Full-rate fungicide rates required to recoup sugar beet yield and provide consistent disease protection

Sugar beet growers are being advised to focus on their fungicide applications this season to recoup potential yield losses from establishment difficulties experienced earlier in the year, as well as protecting the crop against the likely threat from powdery mildew and other major diseases.

According to Suffolk-based research station, Broom's Barn, fungicide use on sugar beet can increase yields by an average of 5 per cent brought about by the 'greening effect' in the crop. "In a 60t/ha crop, this could equate to a three- fold benefit over the cost of the fungicide application," says UAP advisor, Will Foss. "Provided the final spray is made no later than 4 weeks prior to lifting,"

he adds.

Mr Foss, who advises growers for UAP across combinable and root crops in East Anglia, says that much of the sugar beet crop this season was either drilled very early, resulting in 'gappy', low plant-populated crops, or re-drilled later, with less yield potential. "Growers now have the opportunity to reclaim some of that yield, in addition to protecting the crop against potential disease threats," he comments.

With as much as 75 per cent of beet varieties currently in the ground having a 'sub-5' rating against powdery mildew, Mr Foss warns that the next few weeks will be crucial in determining the extent of the disease this season. "Nothing seems to have appeared in the crop as yet and we will need warm, humid weather before the disease begins to spread in from its traditional starting points on the Suffolk and Essex coasts. But, from now on, growers need to be on alert," he stresses.

"There's also the threat of rust, ramularia and cercospora to consider," adds Mr Foss. "Cercospora, a relatively recent threat to these shores, is very apparent on the continent where, in the Netherlands, numerous sprays are applied each season to control it. There's been no serious reports of it in the UK up until now, but in the past we have seen other diseases establish themselves on the continent before coming over here into our crops," he warns.

With cereal harvest already underway, Mr Foss says that growers will have to make the choice about when to apply fungicides to the beet crop. "If they go early then there'll be good activity initially but it will be less effective later on as the product runs out of steam. However, if growers are planning a two-spray programme then going now is fine, if the intention is to spray again later.

"It's probably best, however, with no signs of disease in the crop at the moment, to hold off and spray a bit later towards the end of July, unless disease appears in the meantime," he advises.

Mr Foss recommends triazole, Genie (flusilazole) for good, early season activity on powdery mildew, while also offering some activity on cercospora and rust.

"If growers are thinking about two applications then an early season treatment of Genie, followed by Escolta (cyproconazole + trifloxystrobin) would be our preferred option. Escolta has been shown to have control of mildew, rust, ramularia and cercospora, and has the added benefit of a 21 day harvest interval providing flexibility with lifting dates," he says. "If spraying once, then Escolta is our product of choice as it covers all four diseases and also delivers leaf greening benefits and yield response, even in the absence of disease."

Data suggests that, whatever fungicide choice growers make this season, they should maintain full rates. "The problem with reduced dose rates is that they affect the consistency of response which is more variable than when full rates are applied. Full rates give you more product persistence too," he adds.