Ragwort, thistles need action

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Invasive and noxious pest plants such as ragwort and thistles are obvious on a number of Tamahere properties at the moment raising questions about whether some landowners are aware of their responsibilities.

Ragwort flowering

The yellow-flowering ragwort – highly invasive and poisonous to cattle and horses – is one of the more obvious invaders currently as its bright flowers make an appearance from November to April. The purple flowers of plumeless and nodding thistles are similarly signalling their presence.

Tamahere landowners, in what’s known as a total control area, are required under biosecurity law to destroy all ragwort, plumeless thistle and nodding thistle plants on their properties to prevent them flowering.

Controlling Ragwort
Pulling plants out and disposing of them by deeply burying, burning or composting (if no seed heads are present) is an effective method of controlling ragwort. Plants are best pulled at the flowering stage where the roots are much less likely to re-grow. Mowing ragwort is not recommended, as it will encourage the plant to become multi-crowned or to become a perennnial plant, making it difficult to control. Ragwort is poisonous to cattle and horses but not sheep, so stocking ragwort-infested areas with sheep will reduce the number of plants.

There are many effective herbicides that will control ragwort. See here for more detail.

Controlling Thistles
Grubbing plants is an effective method of controlling thistles, provided that they are grubbed at least five cm below the crown and control work takes place before the onset of seed. Mowing (or topping) thistles is less effective as the plant is able to re-grow from the crown. You will need to mow repeatedly to make sure the plants do not reach flowering/seeding stage.

Herbicides also control thistles. The Waikato Regional Council employs contractors and staff to provide practical advice for controlling plant pests. To contact your local Biosecurity Plant Pest Contractor or council staff call 0800 BIOSECURITY (0800 246 732) and follow the voice prompts.

Weedbusters may also be of assistance with information on these and other pasture weeds.

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