Widening weed control options this autumn

Farmers are having to cope with serious weed control problems this autumn, following the legacy of poor weed control last season, and yet they have fewer and fewer options to use. With the loss of IPU and trifluralin, the continuing rise in weed resistance, restrictions in dose rates and complex sequencing, wheat growers are looking for alternative options to control the most competitive and yield-damaging species of grass and broad-leaved weeds.

If we look at all of the active ingredient options we have in the autumn, you can count them on the fingers of both hands chlorotoluron, DFF, flufenacet, flupyrsulfuron, iodosulfuron/mesosulfuron, pendimethalin, prosulfocarb, triallate and flumioxazin (FMX). This set of actives all have their own strengths and weaknesses and so will need combining in a programme, if good levels of weed control are to be achieved this coming year. But it is not that straight-forward as many of these herbicides have significant restrictions in their use – for example chlorotoluron has varietal restrictions and potential risk to water. DFF has limited grass-weed activity and a reduced broad-leaved weed spectrum. Triallate is currently only in granules and has some application difficulties and any ALS inhibitor is restricted to one application per target weed per crop. Weed control certainly doesnt get tougher than this. But what is certain is that every remaining active ingredient needs to be integrated into a programme, not just to control the range of important and competitive grass and broad-leaved weeds adequately, but also to maintain the activity of the limited range we have for a few more years yet, says Dr. David Stormonth, Technical Manager for Interfarm UK Ltd.

Sold as SumiMax or Digital, FMX (flumioxazin) is being put forward as a useful and valuable option to consider this autumn, as it offers exceptional control of many difficult broad-leaved weeds as well as good control of annual meadow-grass and some useful activity on black-grass. FMX can be mixed with a range of grass-weed herbicides, including Defy (pre-em only), Liberator or chlorotoluron, as well as being sequenced with any other herbicide or group. Having no following crop restrictions or following cultivation issues makes it a flexible herbicide to use in weed control programmes, says Dr. Stormonth.

David explains that black-grass will be a major headache this autumn as its control was so poor last season. When it comes to black-grass control, there are three possible lines of defence pre-emergence, early post emergence and late post-emergence. Growers need to plan their defence strategy by building up a planned sequence of herbicide treatments. In Defence Line 1, the pre-emergence timing, three useful herbicide options to start the weed control battle would be 100 mls/ha of flumioxazin mixed with either 0.6 l/ha of Liberator or with up to 3500 gms a.i./ha of chlorotoluron or with 4 kg/ha of Defy. Alone flumioxazin pre-emergence offers between 30 to 40% control of black-grass, but when mixed with other herbicides, the combination gives an excellent and additive black-grass control – a good start to any black-grass control programme.

The second line of defence is early post-emergence when black-grass is still small and at the 1-2 leaf stage. These treatments should complement any earlier applications and build up a defence using products with different modes of action and with both residual and contact activity. FMX fits well as it has strong contact activity as well as residual activity and it from a completely different group, the PPO inhibitors in the HRAC group E. Here FMX can be used alone as a holding spray or can be mixed with chlorotoluron or Liberator for improved grass-weed control. Crops need to be reasonably hardened to reduce any risk of foliar spotting.

The final line of black-grass defence is applied either at the end of the autumn or early winter and there is just the one option based on iodosulfuron and mesosulfuron. Here you need to make sure that any herbicides you have used beforehand are OK to use in sequence with this ALS inhibitor. Reducing black-grass levels in the first 2 defence lines will make it easier for the third defence line to work better.

Dr. Stormonth also advises that FMX is a very useful option for annual meadow-grass control, either pre or post-emergence. Trials and commercial use show that it performs very well on annual meadow-grass, on average 95% control, and much more consistently than IPU ever did. FMX has a very low rate of use too, minimising any risk of getting into water courses. For annual meadow-grass, FMX can be used alone or mixed with chlorotoluron at 500 gms a.i/ha or with Liberator at 0.1 l/ha. With just one autumn treatment and you can spray and then close the gate.

Another significant advantage of FMX is its excellent broad-leaved weed control. In trials applied early post-emergence, FMX gave 100% control of charlock, chickweed, fumitory, field pansy, groundsel, ivy-leaved speedwell, mayweed and red deadnettle, 99% control of cleavers, common field speedwell and Shepherds purse and 98% control of poppy. I cant think of any other wheat herbicide that performs to this level, he reports.

Dr. David Stormonth urges growers to widen their weed control options this season by integrating FMX into their autumn programmes and, by doing so, they will benefit from good, cost-effective control of a wide range of weeds. The cost of FMX has been adjusted this season to make it even more cost-effective. Its an option you wont want to ignore.

SumiMax/Digital contains 300 gms ai/litre flumioxazin, formulated as a white, non-staining, easy-to-use suspension concentrate, packed in a 500 ml pack. Recommended in winter wheat, it can be used pre or post-emergence up to before GS 15 for the control of a wide range of broad-leaved weeds, including charlock, chickweed, cleavers, common field speedwell, common poppy, field pansy, fumitory, groundsel, ivy-leaved speedwell, mayweed, red deadnettle and Shepherds purse, and grass-weeds, including Annual meadow-grass and loose silky bent. It is recommended at 100 ml/ha in 200 litres of water, with one application per crop. It has residual and contact activity. It is compatible with a wide range of autumn products, but should not be mixed with any adjuvants or with pendimethalin products. It can be sequenced with any product including sulphonylureas, but a 14 day interval should be allowed. Dont forget the use of a proprietary tank cleaner before and after spraying to thoroughly clean all spray equipment, including booms, pumps, filters and lids.

Flumioxazin is available as SumiMax and Digital, supplied by Interfarm UK Ltd.