Four warned is forearmed in weed control (From Gazette & Herald)

Four warned is forearmed in weed control

Grass weed control should be at the top of landowners' agendas at the moment. There are four key components to the process you should know to make it a success. This week, Dr STEVE ELLIS, of ADAS, based at The Research Centre, High Mowthorpe, gives his advice on how to keep on top of the problem.

OVER the years there have been many famous foursomes, the Fab Four, The Four Seasons, The Four Tops, The Four Horseman of the Apocalypse and, most importantly, the four components of successful grass weed control.

Of this elite group, I'd wager that the latter is least well known, but with the main period of drilling underway, it should now be top of the agenda.

The first component is effective stale seeded management. The emergence of weeds has been rapid and the low dormancy of black-grass seeds means that they have chitted in large numbers. These must be destroyed by spraying off before cultivation.

Without this, established plants can be deposited a few centimetres down the soil profile from where they can emerge as strong-tillered plants a few weeks after drilling.

The timely use of pre-emergence treatments is the second component for successful control of severe grass weed problems.

With the need to press on with drilling, it is not always easy to apply pre-emergence herbicides at the optimum timing.

If stubbles have been sprayed off crops should have a reasonably clear start, so with the right product early post-emergence may be a better option.

Although some products can be used until the crop is tillering, delaying could mean target weeds become more difficult to control.

To get the optimum performance from any herbicide, it is best not to apply it at the limits of its timing window.

The third component of a good weed control programme is weed suppression by a vigorous crop. This season, good early growth suggests that it could be important in limiting the impact of weeds.

However, where a field is known to have a serious weed problem, it is worth making better use of this autumn's very good stale seedbeds by delaying drilling if necessary.

The final component of efficient weed control is the use of post-emergence treatments, and combining these with those applied pre-emergence.

Ideally, a pre-emergence herbicide should provide effective control for as long as possible, without the need for any post-emergence programme.

However, a follow up is often needed, and in this situation the early treatment should leave a uniformly sized target, avoiding a mix of large tillered black grass amongst a mass of smaller one to three leaf plants. Providing a good quality, even seedbed is the first step towards achieving this aim.

To summarise, it is important to make best use of stale seedbed and drilling the weediest fields should be delayed to allow the maximum germination of weeds.

Plan to apply pre-em treatments as soon as possible after drilling and aim for the best possible tilth.

This will have the benefit of giving better conditions when post-emergence products are applied.

And finally, with very rapidly germinating crops, make sure seeds are covered with at least 32 mm or one-and-a-quarter inches of consolidated soil to meet product label requirements.

Updated: 15:13 Wednesday, October 05, 2005