The 1^st of October is the date when the decision support system for ASTROKerb and Kerb Flo 500 starts and it is also the date according to their labels after which these residual herbicides can be applied if and when conditions are correct. The Ready Steady Go traffic light weather system is available 24/7 on the Dow AgroSciences main web site (http://uk.dowagro.com/kerb-weather-data/-) and also on the Farming On-Line web site. ADAS Crop Notes will also be promoting it.

The traffic light system indicates, down to individual postcode level, when soil temperatures are getting close to the optimum for the application of these post-emergence residual herbicides. Peter Waite of Dow AgroSciences says that this system has been enhanced this year to produce even more accurate results. “This year emoji’s have been added for wind and rainfall to give a more complete picture. We want the system to be more accurate and user friendly for growers and advisors.”

“The concept of the traffic light system is very straightforward. Growers enter their postcode and the system lets them know whether conditions are getting close to the optimal for applying ASTROKerb (propyzamide and aminopyralid) or Kerb Flo 500 (propyzamide); if the traffic light shows red, soil conditions are not right so don’t apply these herbicides; if amber, conditions are getting closer, so get set to apply and if green, conditions are close to becoming right. The system is not a definitive go/don’t go but a strong indicator for growers to look carefully at conditions for a particular field or farm.  The system is simple to operate, but there is a lot of technical analysis behind it,” explains Peter.

“To optimise ASTROKerb and Kerb’s performance, there are three areas to consider – soil temperature, soil moisture and weed seed depth. Soil temperatures must be cooling - around 10ºC and falling. At cooler temperatures the herbicide breaks down more slowly and so its activity lasts longer throughout the weed germination period. The half-life of propyzamide at 10ºC is around 100 days whereas at 15ºC the half-life falls to 60 days.

It is important that weeds particularly grassweeds such as black-grass and rye-grass are able to pick up a lethal dose of propyzamide. Both these weeds have become difficult to control in cereals and if propyzamide is given the best conditions to work, it can produce levels of control of over 90%. Propyzamide has no known resistance despite being used for many years and because it works in a different way to any cereal herbicide, its use in rape forms an important anti resistance strategy,” says Peter.

“Soil moisture distributes residual herbicides evenly in the top few centimetres of the soil. Soils must not be waterlogged or saturated, however. Care must be taken to avoid any risk of contamination to water and importantly, all aspects of good stewardship must be adhered to. Maintaining stewardship of residual herbicides in rape is important to ensure the long term availability of these herbicides and every manufacturer, agronomist and grower need to take on their own responsibilities.”

“Finally germinating weed seed should not come from any deeper than 5 centimetres as the black-grass would be germinating below the zone where ASTROKerb and Kerb Flo 500 concentrations are high enough to give good levels of weed kill,” he advises.

ASTROKerb and Kerb Flo 500 have the same conditions of application and the same wide application window of four months, starting from the 1^st of October through to the end of January.  “Don’t forget that the crop needs to have three leaves. ASTROKerb delivers the same weed spectrum as Kerb Flo 500, with the addition of mayweed species and common poppy. We would expect activity on sow thistle and groundsel too. ASTROKerb has obviously caught the imagination of many growers as more of this herbicide is being used year on year. Perhaps growers see the appeal of a post-emergence herbicide especially with Cabbage stem flea beetle and high risk pre-em co formulations. With ASTROKerb and Kerb you know you have a crop that is worth keeping, before you invest in the expensive weed control,” he says.

“The usual weather data reports for advisors and growers will also be on the Dow AgroSciences web site or sent out directly. These weather reports carry information on getting the best from propyzamide-containing herbicides plus graphs of soil temperatures and moisture deficits over time in several locations. Kerb Flo 500 and

ASTROKerb should be given the chance to work well, as many growers are using rape as a true break crop where weed seed populations can be reduced,” says Peter.

In my experience, says Peter, conditions are normally optimal for application around or after Bonfire night, 5^th November.  “Kerb Flo 500 and ASTROKerb may be applied in frosty conditions but avoid application onto frozen ground where subsequent rainfall could result in run-off into watercourses.”