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Control of Tough Herbaceous and Woody Weeds with Roundup Pro Biactive


This general category includes weeds such as Rosebay Willow Herb, Docks, Thistles, Mugwort, Coltsfoot, Brambles, Ivy, Buddleja, Gorse and self-set tree saplings. They are all perennials with a reputation for invasion of non-cropped areas and being difficult to kill. They are commonly found in situations such as overgrown waste ground and roadsides, neglected industrial or urban sites and forgotten yards and disused areas. Roundup Pro Biactive can be used as a foliar treatment in the spring and summer at or just after flowering and as a cut stump treatment in the dormant season.

Remember always to take a planned and programmed approach to weed control in such areas – one well timed application may kill off all those weeds present but if no follow-up activity is carried out weeds will simply re-infest the area and within a few years it will have reverted to its original state.

Control with Roundup Pro Biactive

Foliar treatment

Roundup Pro Biactive is an ideal treatment for dealing with tough weeds on roadsides and waste ground. Timing will depend upon species mix but most will be controlled by an application in June or July, from when the weeds come up to flowering but before they die-back.

The combination of Roundup Pro Biactive plus Mixture B NF, at 2% of total spray volume, will help improve the reliability of control especially on woody and waxy-leaved weeds.

Cut Stump

Treatments are best made from November through to March or April, and not during the period of active sap flow

Application of Roundup Pro Biactive must be made to a fresh cut so that uptake into the phloem is maximised. A two-man operation is often the most practical for a quick post-felling treatment.  If more than a few minutes of time have elapsed, recutting the stump will restore the effectiveness of the application. (Uptake is almost immediate from a fresh cut and will be rainfast within 10 minutes. Application to a cut that has partially sealed means absorbtion is slow and rain within 6 hours will wash some of the product off).  Apply in a solution with clean water using a knapsack sprayer, spot gun or paintbrush.

Chemical Thinning

This method works from slightly earlier in the season, late summer, which may be useful to use before stump painting could commence in November.  It has the benefit of not requiring the stump to be freshly cut, so it can be used where they have already been cut back, or where the plant is to remain in situ.  It is also easy to see which areas have been treated.

Neat Roundup Pro Biactive is introduced straight into the phloem through a hatchet cut into the bark of the standing plant or stump. The cut can be made using a small axe - it is advisable to make a second cut under the first to catch any surplus herbicide.  Alternatively a small hole can be drilled at an angle downwards towards the centre of the trunk. A spot gun with a solid stream nozzle is recommended.  A cut is required for each 10cm diameter of trunk, work out how many are needed and space them round the girth. e.g. a trunk of 30cm diameter requires 3 cuts.

Rates, Timings and Water Volumes

MethodDose Rate of Roundup Pro BiactiveDose Rate of Roundup ProBiactive450Application Advice
Tough Weeds - Foliar Spray

5l/ha or in waste ground & amenity situations 5l/ha + Mixture B NF at 2% spray volume.

4l/ha or in waste ground & amenity situations 4l/ha + Mixture B NF at 2% spray volume.

Spray as weed is flowering, but before die-back. Typically June/July, depending on species. Spray any re-growth with same rates before end October.

Woody Weeds - Cut Stump
  • 10% solution (deciduous species)
  • 20% solution (Evergreens and coniferous species)
  • 8% solution (deciduous species)
  • 16% solution (Evergreens and coniferous species)

Apply to freshly cut stumps with a knapsack sprayer, spot gun or paintbrush during the dormant season (November to end February)

Woody Weeds - Chemical Thinning 2ml per 10cm diameter of trunk 1.6ml per 10cm diameter of trunk

Two hatchet cuts per 10cm trunk diameter, one below the other to catch drips.
Drill one hole with 8mm drill approx. 40mm long downwards radially towards centre, per 10cm trunk diameter

Spot Treatment in Knapsack Sprayer

Most knapsack sprayers are supplied with a set of 4 deflector nozzles giving different swath widths but all delivering 200l/ha of water at 1 bar pressure and a walking speed of 1 metre per second.

Area SprayedRate of Roundup Pro BiactiveRate of Roundup ProBiactive450Volume of Water
50 Square Metres 25ml 20ml 1 litre
500 Square Metres 250ml 200ml 10 litres
1,000 Square Metres 500ml 400ml 20 litres