Grass growth rates have improved over the last week, but remain significantly below normal for the time of year.
Swards, in many cases, have been grazed bare and once growth kicks in, there is likely to be potential in the sward to compensate for the lower levels of growth up to now.
The same can be said of weeds and with grass starting at a disadvantage in swards that have been possibly grazed tighter than desired or which may remain under pressure. There is therefore a greater risk of weeds gaining a stronger foothold in the sward. This statement is true of rushes, docks, thistles and nettles.
The optimum timing for treatment of weeds, such as thistles, docks and nettles, is what is known as the rosette stage. For docks and nettles, this is when plants are at a height of about 150mm to 250mm or 6” to 10”.
The growth pattern of thistles is slightly different, in that leaves grow outwards quicker. This allows greater potential to optimise spray coverage at a lower height, with the best time to control thistles recommended at approximately 200mm (about 8”) in height.
In addition to maximising spray coverage, weeds at this height will typically be growing at their most active. This will encourage chemicals to be taken in and transferred around the plant quicker. If weeds have not reached this stage, then the advice is to delay treatment.
Spot spraying is also likely to be a more realistic option where weeds are present in isolated cases
This may not be possible in silage swards that have been closed early. If this is the case, a decision will need to be taken on temporary treatment or possible spot-spray treatment.
Spot spraying is also likely to be a more realistic option where weeds are present in isolated cases and the aim is to keep on top of them and stem their spread.
Time of application
It goes without saying that spraying should not take place on a windy day or where there is a risk of spray drifting. The optimum conditions are on a dull day.
Where this is not possible, then spraying early in the morning or late in the evening should be the target during periods of high daytime temperatures or sunny weather.
Where spraying is carried while sunshine is strong, then water droplets falling on the leaves will act as a magnifying glass.
The sun’s rays can burn and damage the surface of the plant, which in turn can reduce the ability of the plant to absorb chemicals.
There are numerous herbicides on the market that are formulated to target one particular weed or a combination of weeds. It is important to consider your choice and select the weed that best addresses the greatest challenge.
There can be a temptation when spraying grassland swards to mix sprays with the aim of covering a greater number of weeds than would otherwise have been possible with the one application.
Examples of this include mixing sprays that have a hormonal mode of action (such as MCPA, CMPP or 2.4-D) with sprays which have a systemic mode of action (such as Dockstar, Pastor, etc).
This is advised against, as sprays with a hormone mode of action works quicker on the plant and begins to shut it down immediately.
As the plant begins to shut down, movement of the systemic herbicide that is fully translocated down to the roots will be limited and the herbicide will not get a chance to work into the root system.
This will hamper the success of the treatment and risk your investment being lost.
Sprayer or weed licker?
A weed licker will generally not achieve as successful a kill as spraying.
The area of the plant which comes in contact with the herbicide will influence the success of the kill and this is usually best achieved by spraying.
Weed lickers are usually mainly used when weeds are at a set height above grass land.
Weeds at this height are usually mature weeds or gone beyond the optimum stage recommended for treatment.
Treatment at this stage will bring about a limited kill and will generally not prevent weeds from re-emerging.