Low dormancy can beat blackgrass

Growers have the chance to get blackgrass control off to a flying start this autumn after HGCA-funded research confirmed dormancy in seed samples was low.

A hot, dry June/July has resulted in a 53% average germination for the 37 samples tested across the country.

That is similar to the levels found in 2001, 2003 and 2005, which were also warm, dry summers.

Germination levels in 2002 and 2004 were much lower.

The results mean blackgrass should be quick to germinate this autumn, if there is adequate moisture.

That is not likely to be a problem after the recent rain almost everywhere, ADAS weed scientist James Clarke notes.

Indeed he has already found emerged blackgrass both in stubbles and standing crops.

“Some of it is quite big.”

It means there should be a good chance to maximise germination before drilling and spray off emerged plants with non-selective herbicides to cut the burden on higher-resistance risk selective products.

Ideally, growers should employ shallow cultivations to keep this year’s seeds close to the surface, he says.

“The deeper growers cultivate the more likely they will have seeds from other years, which might have longer dormancy.”

While the effect of low dormancy on germination later in the season is less well understood, Mr Clarke says it is likely to mean pre-emergence herbicides being even more important this season because plants generally will emerge earlier.

“Hitting it hard and early is the right strategy.”

That also goes for post-emergence sprays, he suggests.

“Emergence is likely to be less protracted, at least from this year’s seed, so I expect post-ems to come earlier.

They certainly ought to be an autumn rather than a spring strategy.”

mike.abram@rbi.co.uk