As the UK's sugar beet crops reach full establishment, Hutchinsons agronomist, Darryl Shailes, takes growers through the ever-changing agronomic landscape, including a look at ALS herbicide tolerance technology.
Sugar beet agronomy is facing changes and new challenges this year and forward into the foreseeable future.
The immediate issue facing growers is virus risk management without neonicotinoid seed dressings. By May, hopefully much of the crop will be at the 10-12 leaf stage when adult plant tolerance kicks in and gives the sugar beet plant its own defence mechanism against the virus complex. Myzus persicae doesn't like to feed at this later stage and the abdomen goes black as a consequence, as I was told years ago. The mechanism is still not fully understood but is vitally important in this post-neonicotinoid era.
Insecticide applications may still be needed in some situations, and one green wingless aphid per four plants in an 8-10 leaf crop is still a very small target to find, so we will have to be very vigilant in our scouting. Healthy, green crops are less attractive to aphids than yellow ones, so nutrition may also have a role to play in reducing risk.
Weed control should be all but finished as you read this, apart from a few volunteer potatoes which are still emerging, so disease management becomes the next thing on the list.
Effective disease control in sugar beet is one of the things that has helped the beet crop capture some of the yield increase brought about by advances in beet genetics.
If we remember the crop 20 years ago, 50 t/ha was regarded as a good crop but now yields of 100 t/ha are not uncommon. This increase in yield is largely due to variety improvements and managed disease control.
Powdery mildew was always the biggest issue and sulphur was the only product available for many years. Rust has now become more of an issue and needs controlling, along with mildew to maximise photosynthesis.
The modern broad-spectrum fungicides all contain a strobilurin and triazole and do a very good job on controlling both rust and mildew, and the yield benefits from applications are demonstrated every year in BBRO trials.
All crops should receive at least one broad-spectrum fungicide as, even in the absence of disease, there is a yield lift of around 5%. "The rest of the programme should be based around disease pressure, variety and anticipated lifting dates. Three or even four fungicides should be considered in crops scheduled for lifting after Christmas.
Another disease we need to consider now is cercospora, which is the most damaging disease of sugar beet in parts of Europe and the US. One of the biggest issues with this yield-destroying disease is its resistance to the QOI group of fungicides, which is the strobilurin element of our broad-spectrum products and also it's tolerance to the DMI's, which is the triazole component. Where cercospora is an issue, more frequent applications of broad-spectrum contact fungicides such as mancozeb and copper oxychloride are needed where approvals allow. The disease needs hot and humid weather with periods of leaf wetness, so 2018 would have been a high-risk year due to temperature but, fortunately, the disease didn't show in the UK until quite late due to a lack of rain, but it is one to watch out for.
For next season we will have an exciting new development in sugar beet to consider: Convis®Smart from Bayer and Kws. This is ALS herbicide tolerance in sugar beet and will help to simplify weed management in the crop. The obvious place will be those weedy beet fields that will be able to come back into production, but also where weed control is a real struggle or ease of management is a key driver. Volunteer potatoes appear to be well controlled by the Conviso chemistry in the trials we've seen, so this could also be an early target for the technology. Conviso ®Smart comes at a time when herbicides such as chloridazon and desmedipham are going or likely to go.
The stewardship of this new product will the biggest aspect to consider, and ensuring that we keep the technology where its meant to be will be one of the biggest challenges. Bolting and seed shedding are obvious, but also managing re-growth from crowns and grassweed resistance will need to be considered.
We will be looking at this in more detail in our own trials in 2019.
Cover crops bring undoubted benefits in sugar beet rotations. There is a huge interest in them, but are the various different species combinations always considered properly? Beet Cyst Nematode (BCN) is a potential negative of cover crops if the wrong species are grown in front of a beet crop or in a beet rotation. We see a lot of BCN in oilseed rape crops and it wasn't that long ago that it was advised that rape and beet shouldn't be grown in the same rotation. So, what's the effect of a mustard or radish cover crop on BCN? All questions that need to be answered with more work to do and plans to be made.