Using herbicides safely as part of a sustainable rush control program
Good weed control in grassland is just as important as it is in an arable field, whether it is a young sward trying to compete with broadleaved weeds or, in an older established sward where docks or rushes have crept in. Weeds reduce productivity, forage quality and in some cases can harm livestock. As all business strive towards a more efficient future, effective weed control has never been more important.
Why are rushes such an issue?
Rush seeds will survive in the soil for at least 80 years, meaning that no matter which option you use, there will be a requirement for follow up treatments and a change of practice.
A healthy grass sward will always out compete juvenile rushes, so in order to eliminate rushes from a field, action needs to be taken to improve the outlook for the grass in the field.
Basically, a change of mind set is required, you’re not trying to kill the rushes, you’re trying to grow more grass. To do that, firstly you have to treat the rushes, commonly by spraying, weed wiping, cutting or flailing, thereafter, you need to rectify the real reason the rushes are there. Is it a drainage issue, a pH issue, or a nutrient issue such as Phosphate or Potash? You need to ascertain what is holding back your grass, once you know this, controlling rushes should be a much easier task.
What are the herbicide options and what do you need to consider?
Where rushes are present and becoming increasing prevalent, it suggests there are wider issues at play with rushes favouring poorly drained, hungry soils, where grass growth is sub-optimal. Herbicides can be used to control them, but only as part of a broader approach to tackling the problem.
There are two main types of herbicides used for rush control, MCPA and glyphosate.
- MCPA (2-methyl-4-chlorophenoxyacetic acid)
MCPA is a common and effective grassland herbicide which has been used for many years. It is a selective herbicide, with a wide spectrum of weeds controlled and while generally safe to grass swards it can check growth and damage clover and may not be suitable for more species rich swards. It is also water soluble and can take several weeks to breakdown so care needs to be taken when using near the water environment, as MCPA in a water ecosystem has the potential to be catastrophic. This also means that in the poorly drained, or waterlogged soils, where rushes are most likely to be found, there is also a high risk of MCPA finding its way into watercourses through diffuse pollution in the form of run off.
| Some of the key considerations when using MCPA on grassland | |
|---|---|
 | Read the label carefully and follow recommended rates. MCPA products are extremely harmful to the water environment and must not be applied within 5 metres of the top of the bank of a watercourse or dry ditch. Application to waterlogged sites or to areas with standing water must be avoided as MCPA can persist in anaerobic conditions, leading to diffuse pollution. Care should also be taken to ensure no heavy rain is forecast in the following 48 hours. |
| • Operators must have valid PA1 & PA2 with the sprayer NSTS tested within the last 3 years (unless the sprayer is under 5 years old) | Drift can also lead to diffuse pollution and spraying must take place in appropriate weather conditions. Equipment must be fit for purpose and operators must have the relevant qualifications. Spraying should never be undertaken in winds over 6 mph. Tip: When used at their rated forward speed and pressure, low drift nozzles can lead to significant reductions in drift. |
| • Sprayer must be in good working condition with faults recorded and repaired. | |
| • Wind speed under 6 m.p.h. | |
| • Boom height 50cm when using tractor sprayer and driven at a steady speed (10-12km/hr) | |
 | MCPA must only be applied using a horizontal boom sprayer. It must not be applied by weed wiper, knapsack sprayer or other handheld equipment. |
 | MCPA should be applied to actively growing rushes before flowering, typically from the end of May to early July. Earlier spraying to smaller plants is more effective than applications to mature plants. Water volumes should be a minimum of 200 l/ha (check label) and the addition of a wetter can help the spray bind to the surface of the rushes better. |
 | Never fill sprayers directly out of watercourses or mains supplies. Care should always be taken to prevent leaks and spillages at the filling and storage area with emptying and washing undertaken in the field where possible (away from watercourses) and where run-off cannot enter water courses. Any residues remaining in the sprayer can cause significant damage to other crops subsequently sprayed with the same equipment. Empty containers should also be triple washed before appropriate disposal and should never be re-used for another purpose. |
 | Livestock should be kept out of treated areas for at least 2 weeks and until the foliage of any poisonous weeds such as ragwort has died sufficiently to become unpalatable. Spraying first thing in the morning, or spraying in the evening can reduce the risk of scorching or stressing the grass. Spraying should never be undertaken when temperatures exceed 25°C. Grass for hay or silage should be sprayed at least 4 weeks before cutting. |
- Glyphosate
Glyphosate is a very common systemic herbicide. Unlike MCPA it is not selective making its use on grass swards unsuitable unless the field is being reseeded. One key difference however is its suitability for use in handheld equipment for spot spraying or in a weed wiper, allowing targeted treatment. This has several benefits:
- Wetter areas can be reached, by using a quad bike to tow the weed wiper.
