Grassland Agronomy Update – July 2016


Welcome to the Grassland Agronomy Update from Dow AgroSciences.

These regular technical notes are a seasonal commentary to help those interested in improving grassland productivity on dairy, beef, sheep & equestrian enterprises.

You can claim 2 CPD points for subscribing to this email update.


  • Spraying clover in grass swards
  • Tackling Heracleum
  • Who can buy sprays?
  • Dock beetle and Ramularia rubella – help or hindrance?
  • Application advice on the Grassland Weed App
  • How flowering affects spray efficacy
  • FAQs
  • Dow AgroSciences’ show dates

Spraying clover in grass swards

If weeds need controlling and clover is present then what are the options?

docks & clover

Docks and Clover

Where weed infestations are small or concentrated in particular areas, applying herbicides as a spot treatment or through a weed wiper will kill the weeds, leaving the clover relatively unscathed.

At best a weed wiper will deliver 70% of the control that an overall spray application would achieve. Currently just glyphosate has an approval for this method so it does have limitations.

Where weeds account for 20% or more of the field, there may not be enough saving in bagged nitrogen fertiliser to be worth saving the clover.
In these situations, use an effective translocated herbicide such as Doxstar®Pro, Pastor®Pro or Thistlex®, and re-introduce the clover later by over-sowing 6 weeks later. If using Forefront® T, wait for 4 months.

Oversowing – have a plan

The key is allowing the clover seed to fall on bare, moist soil so it can germinate. This can be done with a combination of tight grazing and grass harrowing or direct drilling.

On cutting ground

  • Check and correct pH, P and K in the previous autumn
  • Spray with an appropriate translocated herbicide at least three to four weeks before cutting
  • After cutting, stock with dry cows or youngstock. Do not apply N
  • Grass harrow – two to six passes to create 25% bare ground
  • Broadcast clover seed and grass harrow
  • Roll and/or stock with dry cows or youngstock for six to ten days
  • Remove stock and rest for three to four weeks, then mob stock graze and repeat until winter

On grazing ground

  • Check and correct pH, P and K in the previous autumn
  • Spray with an appropriate translocated herbicide in the autumn
  • Grass harrow dense swards previous spring and autumn
  • Graze tight March/April (for April sowing), although sowing is preferable in July
  • Grass harrow – two to six passes to create 25% bare ground
  • Broadcast clover seed and grass harrow
  • Roll and/or stock with dry cows/youngstock for six to ten days
  • Remove stock and rest for three to four weeks, then mob stock graze and repeat until clover has established

Tackling Heracleum

The number of Hotline queries on hogweeds has increased this year. But what can be done to control Apiaceae weeds?

Giant Hogweed

Giant Hogweed

Hogweeds (Heracleum) are a genus of about 60 species of biennial and perennial herbs in the carrot family Apiaceae. Many species exhibit lofty, upward-facing white flowers borne on the top of thick, bristly stems. They are close relatives of cow parsley.

Giant hogweed (Heracleum mantegazzianum) is a native of the Caucasus Mountains, growing four to five metres tall. It is now a serious invasive weed across Europe including the UK, after being introduced as a garden plant in the early nineteenth century.

Giant hogweed can cause severe photo-dermatitis if its sap gets onto human skin, causing burns when exposed to sunlight.

Common hogweed (Heracleum sphondylium) is also common in Europe and its sap can also cause rashes and skin irritation.

Classified as an invasive alien, it is an offence to cause giant hogweed to grow in the wild anywhere in the UK. It can also be subject to Anti-Social Behaviour Orders, where occupiers of giant hogweed infested ground can be required to remove the weed or face penalties.

Controlling hogweed

Giant Hogweed 5When they are small, and before they have produced a flowering spike, hogweeds can be pulled up by hand. It essential to cover arms and legs and to wear a facemask when doing this.

Cut plant debris, contaminated clothing and tools are potentially hazardous too. Wash any skin that comes into contact with the plant immediately.
If the infestation is too large, or it is too late to pull the plants up, chemical control should be considered.

