SAC tests show Scots blackgrass resistance free

Scottish growers might be able to treat the increasing incidence of blackgrass in their crops with a full chemical armoury, if initial resistance tests prove to be representative of the whole population.

Those tests have found no resistance to any chemical whatsoever, says SAC’s Ken Davies.

“It was to our surprise.

Everyone thinks the blackgrass is coming up with English seed, but if it had, the chances are pretty high that it would have resistance to something.”

Instead the results of tests conducted on blackgrass seed collected at harvest 2004 suggest the populations might be locally evolved.

“Blackgrass does occur naturally in Scotland, albeit it relatively uncommonly.”

So far, only two samples have been analysed, with a further five sent down from harvest 2005, he notes.

“We cannot draw any firm conclusions.

Patches suddenly appearing in the middle of fields are probably more likely to have come via the seed.”

But potentially the resistance-free status is good news, he says.

“If the blackgrass is locally evolved it should allow growers to get started on the right foot.”

Maintaining the susceptible status of the blackgrass should be the primary aim.

“We can learn from the English experience, and use programmes, sequences from different chemical groups, as well as utilise cultural controls.

“It is a bit more expensive to do, but it is worth it.”

Blackgrass in Scotland is not a major problem yet, he acknowledges.

“I know of a few quite serious populations, although most populations are just patches.

But the number of fields being reported is going up.

The warning signs are there – it is better to be forewarned and forearmed.”

The increase in incidence could be down to a number of factors, including the tendency to sow more winter crops, he believes.

“Certainly in south-east Scotland and Northumberland the proportion of winter wheat based rotations has increased over the last five years.

It increases the potential for grassweeds.”

Other factors could be milder winters, increased use of reduced tillage and simply better recognition, he says.