Six of Your Weed Control Questions Answered by Teagasc.

(1) In late summer, when is the best time to spray for docks in grassland?

Spray docks when they are actively growing in the summer months when they are free of disease, pest attack, drought, etc. with nutrients being translocated to leaves, stem and roots of the actively growing dock plant.

Best time to spray is before stem formation. In late July, this is when the dock plant has plenty of leaves to absorb chemicals in herbicide being used.

If stem and seeds are present on dock plants, it may be best to top the field, then spray the regrowth a few weeks later.

(2) In a field with peaty soil, furze bushes on the boundaries have started to grow out into the field. I am afraid that I may be penalised if I have a Cross Compliance inspection. So what is the best way to control these furze bushes?

Yes, you could be penalised if you have a Cross Compliance inspection.

That is if you allow this invasive species to continue to grow out into the field. Very few herbicides will kill hard, woody stem material.

Best suggested practice is to cut any growing bush at the butt at ground level using a small chainsaw.

After a few weeks, any regrowth can be spot sprayed with Grazon 90 at the recommended rate.

(3) Creeping buttercup has started to emerge in some low lying fields that I own. How can I control this?

Buttercups are best controlled by MCPA or 2, 4-D or Lupo. Check each field to see what weeds you need to deal with before spraying and select the best spray to deal with all the weeds.

(4) I have a persistent problem with creeping thistle in many of my fields, what is the best herbicide to use on them?

Creeping thistle is a perennial plant and grows mainly from an underground stem or rhizome and this makes total control difficult with one spray.

Yield losses of up to 15% have been recorded but they cause most damage by preventing animals grazing around them.
Frequent topping can reduce the root reserves but will seldom eradicate the problem as root fragments can lay viable and dormant for years.

This weed is best sprayed with Thistlex, Forefront, Lupo, MCPA or 2, 4-D in June before flowering and may need a second treatment later in the season to control any late shooting thistles.
In a reseed, both root fragments and seed can cause an explosion of creeping thistles.

(5) In some fields of permanent pasture, spear thistles are becoming a problem. What’s the best way to get rid of them?

Spear thistle only spreads by seed. Each plant lives for two years (like ragwort) producing a flatted rosette of leaves in year one and then the familiar ‘tree-like’ structure in year two.

Once controlled in the re-seed, it is rarely a problem in grazed fields except after poaching or other sward damage.

Topping is not effective to control the growth in year one but can be carried out on the second year growth before seed is set.
Chemical control options are the same as for creeping thistle.

(6) Clumps of Nettles in pasture have become a problem on my land. What’s the best way to control them?

Perennial nettle tends to grow in clumps in pasture and can prevent grazing.

The growth pattern of this weed makes it an ideal target for spot treatment with some of the Dicamba/Triclopyr/Fluroxypyr/Aminopyralid based products.

If the clumps are small and not too dense some of the Dicamba/CMPP based products will also contain them if sprayed on a regular basis.

High water volumes (400L/ha) are essential when spot treating. Treat before seed production for best effects.

By Anthony O’Connor, Teagasc Adviser, Galway/Clare Regional Unit and Tim Hyde, Environment Specialist, Teagasc, Athenry