Reliance on one, single pass herbicide rarely provides the weed control needed for an optimum crop and leaving herbicide application until late in the season allows weeds to establish and grow throughout winter and early spring. As a result, control is often incomplete and, when competitive, the weed population will likely impact on crop yields. Pre�emergent or early post emergent autumn herbicide application is generally the best approach as it takes out weeds while they are small and easy to control.

Successful weed control requires thought and action from crop planning and planting, through to all growth stages. Take the opportunity to remove/control weeds whilst the previous crop is still in the ground. If the crop is a broadleaf crop, control grasses to reduce seed shedding and seed bank buildup.

If perennial weeds are present before sowing, consider glyphosate plus Granstar® and ensure application is at least 7 days prior to cultivation or drilling. This will contribute to the breakdown of weeds and aid in ease of cultivation or drilling.

Bromes – cultural control

Cultural techniques can be employed when brome grasses are proving problematic.

If bromes are confined to the headlands, consider:

• Higher sowing rate in the headlands to outcompete the brome;
• Sowing headland in spring rather than autumn cereals as most bromes germinate in autumn/winter;
• Use of glyphosate and/or cultivation prior to sowing;
• Taking headlands for silage to remove seed heads.

If bromes are more widespread, consider:

Post�harvest burning of previous crop stubble to kill seeds;

Sowing non-grass/cereal crops where specific grass killers can be used;

Sowing spring cereals rather than autumn cereals to allow grass weeds to germinate and then be controlled without restraints from crops.

Chemical options

Firebird® is a registered preâ€�emergent herbicide. It contains diflufenican (DFF) and flufenacet and can be used in both wheat and barley. It must be applied before the end of July to be effective.

It will control:

• Hairgrass;
• Cleavers;
• Annual Meadowgrass (Poa annua);
• Most weeds controlled by Cougar® or diflufenican.

Firebird® does not control:

• Fumitory;
• Brome grasses;
• Weeds growing from root chips.

Follow up options at pre�emergent/early post�emergent stage of the crop:

• Gardoprim® for fumitory control and some ryegrass control (notâ€�registered);
• Gardoprim + Glean® or Sencor® (not registered) for some control over Brome and other broadleaf weeds in wheat. Sencor® can be more phytotoxic to wheat than Gardoprim®.

Follow up options for the early tillering stage of the crop include:

• Ryegrass control: Hussar®, Othello OD®, Simplicity®;
• For control of some weeds growing from root chips: Hussar®, Othello OD®, Glean, Mecoprop;
• For Fumitory control: Mecocorp.

Othello OD® controls Ryegrasses, Poa and Phalaris, plus a range of broadleaf weeds. However, it can only be used on wheat. It is more robust than Hussar® on grass weeds, but has a similar timing.

Alternatively, Hussar® is more robust on thistles than Othello OD®. Either way, both of these chemicals will work better with a preâ€�emergent or early postâ€�emergent herbicide application prior.

Care must be taken when choosing herbicides if broadleaf crops are to be planted after harvest. If applying Firebird®, Cougar® or diflufenican; followed by Othello OD® at the early tillering stage, direct-drilled Brassicas and Clover crops can be at risk. This is because of the high amount of DFF applied to the soil. At full label rates, Firebird® will apply 60g DFF/ha and Othello OD® 50g DFF/ha, giving 110g DFF/ha.

The chemical forms a ‘film’ on the soil surface and has a halfâ€�life in the soil of 15â€�30 weeks, which is where one can run into trouble. Direct drilling brassicas or clover using disc type drills allows the reestablishment of the DFF ‘film’ which can kill emerging brassicas or clover. However, there are no issues when ploughing or thorough cultivation takes place between harvest and planting.

Puma® S and Twinax® control Phalaris and Wild Oats. Twinax® will also control Ryegrass if small. Both herbicides are able to be used in wheat, but Puma® S is not able to be used on barley. The products can both be applied up until the first node stage of the crop.

Simplicity® is an early postâ€�emergent herbicide used to control Ripgut Brome, annual Ryegrass, Wild Oats, and broadleaf weeds in cereal rye, triticale, and wheat. It is not able to be used on barley, oats, or durum wheat. The herbicide is most effective when sprayed within four weeks of a preâ€�emergent treatment, and is able to be used with other broadleaf herbicides where necessary. It should be sprayed on actively growing weed seedlings, from the three-leaf stage up to the first node stage of the crop. Care should be taken not to spray any other ALS inhibitor per crop per season for control of grass weeds, to avoid breeding resistance.

Weed Control in Autumn Sown Cereals has been adapted from information supplied by Pramda Lallu.