Urgent call for soil testing to tackle beet cyst nematode

• Pest more widespread than thought

• Better field hygiene must be priority

• Action needed to avoid yield losses

Sugar beet growers are advised to ramp up soil testing to combat the increasing threat from beet cyst nematode.

The pest is present in all four factory areas serving the UK sugar beet area – making it more widespread than thought, says British Beet Research Organisation (BBRO) crop protection scientist Alistair Wright.

Historical assumptions are that only 6-10% of land was infested. But Dr Wright thinks it is now more like 25-30% – a concern because the nematode can cause up to 60% yield losses.

Field hygiene

“There’s more out there than growers take for granted and the reason is because field hygiene is generally not good enough,” Dr Wright told the Association of Independent Crop Consultants  conference.

Cysts containing juvenile beet cyst nematodes hatch out and invade roots of host plants to continue the pest’s lifecycle, can persist in the soil for a decade making it hard to eradicate.

It is also spread via wind, water, wildlife and livestock movement, but machines such as harvesters are the number one enemy for moving through large areas with no cleaning.

RiskField hygiene

Another factor increasing beet cyst nematodes risk is warmer spring soisl, caused by climate change, allowing the pest to complete an extra generation or two a season.

Cover crops and SFI options are contributing too by helping the pest proliferate with common constituents like oil radish, tillage radish, white mustard, vetch and buckwheat being nematode hosts.

Good management is required, especially when it comes to the correct sowing date and destruction afterwards. That’s because  these species facilitate significant multiplication in the soil and increase yield loss risks in crops.

Soil sampling

At about £100/sample BCN testing is costly, due to the specialist equipment and rare expertise required by labs to speciate the pest, but Dr Wright believes it is money well spent.

“Get out there with a soil corer and bucket: it could really help you avoid those massive yield losses,” he says.

Testing results will inform effective targeting of tolerant varieties, which help avoid significant multiplication, and are by far the most straightforward management tool.

Furthermore, knowing where populations are located will help growers avoid planting susceptible cover crops that could host the pest and increase numbers ahead of beet crops.

Although biofumigation is used against other cyst nematodes, such as potato cyst nematode, Dr Wright says the brassica species used for PCN biofumigation are hosts to nematodes, so it might not have a role in sugar beet.

Instead, he sees trap crops of resistant radish and mustard varieties as more useful achieving 40-50% reductions when managed well, but results can vary significantly between years.

“Use class 1 varieties if you can, which are the most resistant. Class 2 varieties are OK if you have a low level of fields, or where you don’t think there’s any nematodes but it’s a high-risk soil type,” says Dr Wright.

Norfolk AICC agronomist Penny Oakes explains that soil testing is already a very important management tool – and stresses the importance of tightening up field hygiene too.

This involves cleaning farmer and contractor machinery as it leaves fields, particularly where testing has identified a population and there is a risk of transferring cysts to clean land.

Beet spoil around cleaner/loaders is another area of concern and where possible, it should be returned to the field of origin to isolate any nematode issues.

“Monitoring crops for symptoms is a good habit to get into, with summer the best time to pull up roots and look for the white cysts on roots.

“It’s important to make detailed records of where problems are as well, as alongside soil sampling and testing, it will help accurately guide future management.”

BCN management – key points

• Beet cyst nematode is widespread and has been underestimated across the sugar beet area
• Warmer climate and certain cover crops are exacerbating the problem
• Regular soil testing is essential for detecting beet cyst nematodes  and informing strategies
• Tolerant varieties and trap crops are useful in reducing multiplication
• Good field hygiene and record keeping habits key to long-term control