Teagasc is reporting that many spring wheat crops planted out over recent weeks are now emerging and looking well and herbicide management is very important.
One of the first jobs that growers will have to tackle is that of effectively controlling weeds within these crops.
Herbicide resistant wild oats are problematic in this regard but so are a number of difficult to control broadleaf weeds.
Herbicide management
For years, Irish growers had the standard of a CMPP herbicide partnered with a sulfonylurea to avail of. This approach, basically, took care of everything from a weed-control perspective.
But it’s not so simple anymore. Teagasc tillage specialists are confirming that weeds which were not a problem in the past, are now becoming much harder to control.
These include corn marigold and chickweed.
Corn Marigold
Corn marigold can be distinguished by its bright yellow flower that appears in late June and early July. It’s often considered a legacy from old sugar beet ground and thrives in sandy soils with a low pH value.
According to Teagasc sulfonylurea chemistry is not working on corn marigold in the way that it used to. So growers will have to work on the basis that such an approach will not work when it comes to controlling this particular weed.
What’s more, a range of other chemistries won’t work individually on corn marigold.
Teagasc is now recommending products containing clopyralid to control corn marigold. This approach comes with the added proviso that the herbicide chosen must be applied at full rate.
Chickweed
Meanwhile, Teagasc ‘chickweed resistance trials’ are ongoing. This is a weed that can be a major problem at harvest time. But like corn marigold, it is showing the same level of resistance to sulfonylurea chemistries.
As a result, Teagasc is now recommending the use of herbicides containing fluroxypyr, as their active ingredient to control chickweed infestations.
Again, full label rates must be applied, in order to get adequate control.
Herbicide resistance
If growers know that they have a problem with herbicide-tolerant weeds, the advice from Teagasc is very clear – do not use the chemicals that were used up to this point. Such an approach will not solve the problem.
Rather, it’s a case of using new chemical mixes to control resistant weeds.
Where crops of spring barley are concerned, annual meadow grass can become an issue at harvest, in cases where establishment was poor and the cereal did not get off to the best start.
One way to minimise the problem is to adopt a stale seed bed approach and apply glyphosate prior to ploughing. Getting the crop off to the best possible start is also a priority.
If chemical control is required for annual meadow grass, the option recommended by Teagasc is to apply pendimethalin prior to emergence.
However, this approach requires sufficient moisture within the soil at time of application. This could be an issue with some late-sown spring barley crops.