can also be an issue and require annual management. Generally herbicides should be applied when weeds are actively growing, from seedling stage to just before flowering.

Docks should be sprayed when they are actively growing in the summer months, when they are free of disease, pest attack and drought.

For the herbicide to effective, it needs to be taken into actively growing leaves and transporte­d around the plant.

Once stem extension starts, leaf growth is insufficie­nt for the herbicide to work effectivel­y.

If the stem and seeds are present, top the weeds and spray the regrowth a few weeks later. Teagasc trials have shown that longer-term control of docks can be achieved by applying a suitable herbicide onto small docks shortly after reseeding.

By applying the herbicide at this stage of the docks’ developmen­t, it facilitate­s almost complete eliminatio­n of the dock.

The following year’s docks will fail to establish due to competitio­n from the grass.

In selection of herbicide for use in establishe­d grassland, ensure its applicatio­n does not kill off sward species such as clover.

Forefront T controls a wide range of weeds including thistles, nettles, docks, ragwort and buttercup, but it is not clover safe.

Grazing animals tend to avoid patches of weeds, especially thistles. As a result, ungrazed grass around weeds reduces pasture utilisatio­n. Weeds such as bracken, ragwort or hemlock pose a threat to livestock health.

Normally animals do not eat weeds in pastures unless grazing is extremely restricted. Controllin­g broadleave­d weeds in grassland will maximise grass yield, improve silage quality, increase pasture utilisatio­n and will eliminate health risks to livestock.

In weed control, apply approved products for the target weeds at the correct rate and stage of growth.

Don’t spray if heavy rain is forecast and adhere to buffer margins. Follow the recommenda­tions of Integrated Pest Management and use best practice guidelines in the applicatio­n of herbicides. Under the Sustainabl­e Use of Pesticides Directive (SUD) any person who uses pesticides must be registered as a Profession­al Pesticide User.

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