Experts warn growers not to delay pre-ems this season

Delaying pre-emergence herbicide treatments until cereals have emerged is a risky strategy this year, warns Masstock’s technical manager Clare Bend.

“In most situations we are advising growers to spray within 24-48 hours of drilling with flufenacet based products [as in Crystal], which not only gives the best control through reduction of the Black-grass population before Atlantis is applied, but also plays an important part in an anti-resistant strategy.”

However, there is a move from some growers towards waiting until drilling is complete and then spraying when the cereals are at the peri or post-emergence stage, she adds.

Crystal can be used from pre-emergence right through to post emergence with no cut off in the middle, provided the seed is covered by 32mm of soil.

“The additional driver behind this is that growers are looking to save a pass, so by going at the 1-leaf stage and adding in the BYDV spray they may not have to make another application.”

And this, says Ms Bend is a dangerous strategy in a year where low dormancy is causing Black-grass to emerge quickly and early.

In Masstock trials delaying the pre-emergence application until peri-emergence or 1-leaf stage causes a drop off in control from about 70% to 50%.

This doesn’t mean growers should exclude Crystal, says BASF’s Phil Brown. “There is a tail off in activity when applied later, but control levels can be improved by adding in other products.

“Growers with crops at the peri-emergence stage with small amounts of Black-grass should still use Crystal alone, but if populations are larger or the Black-grass is at the 1-2-leaf stage we recommend adding in IPU or Lexus to raise control levels.”

And if the Black-grass is more advanced, up to the 2-3-leaf stage, Crystal can be mixed with Atlantis.

But growers must be aware that using Lexus or Atlantis at this stage will limit the option of using other herbicides later in the season due to sulphonylurea sequencing restrictions, adds Mr Brown.

In Rye-grass situations Crystal offers more post-emergence activity than on Black-grass, which gives growers slightly more flexibility if spraying is delayed. And there is still an option to include chlorotoluron on tolerant varieties, says Mr Brown.