With recent rain spurring onblack-grass growth and development, now’s the time to check populations and considerpatch spraying with glyphosate advises Farmacy agronomist, Ryan Hudson.
Black-grass is flowering across muchof the country, increasing the urgency with which growers need to mappopulations and, if necessary, take action to prevent seed return.
gOnce black-grass flowers, it is quickto set seed and shed,h says Mr Hudson. gBy the time wefre at seed formation,therefs a chance that glyphosate applications are too late; seed may still beviable when it hits the ground.h
Bayer CropScience trials fieldofficer, Roger Bradbury agrees. gGrowers have only a couple of weeks to getfields walked, mapped and where appropriate, sprayed off.
gPatch spraying is a drastic measure,but a useful one that aids resistance management and yield preservation in subsequentcrops.h
There are a number of cases where MrHudson will be advising growers to sacrifice some crop to get on top ofblack-grass. gWefve a couple of winter barley crops where wefve poor controland some wheat crops where resistance, poor herbicide coverage or simpleapplication misses are to blame.
gIn all these cases, if theblack-grass is left, the combine and cultivator will spread black-grass seedfurther across the field and we will have a much bigger area and population todeal with next year.h
Mr Bradbury and Mr Hudson emphasisethe need to crop-walk with map and pen in-hand.
gHaving an accurate picture of howmuch black-grass youfve got and where it is, year-on-year, is really useful,hsays Mr Bradbury. gWhile you can get a feel for whatfs out there from the cab,nothing beats crop-walking.
gWhere post-ems have been applied inthe spring there is a chance black-grass has been stunted rather than killed -seed heads could be developing just out of sight below the crop canopy, h headds.
gThe information gathered can be usedfor identifying trends in the rise and fall of populations, the efficacy ofcontrol strategies and, most importantly at this time of year, whether or notto spray off the worst areas with glyphosate.h
Mr Hudson says black-grass canindicate underlying problems like poor drainage and soil structure. Mappingthese areas allows him to investigate and correct such problems after harvest.
gBlack-grass maps can be overlaid onsoil type maps and used when variably drilling – increasing the seed rate onknown black-grass areas improves the competitiveness of the crop.
gMapping can identify where we shouldprioritise stale seedbeds, scratching the surface immediately after harvest toget a flush of black-grass before any deep cultivations.h
gWe cannot rely on herbicides alone,we must use cultural controls,h he says. gBy mapping these problem areas now,when they are easy to see, we can be more focused with our management in thefuture.
Finally, Mr Bradbury points out thatgrowers should not be too disappointed even where fields look dirty. gIt is easy to forget how much black-grass istaken out with a full control programme. With trials it is easier, there isoften a direct comparison but in field it is harder to see what has beenachieved.
gControlling black-grass is a enumbersgamef and where youfve a high population to start with, it can be scary howmuch black-grass remains even when you achieve over 95% control.
gAchieving 98% control of a moderatepopulation, 250 plants/m2 for example, still leaves five plants/m2.h