Rush control normally takes place in June and July and involves the use of MCPA products.
owever, in recent years, Teagasc says drinking water monitoring results for Ireland have shown that a number of herbicides commonly used on grassland, such as MCPA, have been detected in drinking water.
It highlights that MCPA is water soluble and takes several weeks to break down. Rushes thrive in poorly-drained areas (with a water table near the surface), which are prone to run-off to nearby water bodies.
Teagasc has released the following tips on the use of herbicides when tackling rushes.
Herbicides can enter water bodies from:
- point sources (mainly in the farm or farmyard) – leaks from storage areas and spills or drips from handling operations such as mixing, filling and washing; or,
- diffuse sources (mainly in the field) – inputs arising during or after application from processes such as spray drift, run-off and drainage.
- What to do?
- Use non-chemical control methods, e.g., cutting, drainage, sward improvement.
- If spraying, target only the rush-affected areas and cut rushes one month before, or one month after spraying to improve the effect of the spray.
- Consider weed wiping with an appropriate herbicide (not MCPA) as a rush control option.
- It is essential to take great care and follow best practice procedures when using any pesticide and particularly so in the case of herbicides used on grassland.
Weeds in grassland
- Don’t underestimate basic grassland husbandry such as lime, fertiliser, topping or reseeding as weed control measures.
- Low levels of weeds do not affect grass production and are beneficial to the environment.
- A vigorously-growing grass sward can outcompete weeds and prevent new weeds growing.
- Spraying at the right time doubles the effect of the spray.
Dos when using herbicides:
- do read the product label instructions carefully and plan the treatment in advance;
- do inform yourself of the location of all nearby water bodies (ditches, streams, ponds, rivers, lakes and springs);
- do find out if any groundwater body or surface water body in your locality is used as a drinking water source and, if so, the location of the nearest abstraction point;
- do ensure that pesticide products are stored in a secure, dry area which cannot result in accidental leaks or spills – empty, triple-rinsed containers should be disposed of in accordance with the ‘Good Practice Guide for Empty Pesticide Containers’;
- do ensure that application equipment is properly calibrated and in good working order;
- do take every precaution during mixing and preparation to avoid spills and drips – minimise water volumes (rain and washings) on the handling area;
- do consider using drift-reducing nozzles if spraying – keep the spray boom as low as possible to the ground and use the coarsest appropriate spray quality; and,
- do clean and wash down the sprayer at the end of the day, preferably in the field and well away from water bodies or open drains. Tank washings should be sprayed onto the previously sprayed area, on a section far away from any water body, observing the maximum dose for that area.
Don’ts when using herbicides:
- don’t perform handling operations (filling, mixing or washing the sprayer) near water bodies, open drains or well heads – maintain a distance of at least 10m, and preferably 50m where possible;
- don’t fill the sprayer directly from a water body;
- don’t spray if the grass is wet or if heavy rain is forecast within 48 hours after application;
- don’t spray during windy conditions;
- don’t spray near open drains, wells or springs;
- don’t spray on waterlogged or poorly-draining soils that slope steeply towards a water body, drain, well or on any other vulnerable area that leads directly to water; and,
- don’t discard sprayer washings down a drain or onto an area from which they can readily enter a water body.
Statutory ‘no-use’ zones (called safeguard zones) apply around drinking water abstraction points, ranging from 5m to 200m depending on the size of the supply. Your local authority or the National
Federation of Group Water Schemes can advise on this.
Careless storage, handling or use of pesticides can easily cause breaches of the legal limit for pesticides in drinking water. A single drop of pesticide lost to a water body such as a typical stream (1m wide, 0.30m deep), for example, can be enough to breach the legal limit for pesticides in drinking water of 0.1 part per billion along 30km of its length.
Check how near water bodies (ditches, streams, ponds, rivers, lakes, etc.), drains or wells are to where you are working. Find out if the treatment area is in the vicinity of a drinking water abstraction point or well.