Now is the time to rattle ryegrass

15 February 2002

Now is the time to rattle ryegrass

RYEGRASS, the legacy of many a set-aside field in the north-east, needs nipping in the bud.

And this spring is the ideal time to do it, advises Mark Wood, agronomist with Wetherby-based Robert Crop protection, part of the Hutchinson Group.

The weed, both perennial and Italian, is increasing and until last year the run of poor seasons for spraying autumn herbicides is partly to blame, he believes.

"We tend to find a lot of grass mixtures being sown onto set-aside. Year-on-year bad weather and flooding have meant people have missed the ideal time for topping and the ryegrass has seeded."

Cereals sown after set-aside then face a tough grass weed challenge which even some otherwise good herbicides failed to meet last autumn.

"In general, they have done a good job giving up to 98% control. But 2% of a lot is still a lot."

Unlike wild oats, most ryegrass seed is relatively short-lived. So a concerted effort to clean up the rest and any more coming through this spring should be well worthwhile in the long term, says Mr Wood.

"We dont have any resistant ryegrass yet, but we live in fear of it. Blackgrass resistance is causing increasing problems in Yorks."

The yield benefit of ryegrass control is hard to pin down as much depends on weed density and crop population, says Syngentas Alison Kitchen. "But after such a string of bad autumns this season is ideal for a ryegrass clean up."

Controlling the weed, an ergot host, to avoid contamination of grain is becoming more important under crop assurance schemes, adds Mr Wood. "Merchants are looking for better quality samples."

For the most reliable results in cereals, assuming a good autumn residual programme has already been applied, he recommends Grasp (tralkoxydim) at full dose of 1.4 litres/ha at second to third node stage of the crop (GS32-33) and the advised 0.375% rate of adjuvant Output.

"You also need plenty of water – a minimum of 200 litres/ha. And spray quality is important, so avoid bubblejets."

For about £30/ha (£12/acre) the recipe should provide at least 90% control. "Its not cheap, and in winter wheat you have the option of Topik or Cheetah, but in my experience they only give 75-80% control at best.

The risk of encouraging dim resistance must also be borne in mind, he says. "Where I use Grasp it is specifically for ryegrass or wild oat control, and I always follow an autumn treatment using an anti-resistant strategy."

An autumn combination of new herbicide Graduate (flurtamone + diflufenican) and chlorotoluron seems to have been very successful against ryegrass, he says. &#42

Rampant ryegrass could be a set-aside penalty for the unwary.

&#8226 Growing problem from set-aside.

&#8226 Several years poor autumn control.

&#8226 Yield and quality penalties.

&#8226 Opportunity for spring clean.