There are a number of reports of increased presence of scutch grass in reseeded fields, in recent times. Scutch is the common name for Elytrigia repens, and is often referred to as couch grass, twitch or even switch grass. From the surface it looks very similar to perennial ryegrass, but is not nearly as productive or palatable to animals. The real differentiation between scutch grass and perennial ryegrass is below ground, as scutch grows using rhizomes. These are white stems growing underground, with little root nodules every few inches.
There are a number of reports of increased presence of scutch grass in reseeded fields, in recent times. Scutch is the common name for Elytrigia repens, and is often referred to as couch grass, twitch or even switch grass.
From the surface it looks very similar to perennial ryegrass, but is not nearly as productive or palatable to animals. The real differentiation between scutch grass and perennial ryegrass is below ground, as scutch grows using rhizomes. These are white stems growing underground, with little root nodules every few inches.
These rhizomes send up stems to the surface and these turn into leaf. Scutch spreads quickly underground and can cover large areas, shading out perennial ryegrass and other, more productive species.
Scutch is dormant during the winter and emerges again in springtime. This is another reason why it’s unproductive, as it doesn’t deliver feed in early spring, and it’s also the reason why it has been hard to control in 2024.
The main issues appear to be with early sown reseeds which were sprayed off in early to mid-April.
Due to the colder-than-normal temperatures at that time, it’s likely that the scutch wasn’t present in the sward when glyphosate was applied.
Another possible factor is that the fields were sprayed with glyphosate at too low a cover. In other words, there wasn’t enough time between grazing and spraying. While the perennial ryegrass may have bounced back sufficiently after being grazed, the slower-growing weed grasses like scutch, meadow fescue and timothy, or cocksfoot, may have been slower to bounce back after grazing.
If these grasses don’t make contact with the herbicide, then they won’t get killed off. What has happened in some instances this year is that as the field turned yellow, it then started to green up again as the scutch emerged. By right, these fields should have been sprayed again before cultivating or sowing.
There are no real treatment options for scutch once it’s established in a sward. Unlike in other crops, where scutch appears in grassland, it cannot be sprayed out of it without also killing the grass that you want to keep.
Effectively, there is one chance to control scutch and that’s when reseeding. The New Zealand advice for controlling scutch is to reseed in the autumn when the scutch is actively growing and thereby ensuring good translocation of the glyphosate to the roots and rhizomes of the weed grass.
Where there are severe infestations, the advice is to sow a short-term grass crop, such as Italian ryegrass or hybrid ryegrass, or even multi-species, and spray off with glyphosate again the following autumn, before sowing down to perennial ryegrass and clover at that stage.
Another option could be to create a stale seedbed by spraying the field off, allowing seven days before removing the grass then allow a few weeks to pass to allow the plants to fully die off. A light cultivation such as a stubble grubber could then be used to create a stale seedbed and allow weeds to emerge again. These weeds can then be sprayed off with glyphosate for a second time before going in and sowing.
There are two big drawbacks to these control methods, the longer time period required to get the new sward established and the subsequent loss of production. The other disadvantage is that there has been a swing away from autumn reseeding towards spring reseeding, as farmers require all of the land area in the autumn. By reseeding in autumn, that land is out of production at a costly time of year.
However, the options to control scutch are limited. Prevention is certainly better than cure and this relies on making sure that the weeds are actively growing when the glyphosate is applied. Secondly, make sure that the glyphosate is applied at the correct rate relative to the amount of glyphosate in the product.
Read the label carefully. For example, the label on Roundup XL states that “common couch [scutch] becomes susceptible at the onset of tillering and new rhizome growth, which usually occurs when plants have four to five leaves, each with 10-15cm of new growth”.
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