Young foliage should be sprayed in May and the plants re-treated in August and September if needed. Or summer foliage can be cut back down and the regrowth sprayed. Mature plants are likely to need more than one treatment to kill them.

Dying giant hogweed is a controlled waste and if taken off-site can only be disposed of in a licensed landfill site with full documentation.
The smaller native hogweed is not classed as a controlled waste, but should still be disposed of with care to avoid human contact.

Dow herbicides?
Currently our most effective solutions are those that contain aminopyralid and can be applied via a knapsack: Synero®, Garlon® Ultra or Icade®.

Who can buy sprays?

All farmers who are spraying herbicides now need to be certified – but they don’t need certification to buy them.

Grassland StoreNew legislation, under the Plant Protection Products (Sustainable Use) Regulations that came into force at the end of 2015, now requires all sprayer operators, however old they are, who are applying professional pesticide products (PPPs), to have a Specified Certificate.

Farmers who were born before 31 December 1964 and previously sprayed under the ‘Grandfather Rights’ exemption, must take the Level 2 Award in the safe use of pesticides replacing grandfather rights, or take the existing Level 2 safe use of pesticides (PA) certificate.

If they do not want to take the tests, they must hand over the spraying to a family member or employee who has the correct qualifications, or use a spray contractor.

Buying PPPs

However, uncertified farmers can still buy most pesticides, such as DoxstarPro and Thistlex over the counter, as long as they know that the person who will be using them is certified. There is no legal obligation to show any certificates to the person selling the products.

The farmer buying the products needs to ensure the intended sprayer operator is suitably qualified, or will be working under the direct supervision of someone who is suitably qualified, perhaps because they are undergoing training.

This legislation applies to all livestock farmers and smallholders, many of whom may only occasionally use professional pesticides. Even those using products such as Grazon®Pro in a knapsack on their own farm, have to be certified.

Specified certificates, previously known as certificates of competence, are issued by City and Guilds Land Based Services. Visit the National Proficiency Tests Council at or the local agricultural college for PA2 (ground crop sprayer – mounted or trailed) and PA6 (hand-held applicator) courses.

Existing PA certificates of competence in the safe use of pesticides continue to be recognised under the new legislation.

For more information see the Changes to Legislation: A Guide for Grassland Herbicides on the Dow AgroSciences website

Dock beetles and Ramularia rubella – help or hindrance?

Dock beetles (Gastrophysa viridula) and the fungus Ramularia rubella can attack dock plants – but are they helpful when spraying?

dock beetle cropped

Dock beetle

Green dock leaf beetle is a native beetle, which is green with a metallic shimmer. Depending on the light they can look gold green, blue, purple, violet or red. Their strong legs also shimmer.

They feed mainly on any of the Rumex species, including broad-leaved dock. Their larvae can only completely develop on Rumex.

The females breed from March to October, laying more than 1,000 eggs in clusters on the underside of the dock’s leaves. The segmented larva hatches after three to six days. After three moults, the larva pupates in a burrow 2cm underground, and the new adult emerges six to nine days later.

Ramularia rubella fungal spores attach onto docks in moist conditions. Their tentacle-like hyphae enter the plant through the stomata on the underside of the leaves. Once inside the plant, they push between the plant cells and feed off the nutrients in the leaf.

Ramularian and dock beetle damage

Ramularian and dock beetle damage

Ramularia can also produce toxins, which are activated by sunlight and cause plant cell death. Dead cells create large dark spots with creamy centres on the leaves.

The fungal spores are airborne and released – spreading to other leaves on the same plant and to other docks nearby.

How does this affect spray treatments?

For best control, docks should have young, fresh, actively growing leaves when they are sprayed.

Dock leaves that have been shredded by dock beetle or are covered in purple splodges hinder uptake and translocation of herbicides.

Ramularia is more of a problem in spring, but dock beetles are more of a problem from June through to August.

If affected docks are to be treated, it is best to top the large plants and wait for two to three weeks of fresh regrowth, before spraying with a translocated herbicide such as DoxstarPro.

