GM sugar beet helps US growers beat weed onslaught

Blackgrass is an increasing problem in UK sugar beet crops and one long-term option is planting herbicide-resistant sugar beet. US sugar beet specialist Mohamed Khan explains how it has helped the US sector tackle its weed threat.

How big is the US sugar beet industry and where are the main growing regions?

The US sugar beet industry covers nearly 0.5m hectares producing 4.7m tonnes of sugar. About 60% of the sugar beet production is in North Dakota and Minnesota, worth $3bn in just these two states.

There are seven factories covering the two states, all of which are owned by farmer co-ops. Five are owned by the American Crystal Sugar Company, which is an agricultural co-operative owned by about 2,800 sugar beet growers in the Minnesota and North Dakota portions of the Red River Valley.

What are the key challenges facing US beet growers?

Drilling and lifting windows are very narrow because of the short growing season, with crops drilled in early May and lifted six months later in October.

The roots are then lifted and clamped, being transported to the beet factories over an eight-month period from September to May, as it can’t be left in the ground because of the permafrost.

This means lifting is typically carried out starting 1 October (ideally during a 10-day period) and drilling in five to six days. Unlike in the UK, most growers have their own kit (drill, sprayers, topper, harvester and trucks) and don’t use contractors. Therefore, kit tends to be of a large scale, with high work rates.

As in the UK, disease, pests and weeds are other key challenges. For example, cercospora leaf spot alone resulted in $100m (£60m) of losses back in 1998. Growers are managing the disease by rotating chemistry.

But the number one problem in 38 out of the past 45 years of sugar beet growing has been weeds. The US is one of the weediest places on earth, with kochia, common ragweed, giant ragweed, and amaranthus species (wild oats, sow thistles, leafy spurge – these were present in the very early days of farming in this area) being particular problems. The weed population is so high they can take over the crop, therefore, good control is essential for viable crops.

Weed control is also crucial for a smooth-running harvest, as farmers don’t want them clogging up the harvester when lifting in such a narrow window.

How has the arrival of Round-up Ready sugar beet helped growers?

Round-up Ready sugar beet showed good weed control in trials. Seeds became widely available in 2008 and accounted for half of the area in the first season.

Glyphosate is a very effective herbicide and this GM technology has enabled excellent weed control, as well as allowing greater flexibility with herbicide timings.

It resulted in fewer problems when lifting beet, allowing growers to maximise yields. Performance has been good – for example, crops grown by American Crystal growers in 2012 yielded 67t/ha at 19.14% sugar.

GM sugar beet has also allowed farmers in western states, including Nebraska and Colorado, to direct drill the crop into wheat stubble. This helps seedling survival, as you can get damaging 40-50mph winds and stubble helps to protect plants. This approach was impossible previously, as you could not control weeds.

Does GM sugar beet cost more to grow?

Yes - the seed costs are higher for as you have to pay for the technology, but there are some savings with less herbicides needed to be applied. Overall, the Round-up ready crops costs about $80/ha more to grow in the Red river area. But in western states, such as Nebraska, Colorado and Wyoming , production costs have been significantly reduced.

Is there a growing problem of herbicide resistance?

There are more than 400 reported cases involving 150 herbicides and most modes of action, including glyphosate.

Resistant weeds include waterhemp, common ragweed, giant ragweed and Kochia scoparia. The last one is a real concern with glyphosate resistance, as it can rapidly overcome a crop.

Looking at GM crops, there were some areas where the technology worked so well, that some farmers pushed it too hard and the result is weed resistance. They were growing Round-up Ready soya and maize in the same rotation or continuous soya or corn because of favourable prices (not common in the areas where sugar beet is grown).

But there are strategies to control this risk by adjusting the rotation to include GM crops resistant to other actives such as Liberty Link soya, which is resistant to glufosinate. With GM maize, conventional herbicides are used alongside glyphosate, reducing the pressure by allowing rotation of herbicides.

So what will growers be growing in 2020? I see a range of GM crops being grown to reduce resistance, including Round-up Ready (glyphosate), Liberty Link (glufosinate), Round-up Ready Xtend (glyphosate + dicamba) and Enlist Weed Control (2,4-D resistant corn and soya bean) crops.

How widely is GM crops grown and what is the legal situation?

The sugar beet area is 100% Round-up Ready in most areas and it is now starting to be grown in California.

There was a law case back in 2008 and there were temporary constraints, with triple bagging packaging, crops being inspected and bolters. But in 2012, these were lifted and there are no constraints on its cultivation.

GM technology is also widespread in other crops, with 93% soya, 90% cotton and 90% corn being GM.

Mohamed Khan is professor and extension sugar beet specialist at North Dakota State University and University Of Minnesota.