Three pronged attack protects forage brassicas

Effective pre-emergence weed control is key to getting forage brassica crops off to a good start.

Dr Lauren Jones, UPL Regional Manager Central South Island, says forage brassicas are a hugely important winter crop, contributing 5-20% of feed in Canterbury alone.

“But weed pressure can result in yield losses of up to 60%.”

She recommends a three-pronged attack.

“While all actives have their particular strengths; the combination of three products with four actives — Merit, Monarch, and Major — give you really good weed control pre-emergence and they’re compatible.

“Once the crop canopy closes there’s usually no problem but it’s important to get it to that four to eight week stage.”

Brassicas are also important in Southland.

UPL Regional Manager Otago and Southland Greg McIntyre says a big investment goes into getting them right, and they require heavy inputs.

For pre-emergence weed control on swedes he recommends the combination of Merit, Major and Monarch, with Monarch also used as a post-emergence back-up.

He says it’s also vital to monitor the paddock and consider its history.

“It can be two weeks from a potentially good crop to disaster. If not controlled early, then salvaging crops post-emergence can turn into a nightmare.”

Like Jones, he emphasises looking to the future of the paddock and consulting field reps or agronomists.

“You don’t want weeds dumping seeds that will impact the next rotations. Farmers always have to be looking a couple of years’ ahead.

“It’s not just the current season’s forage brassica crops that are at risk. Weed seed banks can build up quickly in the soil. That threatens future crops and long-term production outcomes.”

The power of the three herbicides combined is firmly grounded in science.

Merit (alachlor, Group 15) controls a range of certain annual broadleaf and grass weeds in forage brassicas.

Proven and effective, Merit extends the weed spectrum in a pre-emergence application.

Major (clomazone, Group 13) is a residual pre-emergence herbicide controlling a wide range of annual broadleaf and grass weeds in forage brassica crops.

It provides outstanding control of problem weeds such as shepherd’s purse, chickweed and cleavers.

A residual herbicide, Major is taken up through roots and emerging shoots of weed seeds. It has little effective contact action and must be applied before weeds and crops emerge.

Monarch (clopyralid and picloram, Group 4) is a specially formulated herbicide for pre-emergence and post-emergence weed control and tread the balance between crop safety, efficacy, and affordability.

Containing twice as much clopyralid compared to some other herbicides on the market it means there is no need to add extra clopyralid to the tank mix.

Lauren Jones says with a comparatively low rate of picloram in Monarch the potential for residual effects on clover is reduced.

“That makes Monarch a highly flexible tool for pre-emergence weed control.”

Greg McIntyre also recommends Unison as the adjuvant of choice with Major, Monarch and Merit for pre-emergence weed control.

Trial work has consistently demonstrated improved efficacy when Unison is included.