US growers tackle weeds with herbicide-tolerant beet

Monsanto has developed glyphosate tolerance in sugar beet using the agrobacterium strain ‘CP4 EPSPS’. In simple terms, if glyphosate is applied to a beet plant containing the resistant strain, the plant will survive.

Speaking at the 2009 Raymond Hull Memorial Lecture at Broom’s Barn research centre in Suffolk, Dr Mohamed Khan, a sugar beet specialist at the University of North Dakota and Minnesota, said weeds were a big problem for beet growers in the US.

As in the UK, conventional control with herbicides, such as desmedipham and triflusulfuron, has been normal practice. With the RR sugar beet, weed control has been excellent.

“The real benefit of RR sugar beet is the flexibility it brings to farmers in applying glyphosate. Timing with the herbicide is less critical,” said Dr Khan. “Most growers will complete two applications of glyphosate in a season – they drill in late April, spray twice in the season and there is no competition from weeds.”

RR sugar beet comes with a ‘technology fee’, typically $158 (£111) per hectare.

Cost comparisons show little overall difference when total input and operational costs are considered for both growing systems – around $50 (£35) per ha between the two.

“Studies have found the reduced cost of herbicide sprays and number of passes in the field in RR sugar beet will almost make up for the extra input cost of the technology fee,” said Dr Khan.

Yield comparisons have also been similar – there is no indication that the H-T gene is inhibiting yield.

The United States Department of Agriculture (USDA) is facing a legal challenge from the Organic Seed Alliance for cross-contamination of organic crops with RR crop pollen, but it was unclear how successful the challenge would be.

Dr Khan said there were other challenges to overcome such as weed resistance to glyphosate, which was already a problem, as well as dealing with volunteers from other H-T crops such as RR soybean and RR corn when in the same rotation as RR beet.

“While it is straightforward to remove these with a different herbicide, we are trying keep costs down for growers as much as possible – they already have a technology fee to pay,” he said.

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