Rhizo rising- but it’s not all bad news

RHIZOMANIA HAS been confirmed on 153 new sites this season, more than four times the number seen last year.

But the jump largely stems from ideal conditions for the disease and its identification, and the good news is that the virulent p-type has not been found and the cost of tolerant varieties is falling.

Of the 196 suspect fields identified by aerial observation, 78% proved positive, nearly twice the accuracy seen last year, explains John Prince of British Sugar. Expert spotters and wet conditions in August causing textbook rhizomania symptoms explain the increase.

Late drilling, higher-than-average spring temperatures and high rainfall all favour the disease, he notes. “It was possible to see the longer petioles standing above the rest of the crop even when driving past infected fields.”

But despite the extra cases the total area infected is still less than 1% of the total arable area within the sugar beet rotation.

That compares very favourably with 80% infection in the Netherlands, 60% in France, and 40% in Belgium and Germany, Mr Prince notes.

Further good news is that the price premium for the tolerant varieties recommended for use on farms where rhizomania is identified has been cut from 2004’s 7.50 per 100,000 seed unit to 3 for 2005, he adds.