Application advice on the Grassland Weed App

Grassland App Weed IDThe Dow Grassland APP is available on iOS, Android and Windows platforms. It has a lot of useful support features for those involved in grassland weed control.

An intuitive easy to use APP which:

  • Enables a deep drill of all our grassland technical knowledge
  • Choose a combination of up to 3 weeds and find the best solutions for their control
  • Pick a weed size and get guidance on whether to spray or not
  • A tank dose calculator tool
  • Create a spray record
  • Manages Forefront T stewardship requirements

If you haven’t already downloaded the Dow Grassland APP you can do so with these links:
App Store / Google Play / Windows Store 

If you have already downloaded the APP, please ensure you are using the latest version.


How flowering affects spray efficacy

Spraying herbicide at different times in a plant’s life will significantly affect the result.

2. It is too late to treat buttercups when they are flowering and the field is yellow

All plants have a vegetative stage and a reproductive, or flowering stage.

All the time the plant is not producing seed heads, active growth focuses on the production of new roots and leaves.

During sexual reproduction, seed head development is triggered by mechanisms based on temperature and day length. The stems of the inflorescence buds elongate upwards to carry the developing flower above the ground.

The key aim of translocated herbicides is to travel deep down into the roots to exact a high level of control. This is best done when the plant is growing in a vegetative state.

At flowering, most of the nutrients and water are being carried up towards the flower, rather than down into the roots.

The effect of spraying perennial weeds at flowering is likely to be reduced control. Although the top growth may look like it has been killed, it’s the root control that that determines success and they may not have received sufficient herbicide to make that certain.

Dow AgroSciences advises farmers to spray perennial weeds such as docks, thistles, nettles, buttercups and ragwort BEFORE they flower for best results.

If that proves difficult, then accept that control may be 50% to 80% of what you would expect to achieve or top and spray resulting regrowth some 2 weeks later.


Q: How can I control yellow rattle in grassland?
Forefront T will give the best control, as long as the field is to be grazed with cattle or sheep, or is treated after the last cut of the year. Where fields are being cut for hay or silage use GrazonPro instead.

Q: How soon can I slot-seed grass or clover into a field after treating with Forefront T?
Grass seed can be stitched in after four weeks but for clover you will need to wait 4 months after spraying with Forefront T.

Q: Is it safe to cut for hay 14 days after spraying with Dow AgroSciences grassland products?
Yes, it is safe to cut hay. However, for best long-term weed control, Dow AgroSciences advises leaving up to 28 days before cutting the crop, to allow the active ingredients to reach right down into the roots for more effective control.

Q: As a farmer, do I need to have the Dow Grassland App to be able to receive Forefront T stewardship recommendations from my agronomist?
No, a farmer just needs to be able to receive and respond to the stewardship recommendation email. This can be done via a PC, tablet or smartphone.

Q: Will DoxstarPro have any effect on nettles?
Yes, DoxstarPro will give moderate control and a reduction in top growth, as will Thistlex. However, PastorPro or GrazonPro are better alternatives for using against nettles.

Grassland Show 2105Show Dates

The technical team from Dow AgroSciences will be out and about at many shows and events this summer, talking to farmers and agronomists and answering questions on how to tackle weed problems in their fields.

Catch the team at:

July 6th/7th Livestock Event Brimingham NEC
Nov 16th AgriScot Edinburgh



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DoxstarPro contains fluroxypyr and triclopyr
Forefront T contains aminopyralid and triclopyr
Garlon Ultra contains aminopyralid and triclopyr
GrazonPro contains clopyralid and triclopyr
Icade contains aminopyralid and triclopyr
PastorPro contains clopyralid, fluroxypyr and triclopyr
Synero contains aminopyralid and fluroxypyr
Thistlex contains clopyralid and triclopyr

Dow AgroSciences Limited, Latchmore Court, Brand Street, Hitchin, Hertfordshire, SG5 1NH.Tel: +44 (0) 1462 457272. Technical Hotline: 0800 689 8899 email: |