Black-grass control may have been good last autumn says Richard Peake of Harlow Agricultural Merchants (HAM), but he suggests that "growers can't take their foot off the neck of black-grass, even for a second, because if we do we all know we will  have a huge problem in the future."

"The combination of low dormancy from black-grass seed shed in summer 2010 combined with the very wet August gave very high levels of black-grass germination even before the end of harvest. The conditions allowed multiple stale seedbeds which were extremely effective."

"Also, pre-emergence (pre-em) herbicides were applied in almost ideal conditions giving really good control of black-grass in many areas. So much so, the amount of Atlantis growers had to apply in Essex, for example, fell by 25%," he adds.

He warns that "we all need to avoid what happened in the preceding two to three years of horrendous black-grass control resulting from poor accuracy of pre-em applications and the post-emergence (post-em) herbicides becoming less effective. In some parts of Essex black-grass was so bad that wheat yields dropped to 0.5 t/acre and caused very high black-grass seed return exacerbating an already dreadful situation.We must do all that we can to avoid returning to these years."

At HAM six years worth of trials have been conducted based on blackgrass strains from local farms; typically in Essex these are populations that are partially resistant to Atlantis. HAM had trials looking at various pre-ems alone as well as stacked pre-em treatments to see how the herbicide programmes performed on different levels of resistance. The programmes were all based on flufenacet.

"Over the past 5-6 years in our trials on chalky boulder clays Crystal has outperformed Liberator by an average of 10-15% and therefore has been the basis of the black-grass control programmes. However, with Altantis resistance increasing in recent years, the flufenacet based treatments are becoming slightly less effective against the most resistant RRR strains of blackgrass. Straight sprays of Crystal or Liberator are no longer sufficient for the most difficult to control black-grass populations and the benefit of residual stacking is clear."

The 2009 trials show that the addition of DFF (0.25 l/ha) to Crystal, substantially boosted control by 10-15%. In 2010 the overall level of control increased to 60-70%." He adds that the bonus of DFF to Crystal tank mixes is that broadleaved weed control has also been extremely good.

"Walking around in the trials and commercial applications this spring we found extremely low levels of black-grass and extremely low levels of broadleaved weeds including cleavers. Adding in the DFF in the autumn negated the need for a spring cleaver spray and cost the same."

"In 2010 where we had very bad black-grass, we used residual stacking of Crystal + Buckler (DFF + CTU) giving us four active ingredients to tackle the black-grass which has also given very good control. However, growers need to be a little cautious because 35% of varieties in the area are sensitive to CTU. Also, growers need to check CTU status for new varieties; for example Santiago is sensitive to CTU."

Avadex granules were included pre-em for the first time in trials in 2010. "We achieved a surprising 75% control. These results may be slightly higher than in a commercial situation, but the interesting thing was that this level of control did not vary between the different resistance strains of black-grass. Even where black-grass is particularly bad, a sequence of Avadex granules followed Crystal + DFF was a top notch programme which could be used very effectively this autumn."

He reminds growers that if they have their black-grass tested "the results can be very accurate for Atlantis, Laser and Topik; however the test results for the residuals, flufenacet, prosulfocarb and pendimethalin need to be treated with more caution as they are done in glasshouse situations where the active growth usually finishes in December, whereas in a field situation herbicides grind away at the black-grass over several winter months. This death by a thousand cuts is particularly noticeable with pendimethalin, due to its longer lasting activity compared to other active ingredients, and doesn't happen in the glasshouse."

He says that for growers who struggle to apply pre-ems, because of their cultivation or drilling approach, "treatments of Crystal and Crystal + DFF applied when black-grass is just visible and wheat is at the one leaf can still give very good control. But timing must not be delayed. If you delay applications to when black-grass is at one leaf [a week after tramlines are visible], the control will really start to fall away."

He reiterates his earlier point that it will be very important not to rest on our laurels from the good control we achieved last season. "The approach this autumn mustn't be any less than we did last autumn. The black-grass battle is not over. I've been battling it for 40 years and I have still not won."