Independent agronomist Peter Riley looks beyond this year’s arable crops and plans a longer term assault on difficult and obvious weeds such as black-grass and poppies. He also saw a lot of sow-thistles and thistles on his travels last season, but not in East Anglia where he applied his longer term policy based on using propyzamide-based herbicides in oilseed rape.
“I am committed to recommend propyzamide in most of our rape as a rotational use policy for grass-weed control. And if I can also get control of difficult broad-leaved weeds such as poppies and mayweeds, then AstroKerb, which contains propyzamide and aminopyralid, is what I will use. I had seen this herbicide in trials for a number of years before it came onto the market and, being mindful of poppies on certain soils in East Anglia, it has formed a key part of our weed control policy. It has also given good control of mayweeds, sow-thistles and thistles, all of which appear to be building up. I find the use of post-emergence spring-applied herbicides to control these broad-leaved weeds difficult to time, so I am happy that an autumn application of AstroKerb will remove them effectively and earlier.”
He explains that he has moved his oilseed rape herbicide strategy away from expensive pre-emergence coformulations to one of straight metazachlor + clomazone pre-em followed by AstroKerb. “This costs a similar amount but results in excellent weed control.”
Peter advises that AstroKerb is used at the same time and under the same criteria as Kerb 500.
“I was worried last year about the big canopies in rape, but it appeared to be no issue. I am hoping this will be the same this season, as I am seeing many tall rape crops with vigorous canopies.”
David Roberts of Dow AgroSciences refers to trials done with Kerb where it was applied to a crop with a dense canopy and also to an adjacent area of the same crop but after the canopy had been artificially cut down. “These trials with Kerb Flo 500 have shown that a full oilseed rape crop canopy at time of application makes no difference at all to final levels of black-grass control. The same will apply to AstroKerb for control of black-grass, so no need to be concerned,” says David.
“However we do need soil temperatures to have gone down to 10ºC and falling at 30cms depth, so that the actives are broken down more slowly and the herbicide has sufficient persistence for the weeds to accumulate a lethal dose. Good levels of soil moisture help distribute the herbicide in the top few cms of the soil. Germinating grass-weed seed should not come from any deeper than 5cms, as the black-grass would then be germinating from below the zone where the propyzamide concentrations are high enough to give good levels of weed kill. Soil conditions in many areas are now right for applications to get underway,” advises David.
David urges growers and advisors to check their local conditions using the new web-based Postcode traffic light tool on the Dow main web site, the LifeCycle web site and also on Farming On-Line.
“In addition to the on-line traffic light system, the usual information on soil temperatures and soil moisture deficits is on our web site or is being sent out to advisors and growers. It is important that AstroKerb is given the best chance to work well. If application conditions are right, farmers can expect levels of black-grass control from AstroKerb or Kerb Flo 500 frequently in excess of 90%, a level that very few herbicides are currently achieving in any crop.”
He reminds growers that careful Stewardship of residual herbicides in rape is vital to ensure long term availability of these herbicides.
