Beet Cyst Nematode Varieties Provide a Yield Hike

Close attention to detail has seen yields at the Norfolk farm reach 66-69t/ha, knocking on the door of 70t/ha; a highly credible performance on the light, drought prone land.

However, grown in tight rotation – normally at one in every three years – and in a hotspot region for the pest, the farm is starting to see increasing beet cyst nematode damage curtail yields on at risk fields.

“We first saw the problem on one field – part of the reclaimed RAF Watton airfield – that we cleared   in the 80s, returning it to agriculture,” says Malcolm Newby.  “Despite installing a drainage system it has always suffered from structural problems with compaction to depth that we can’t get a subsoiler deep enough into to break it up.”

In the past we put the low yields down to these compaction issues until aerial surveys picked out distinct patches where the crop was yellowing.  “At this stage we thought this was Rhizomania,” he recalls.

“Then, in 2000, we changed our minds.  On close inspection in the spring it was very easy to see cysts on the growing roots confirming that beet cyst nematode damage was the problem.  “While it was recommended that we took the field out of production, this is difficult in the tight rotation that we run.”

So, while the Newby’s didn’t crop the field with beet again until 2006, managing to juggle the beet on rented and other ground, when they did re-crop the field it only did 40t/ha.  “It was a disaster; the beet cyst nematode aggravated by a hot, dry year had a major impact, showing up worse than ever,” recalls Malcolm.

It was at this stage that Mr Newby took the challenge to the beet breeders with the result that he has been one of the first to trial new BCN resistant varieties that just happened to be in the pipeline. 

Last year, he grew the BCN resistant variety Fiorenza in four row beds alongside the rhizo-resistor Opta and as part of trails he also had one trial box of Annouschka KWS, also in the same field, which was closely monitored by the breeder KWS UK and Brooms Barn.

Weighing off every load from the trial area, where infestation was greatest, Mr Newby recorded a 40% increase in adjusted yields from the Fiorenza, compared to Opta.

While this is quite an extraordinary response, that for the Annouschka KWS was even higher.  At 65.6 adjusted t/ha, this BCN resistant variety was 22t/ha ahead of Opta – a 51% advantage.

In comparison Brooms Barn test digs which were hand dug in wetter conditions, earlier in the season gave 18 and 12% yield increases for the two KWS varieties – with the Annouschka KWS again the top performer. 

While the differences may seem strange at first sight, Mr Newby reckons that the magnitude of the response could be explained by the fact that even the small malformed roots were picked up by hand digs, whereas the commercial harvester left a fair amount of these behind.

To put this into perspective, in a section of the field where beet had not been cropped for nine years, and where BCN damage was less evident, the Opta was 6% ahead of Fiorenza, mirroring the type of performance found in NIAB trials on uninfected land. 

Total yields for Opta, on ground that has not had beet for 9 years were very high - in the low-mid 70t/ha bracket – reflecting the very good season.  However Annouschka KWS provided 65t/ha of adjusted yield on ground that had had been cropped with beet every third year.

So, what does Mr Newby make of the performance?  In his view it is important to ensure that you test soils to ensure you do have a problem and match variety selection accordingly.

We’ve now had all fields tested and they vary between 350-1000 eggs per gram of soil.  The problem is that the thresholds vary according to season.   In a bad season like last with a dry June and a dry August, 500 eggs/g may show-up and cause significant damage.  However, we are told that whatever the season,  at 800-1000/g there is certainly an economic return.

On the plus side, the nematode resistant varieties are more drought resistant and are less prone to wilting.  The only downside to Fiorenza and also Annouschka KWS is that they have a very erect growth habit – probably linked to their more drought tolerant nature - and so don’t offer much weed suppression.  As a result we’ve needed to use another herbicide, so you have to add this to the higher seed cost for the BCN resistant varieties.

Mr Newby estimates that this additional herbicide plus the extra seed costs for the more expensive BCN resistant varietiy adds around £50-60/ha to his growing costs.  This though is more than covered for the additional yields seen in last year’s trials.

At the bottom end of those yield increases seen in 2009, a 10% yield response from either Fiorenza or Annouschka KWS is worth an extra £200ha.  This rises to over a £650/ha difference based on the 51% yield response that was recorded by the commercial lift.

“Where we do have an issue I will be growing Annouschka KWS this year and will carry on trialling to check for issues on other less infested ground,” he says.  While he has looked into other cultural or rotational means of cutting the damage, these are hit and miss. 

He does though ensure equipment is washed down after leaving the most heavily infected fields, so as to prevent spread elsewhere around the farm and will continue to ensure widespread use of muck to maximise natural soil potential and structural stability.