Prevention is the first step in reducing weeds and pesticide use on the farm
Before reaching for the chemical sprays farmers need to remind themselves of the principles of Integrated Pest Management (IPM). File Picture.
One of the main goals of the Farm to Fork Strategy and the EU Green Deal is to reduce the use of pesticides on farm by up to 50%.
Before reaching for the chemical sprays we need to remind ourselves of the principles of Integrated Pest Management (IPM) one of which is to look at other biological, physical or other non-chemical methods to prevent and reduce grassland weeds.
IPM is a process of decisions and actions and prevention is the first step to reduce weed infestation in grass swards. Practices such as poaching and harvesting heavy crops of silage encourage weeds into swards.
With a very heavy crop of silage there is little light getting down into the sward, which in turn reduces grass tillering leading to open swards and thus allows weed infestation.
It may not be possible on all farms, but rotate fields between grazing and silage annually. Suppression of weeds is the second step.
This means ensuring that perennial ryegrass remains competitive over weeds. Grazing regularly and tightly will encourage grass tillering and suppress weeds particularly annual ones such as chickweed and redshank.
Optimum soil fertility especially soil pH and phosphorous will ensure perennial ryegrass persists instead of weeds. Where ground has been damaged by poaching spread 6kg/acre of grass seed to encourage grass plants back into these open areas.
Rather than spraying a field infested with docks for example a number of times in its lifetime, ask yourself; should the field be reseeded instead?
You should reseed 8-10% of your farm annually because established correctly reseeded fields have higher grass production, respond more efficiently to nutrients applied, and have reduced weed population compared to old swards.
Look at the threshold of weeds in a field and depending on amounts/type of weed/growth stages consider other non-chemical ways of controlling weeds such as tight grazing, topping or baling.
If using a spray make sure you use the correct product to cover the range of weeds in the sward and also at the correct rate.
Are you using the right product at the right time of year or at the right growth stage?
There’s no point in spraying if you are doing it wrong as you are wasting your money but also the product can be harmful to the environment if it’s not being taken up by the targeted weed.
Carefully follow instructions from product labels of buffer zones which can range from 1m up to 30m from watercourses. You can reduce these buffer zones if you replace your sprayer nozzles with special drift reducing nozzles – check with your local approved pesticide equipment inspector about these.
If you are a registered pesticide user remember you must get your sprayer tested every three years.
You can get more details on how to become a registered user or where to get your sprayer tested online www.pcs.agriculture.gov.ie
Along with optimum soil fertility, the timing of reseeding is one of the most important factors affecting weed establishment. Always aim to reseed in the spring or summer.
As temperatures reduce into the autumn, weeds tend to have a better chance to establish than grass as the window for post-emergence spraying and fertiliser applications reduces.
Always use a post-emergence spray after reseeding when the weeds are strong enough generally four to six weeks after reseeding (check product label always) and graze the new sward at light covers to encourage grass tillering and prevent weeds establishing.
- Gráinne Hurley PhD, Teagasc/Dairygold Joint Program.
