Perennial pastures can become overrun with weeds if left unchecked. Dry summers, wet winters, insect attacks, poor fertility, and overgrazing cause the death of desirable pasture plants and create gaps for weeds to colonise. These weeds compete for light, space, moisture and nutrients, and must be controlled.

As I walk pastures around the country in the early spring as well as driving and looking over the fence, I notice more pastures infested with weeds such as buttercup and dock. These two weeds can cause a large amount of competition to perennial pastures and if not addressed, will force you to renew your pasture earlier than desired due to poor performance.

Most people forget they have these two weeds until they see paddocks covered in yellow buttercup flowers or tall ugly dock seed-heads standing above the grazing platform. Often by then, it’s too late to do anything effective about them and stay relatively clover-safe.

Normally, the best time to use broad-spectrum herbicides such as 2,4-D for weed control in established pastures is during late autumn or early winter. For these two weeds however, 2,4-D is not the correct product or timing. Early spring, when weeds are actively growing, is the best time for some other selective chemistry. A range of herbicides are available for use in established pasture and if used correctly, they should give a high level of weed control with no damage to pasture grasses. Some also give minimal damage to clover species.

The timing of the sprays is when soils have just started to warm up and when you see the first signs of buttercup flowers. If docks are present, the sprays should also be applied when the first new spring leaves of the docks begin to unroll. Often, finding the best time for an application requires a compromise between these two indicators.

When using herbicides, the clover content of the pasture must be considered as this affects your product, selection and timing. If the clover content is very low or non-existent, then more robust chemistry can be used to kill tough weeds and any clover. It is safe on grasses and clover can be added back later. If there is a good amount of clover, then we must use “softer chemistry” that is either safe to clover or less damaging to clover. There will be pasture growth suppression the warmer the conditions are at the time of spraying, so don’t delay too late into spring.

Walking your paddocks and identifying what weeds and pasture species are present helps with product choice and timing. Some weeds such as dock and buttercup, are best controlled in the early spring whereas others like thistles, especially Californian thistles, are best sprayed at the hardball stage in December, January, and then again in March.

Contact your local PGG Wrightson Technical Field Representative to prepare a crop protection programme this spring.