DAVID RICHARDSON
DAVID RICHARDSON
Is rhizomania East
Anglias version of foot-
and-mouth? It may be
on the rise but its
certainly not as
serious as that
SEVENTEEN years ago the first UK case of rhizomania, or root madness, in sugar beet was discovered between Thetford in Norfolk and Bury St Edmunds in Suffolk. This autumn, following aerial surveys during the summer and subsequent site testing, 57 cases have been confirmed, all but two of them in Norfolk and Suffolk. The two counties normally account for between 45% and 50% of the entire UK sugar beet crop.
Our own farm has so far escaped. But this year there are half a dozen cases within a five-mile radius, some of them harvested by the same contractor who lifts our crop. Its getting too close for comfort and it is now almost certainly a case of not if, but when, we get it.
Like foot-and-mouth disease it came in from abroad. Not on illegal imports, but almost certainly on seed potatoes imported from Holland. For rhizomania is carried on soil and few grammes can contaminate a field. And although the disease may take years to reach the stage of showing visible symptoms, once discovered the field is banned from growing beet.
The containment policy of which this is a part, almost uniquely adopted in this country, is the botanical version of bio-security, but might also be called shutting the stable door after the horse has bolted. Because you can be pretty sure the virus will have been spread by machines across the field in question and on to others through soil clinging to them.
Even so, the measures adopted by the ministrys Plant Health Division and endorsed by British Sugar and the NFU, have significantly slowed the spread of the disease. Last year only eight cases were confirmed in this country after many more the previous year. But this years wet, late, spring followed by high temperatures in July, led to the rash of cases confirmed this autumn. Water and heat are the two factors the disease likes best and which ensure its rapid spread. If this is global warming beet growers are in for a rough time.
Rhizomania first reared its ugly head – or should I say ugly root, for it looks like a Rastafarians hairstyle when fully established – in Italy. By the time it reached Britain, having travelled up through Europe via France, Germany, Belgium and Holland, the disease was endemic in Italy. So, about 17 years ago I went to Italy to see what it looked like.
It clearly had potentially serious effects on both yield and sugar content, but the Italians shrugged their shoulders and carried on growing sugar beet, as before. The foci of infection grew only slowly, they told me, and with their good land, high temperatures and flood irrigation they could still produce economic crops. Meanwhile plant breeders were busy developing tolerant varieties.
In subsequent years I went to the Beauce region of France, just south of Paris, and to Holland to check further on the spread of rhizomania. In both places a laissez-faire attitude had been adopted and crop rotations had not been changed. The rhizomania-tolerant varieties farmers were growing at the time were yielding significantly less than conventional ones. This relaxed approach has continued across most of Europe, and, indeed America where rhizomania is now a growing problem. Moreover, it is estimated that countries like Holland and Belgium, where they have a tight rotation with sugar beet grown every second or third year, around 90% of the arable land is now infected. The disease stays in the land for many years.
It is worth noting, however, that in all of those European regions that I visited the soil quality and the weather have always enabled sugar beet growers to produce higher-yielding, and, therefore, more profitable crops than we can normally achieve in Britain.
Given Britains relative disadvantages, therefore, I agreed with UK attempts to stop the disease spreading. The original measures included spraying off entire infected fields with glyphosate, putting the land down to grass and taking them out of the arable rotation. This has since been modified to spraying off infected spots and banning the growing of sugar beet on the field.
In other words the regulators have bowed to the inevitable and modified their attitude as the disease spread. It is estimated that some 2% of the land that grows sugar beet in this country is now infected. Which compares favourably with the situation in other countries and has given plant breeders more time to perfect rhizomania-tolerant varieties that are now comparable with non-tolerant ones.
It is not just hope which leads me to suspect the plant health regulators will soon modify their approach again in the light of this years experience. For although British beet growers have cleaner land than most others around the world, it is now clear that rhizomania is endemic in this country. Furthermore, now that around 70% of sugar beet is harvested by contractors there is no practical way the spread can be contained much longer.
Some commentators have said rhizomania is East Anglias version of foot-and-mouth disease. But in truth, with the help of plant breeders and some flexibility by the plant health authorities, it need not be that serious.