Weed Biology

Understanding weed biology enables more effective management

A weed is a plant in an undesired place. Weeds can often compete with crop plants for nutrients and resources and/or harbour and spread pests or diseases which infect or degrade the quality of crops. Although many weeds have undesirable consequences they can also provide a key ecological role.

Common weed problems

Cleavers in oilseed rape

Cleavers in oilseed rape

Cleavers have long caused problems to oilseed rape growers, due to the competitive nature of the weed and the way it can grow across the canopy late in the season.

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Mayweed in oilseed rape

Mayweed in oilseed rape

Mayweeds are common and high profile annual or hardy-annual composite weeds.

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Poppy in oilseed rape

Poppy in oilseed rape

Poppies are as competitive as grassweeds and mayweed.

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Brome

Brome

Bromes in recent years have become more widespread.

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Ryegrass

Ryegrass

Ryegrass distribution is more widespread and significant where grass leys form part of the rotation.

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Wild-oats

Wild Oats

Wild oats are a competitive grass weed.

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chickweed

Common Chickweed

Common chickweed is found all over Ireland.

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Mayweed

Mayweed

There are several widely distributed species including Scented Mayweed, Scentless Mayweed and Pineappleweed.

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Volunteer beans

Volunteer Beans

Volunteer beans compete with establishing winter cereals in the autumn. Volunteer beans can also cause problems for contact graminicides as large bean volunteers can shade grassweeds and limit contact.

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Cleavers

Cleavers

Cleavers infestations have the potential to cause very considerable crop losses.

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Broad-leaved weeds

Broad-leaved Weeds

Broad-leaved weeds in arable crops.

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Nettles

Nettles

Grass yield / grazing is lost mainly by competition from nettles for nutrients, light and moisture, but also from stock refusing to graze close to nettles.

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Thistles

Thistles

Thistles compete with grass for space, light, nutrients and water, and they are unpalatable to stock.

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Docks

Docks

Docks are the most pernicious and damaging of all grassland weeds.

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Ragwort

Ragwort

Ragwort poses a serious threat to livestock health, left unchecked it can quickly spread and reduce available grazing.

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Buttercups

Buttercup

Creeping buttercup is often a severe problem in horse paddocks, where close grazing tends to open the sward.

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