- Targeted applications reduce the risk to non-target vegetation and the water environment with no drift when weed wipers are used.
- Targeted applications also mean lower volumes of herbicide and water are required, further reducing the risk to the water environment.
| Some of the key considerations when using Glyphosate on grassland | |
|---|---|
 | Always read the label - with glyphosates varying in levels of active ingredient, the label will contain the recommended application rate for the chosen target. In addition, the label will also provide advice on maximum application levels. |
 | A period of heavy grazing (avoiding poaching) before application can help ensure there is sufficient height differential between the targeted rushes and the grass sward. This helps avoid damage to non-target species. |
| • Knapsack operators must have valid PA1 and PA6 | Operators should be suitably qualified, and equipment well maintained. Care should be taken in species rich swards to avoid non-target species. Safety of both the operator and wider environment should also be considered. |
| • Knapsacks must be inspected regularly by a competent person with faults recorded and repaired | |
| • Weed wiper operators must have valid PA1 and PA2F qualifications | Operators should be experienced and suitably qualified both with the weed wiper and quad bike. Equipment should be well maintained and driven according to recommended use to ensure the safety of both the operator and wider environment. |
| • Weed wipers should have been NSTS tested within the last 6 years if more than 5 years old. In addition they should be regularly checked and repaired with faults recorded. | |
| | MCPA should be applied to actively growing rushes before flowering, typically from the end of May to early July. Earlier spraying to smaller plants is more effective than applications to mature plants. Water volumes should be a minimum of 200 l/ha (check label) and the addition of a wetter can help the spray bind to the surface of the rushes better. |
| | Never fill sprayers directly out of watercourses or mains supplies. Care should always be taken to prevent leaks and spillages at the filling and storage area with emptying and washing undertaken in the field where possible (away from watercourses) and where run-off cannot enter water courses. Any residues remaining in the sprayer can cause significant damage to other crops subsequently sprayed with the same equipment. Empty containers should also be triple washed before appropriate disposal and should never be re-used for another purpose. |
| | Always check the label for grazing and cutting intervals. These should be clearly marked. Many well-known glyphosates have a grazing interval of 5 days however this can vary particularly where generics are used. If in doubt, speak to a BASIS qualified agronomist. |
How can non-chemical options be used effectively?
While chemical control options are generally the quickest, and most economical option to control rushes, sprays are by no means the only ways of controlling rush infestations. A planned cutting regime will have a detrimental impact on rush populations, If rushes are cut twice a year, you will achieve a noticeable reduction in the population and the strength of the plants. Cutting will also stimulate grass growth and improve grazing quality, putting further pressure on rushes.
Another method in the control of rushes is the targeted use of on farm nutrients such as FYM and slurry. They are a valuable source of nutrients which will help to put pressure on rush populations. Liming to improve soil pH will undoubtedly have a positive impact in the fight against rushes.
Deep ploughing can be effective in a rush control programme. However, remember this is a high cost operation and one that must be done in conjunction with a full reseed and provide ideal growth conditions for the new grass. Establishing a strong grass sward will keep rushes at bay. Reseeding in non-ideal conditions however could promote rush growth. If going to the length of a full reseed, you should seek professional advice from a BASIS registered agronomist to develop a functional programme.
Remember that in rush control, the cheapest option might be the most expensive in the long term, don’t cut corners, seek advice and invest what is required to eliminate rushes and establish a high output sward of grass.
Can I manage my grassland differently to help control rushes?
Rotational grazing has become fashionable and is a very effective way of growing grass, with that in mind, it is clear that establishing a rotational grazing system will have an impact on rushes. The advantages here are two fold, firstly by giving grass an intensive grazing followed by a rest period, grass growth will increase and the sward will be more competitive. Additionally, rotational systems prevent over grazing which is a major issue in the establishment of rushes. A cutting programme alongside the rotation will also help to put pressure on rushes and ensure they are more palatable, encouraging cattle to graze the rushes out.
Prevention is always better than cure!
As we look to a future of low input, high output agriculture it is clear that our farming methods will have to change. We have all seen fields where rush populations are completely out of control and will take a huge investment of labour and money to control, these fields didn’t get into that state overnight. The earlier you intervene, the less money you’ll have to spend and the lower the impact you’ll have on the environment. Throughout the year, swards should be monitored and if they aren’t performing the way they should be, a prompt diagnosis and treatment will result in the best and cheapest outcome.
You don’t need to kill them all
Remember that rushes have an important role to play in creating habitat for native fauna, producers should keep in mind the impact of their actions on the wider environment, including biodiversity. Before you start developing a rush control plan, take a look at the habitat and species present and make a plan based on what you find.
Find our more on our 'Providing for wading birds' webpage.
If you'd like more detail on Controlling Rushes, download our Technical Note (TN701): Control of Rushes which is also available in Gaelic.
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