Weed control is on the agenda for many growers in the coming days. With the delayed spring and later-sown spring crops, weeds are poised to rapidly grow through their growth stages so spraying early is important.

There has been good growing conditions as of late and spring cereals currently range from emergence to tillering. Growers will aim to apply their spring herbicide at the three- to five-leaf stage.

Broadleaved weeds are particularly important to control due to their competitive nature and known resistance to key herbicide groups. By delaying or missing application timings, the risk of losing yield potential through weed competition increases.

Correct identification of the stage and type of target weeds in a field is essential. Most herbicide applications will be applied by mid-tillering, generally before the target weed has passed the two true leaf stage. Once a weed has been properly identified, then the appropriate herbicides can be applied.

Resistance

Incidences of weed resistance to herbicide groups continues to grow in fields across the country. Poppy, chickweed and corn marigold are some of the key weeds which have known resistance to ALS chemistry.

Careful management and follow-up field visits to monitor their control is essential but proper identification of the weeds remains the first step.

A key method of indenting broadleaved weeds is by looking at their cotyledon(s). These are the first leaves sent out by the germinating seed. The first true leaves which follow after the cotyledons are also key identifying features of the weed.

Here is a sample of 18 common tillage broadleaved weeds and their key identifying features, scroll through the gallery to see the weeds.

  • Knot-grass: the weed has a short, reddish stem. The cotyledons are long and narrow and the first true leaf is long and broad at the tip.

  • Fat-hen: the cotyledons are long and narrow and have a mealy, silvery appearance. The first true leaves are a rounded triangular shape, purplish underneath with a purple stem.

  • Fumitory: the cotyledons are very long, narrow, light blue-green and attached to a tall pinkish stem. The first true leaf is pale green and divided into stalked leaflets.

  • Groundsel: the cotyledons are a narrow, oval shape, shiny on the surface and purple beneath. The first true leaves are teethed, stalkless and a shiny dark-green colour.

  • Red deadnettle: the cotyledons have distinctive notches at the base of the leaf. The first true leaves are hairy, with shallow teeth, branched veins and are oval in outline.

  • Field pansy: the cotyledons are oblong, dark green and slightly notched at the tips. The first true leaf has a broad, rounded tip and toothed margins (Seedtec).

  • Redshank: the cotyledons are lance-shaped and rest on a reddish-crimson stem. The first true leaf is broad, smooth, dark green and tinged with red.

  • Charlock: the distinctive cotyledons are kidney-shaped. The first true leaves have irregular indentations along its margins and a broad, rounded tip with surface hairs.

  • Common poppy: the cotyledons are small, narrow and light green in colour. The true leaves are mitten-shaped and subsequent leaves are lance-shaped, hairy and deeply divided into lobes.

  • Cleavers: cleaver cotyledons are large, oblong in shape, dark green in colour and have a distinctive notch at their tips. True leaves are lance-shaped and are covered with sticky hairs.

  • Corn marigold: the cotyledons are fleshy/waxy, oval-shaped and blue/green in colour. The true leaves are narrow, have several lateral lobes and are glossy and blue/green in colour (Teagasc).

  • Black bindweed: the cotyledons are reddish green in colour, oblong in shape and rest on a crimson stem. The first true leaf is heart shaped and reddish in colour.

  • Common chickweed: the cotyledons are small, light pale green, oval-shaped and pointed at the ends. The first true leaf is broad at the base, long and lance-shaped.

  • Common field speedwell: the cotyledons are distinctively spade-shaped and hairy. The first true leaf is hairy, oval-shaped, pale green and with toothed margins.

  • Common dock: the cotyledons are narrow and long, often deep purple to crimson. The first true leaves are broad, rounded and hairless. Subsequent leaves have long stalks and prominent veins.

  • Hemp-nettle: the cotyledons are large and have backwardly pointing lobes at the base. The first true leaves are veined, hairy, pointed and arise from long stalks.

  • Mayweed: the small cotyledons are oval shaped and stalkless. The first true leaves are very narrow and generally have several, finely divided, deep lobes. (Teagasc)

  • Shepherds purse: the cotyledons are smooth, oval shaped with a short stalk. The first true leaves are usually rounded while later leaves are deeply toothed, lance-shaped and silvery in appearance.

    • Herbicides

    There are dozens of effective herbicides which are suitable for spring crop application from the two- to three-leaf stage right up to flag leaf. Once your weed spectrum is identified then this will assist in guiding product choice.

    Herbicide tank mixes will most likely include an SU, or a mix of SUs, plus a contact or hormone partner. Ally Max or Cameo Max plus CMPP remains a popular choice as the CMPP gives good control of Fumitory, Fat hen Orache and Cleavers. Galaxy or Pixxaro offers a very wide spectrum of control and are particularly useful against resistance weeds. Adjuvants such as Torpedo, Kantor or Solar Plus may be of use where target weeds are small in size and difficult.

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