Conditions are ideal for Atlantis application in many areas and growers with blackgrass at one-leaf or more should be getting ready to spray, say experts.

Blackgrass is actively growing and it’s a good time to apply, says Mark Hemmant, technical manager for Agrovista. “It’s much more effective to spray Atlantis in the autumn and we have seen good levels of control up to Christmas, in some seasons.”

But variations in drilling dates this autumn mean wheat crops are at different stages. “Some earlier-planted crops have large, actively-growing blackgrass populations, but others are only just being planted.”

Atlantis should therefore be applied when blackgrass is at one to three leaves and soil temperatures are high enough for the weed to be actively growing, rather than calendar date, he adds.

Efficacy of pre-emergence herbicide applications has been a mixed bag, but even where control has been effective some fields still have high populations, putting increased reliance on Atlantis, he says. “Because there was so much blackgrass in the first place, good control from pre-emergence herbicides has still left a lot of plants.”

Bob Mills, technical manager for Frontier, says mixing a residual product with Atlantis will improve activity and tackle weeds emerging after application.

Product choice will depend on the actives used at pre-emergence, but pendimethalin or prosulfocarb are obvious choices, he says. “If you used Liberator at pre-emergence you have still got a big slug of pendimethalin to use before you reach the 2000g/ha active ingredient threshold.”

Flufenacet and Auxiliary can also be used as partners and Firebird has had a label change this year allowing two applications to be made to the same crop, as long as they are a minimum of six weeks apart, says Mr Hemmant. “Auxilliary is particularly effective as it gets later and temperatures drop.”

Correct application is also crucial for optimising efficacy, he says. “At this stage 100 litres/ha is a good water volume to use along with nozzles at the finer end of the spectrum. Air inclusion nozzles should be avoided and jets should be angled forwards.”

Carbetamide going on early

Carbetamide is being applied to some oilseed rape crops with advanced blackgrass before soil temperatures drop below the 10C threshold.

Many early-planted oilseed rape crops have large blackgrass populations that could become uncontrollable if propyzamide and carbetamide applications are left until soil temperatures drop, says Mr Hemmant. “The concern is if we wait too long blackgrass will be very deep-rooted and difficult to control.”

Applying a full rate of Crawler now can be beneficial, particularly where crops have been established using shallow minimum tillage techniques, he says. “Where blackgrass roots are shallow it is not as important to have the persistence you get with colder temperatures.”

• Go to www.fwi.co.uk/application for more blackgrass application advice.