Getting broad leaved weed control right this spring
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Authored by Alister McRobbie, Cereal Herbicides Category Marketing Manager
As winter gives way to spring, one of the first considerations on arable farmers’ minds is getting back to fieldwork. Planning a robust herbicide programme should be a top priority this spring.
Learnings from the past three years have shown that the window for applications can open as early as February or as late as April. This spring, saturated soils following a very wet winter will delay growers’ ability to get on with the job, which makes preparation – including getting the right chemistry in store and ready to go - all the more important.
Getting a good grip on the weed burden that is present is an important first step before deciding on herbicide investment. For some farmers, they may already know which weeds have carried over through the winter.
This season, weed pressure will pose a greater threat. This is because the persistent autumn rain will have washed out any residual herbicides from the soil profile. And there will also be spring-germinating weeds to care of, especially where spring cereals are sown.
In winter crops, the main broadleaf yield robbers include cleavers and cranesbill, which are likely to come through strongly after the winter. Chickweed, groundsel, brassicas and some umbellifer species should all be tackled while they are small. Poppy, which is subject to ALS resistance in some parts of the country, can be tricky to control. In wheat, only 12 Poppy plants per square metre can reduce yields by 5% in winter wheat.
The objective is to control the weeds while they are small to stop them competing with the crop for space, light and nutrients, and to give the chemistry the best chance of delivering a good result.
Cereal crops planted late after potatoes or sugar beet are likely to have had little or no residual herbicide programme. The weed spectrum can be different in these situations, with spring germinators fat hen, orache, black bindweed and black nightshade often present.
Scottish barley growers will be all too familiar with the prevalence of fumitory which can cause significant issues if not controlled before soil temperatures rise and crops begin to motor through the growth stages. Farmers growing spring barley outside of traditional spring barley growing areas due to the wet winter weather will need to plan for a robust braod-leaved weed herbicide programme.
Unfortunately, there is no silver bullet product to cure all weed control problems.
Under normal circumstances a pre-emergence application followed by a contact spray will have laid a solid foundation for the spring season. However, 2023’s extremely wet autumn neutralises the effect of these herbicides.
Corteva’s Arylex active molecule has become a mainstay of any spring broadleaf weed herbicide programmes. Arylex’s key point of difference from traditional chemistry is the ability to perform extremely well in cold and fluctuating temperatures. This makes the molecule a great fit for early spring, while sulfonylurea chemistry may struggle to achieve good control of some weed species, especially larger poppies.
And there is a yield benefit to consider with earlier applications.
Trials by Corteva have shown a 1.75t/ha yield benefit in winter wheat by treating crops with Arylex.
The study, carried out at Corteva’s Wellesbourne site in Warwickshire, showed chickweed, poppy, cranesbill and cleavers were present in both trials and were totally controlled by Zypar (Arylex active + florasulam) at 0.75 litres/ha. The trial treated on the 24th of February yielded 9.33t/ha while the plot left until the 24th of April yielded 7.58t/ha, showing the benefit of early application where possible.
But the opportunity to take out key problem weeds early is not always there. In this instance, Arylex chemistry has excellent tank-mix compatibility which is essential in a season where complicated sprayer loads will be the norm.
Pixxaro and Zypar both contain Arylex and are contact-acting herbicides which can be applied all the way through to growth stage 45 in winter and spring cereals. Zypar is also approved for use on winter oats at 0.5 litres/ha. Arylex controls ALS-resistant poppy populations as well as cleavers, cranesbill, chickweed, mayweed, fat hen, fumitory and charlock.
Applied at the T0 fungicide timing, Arylex can remove competitive weeds early in a single pass. Growers who wait until the T2 fungicide timing, can use Arylex chemistry to mop up weeds that have escaped treatment earlier in the spring, as well as clearing out late flushes of cleavers and black bindweed which may come through.
Tank-mixing Arylex herbicides with sulfonylureas or phenoxy herbicides is often necessary to control a wider spectrum of broadleaf weeds. In spring barley, an SU partner such as thifensulfuron-methyl plus metsufuron-methyl, will broaden the scope of the application to pick up polygonums, umbellifers and brassicas. The activity will depend on the weed size. Zypar is more active on brassicas than Pixxaro because it contains florasulam rather than fluroxypyr. Umbelliferous weeds – bur chervil and cow parsley for example – can be controlled with the addition of an SU such as Harmony M if Zypar cannot be applied when the weeds are small.
For more information on using Arylex active this spring, please contact us via the Corteva helpline on 0800 689 8899 or visit www.corteva.co.uk.