Fungicides can aid

2 June 2000

Fungicides can aid

key quest to meet

A + B quota targets

FUNGICIDES could prove valuable to ensure A + B sugar beet quota targets are met this season, says Martin Lainsbury of Morley Research Centre.

Trials last season gave up to 12% yield responses from treatments, which on a 60t/ha crop could be worth £180/ha (£66/acre). But if the extra output is all C beet the return becomes marginal at last seasons prices, he warns.

However, many growers have cut crop areas and a less than ideal growing season could leave some struggling for tonnage, especially if diseases go untreated.

"Brooms Barn forecasts that 52% of the national crop will be infected with powdery mildew by the end of August, so damage is likely to be similar to last year," says Mr Lainsbury.

Rust adds to the risk of yield losses in unprotected crops, so growers need to keep a close eye on crops for either disease from late July, he says.

Growers have three treatment choices. "Sulphur is the cheap option but it only does mildew, whereas the triazoles, Punch C and Alto, do both mildew and rust."

Both triazoles increase crop greenness late in the season, and later liftings produce the biggest responses.

Of the two products, Punch C (flusilazole + mbc) is the more persistent, giving about eight weeks protection from a full-rate application of 0.625 litres/ha. Alto (cyproconazole) at 0.25 litres/ha lasts about four weeks.

"But it is more effective against rust, and has a shorter harvest interval – 14 days compared to seven weeks with Punch."

Besides adding rust control, and producing bigger yield responses, the triazoles are easier to mix and spray than sulphur, he continues.

"The recommended sulphur rate is 10kg/ha in a high water volume and it is not particularly convenient."

Reduced rates of sulphur and Punch C have given good results, but there is a danger of cutting doses too low so neither product works and persistence is reduced, he warns.

Treatments should be applied at first sign of either disease, but only if there is a chance of yield falling short of A+B quota, or if the price prospects for C beet are better than last year, he concludes.

Fungicides can help ensure quota is met. But using them to produce C beet is questionable.

Strobs on beet

Early signs are that strobilurin fungicides do not produce the same dramatic yield responses as growers have seen with cereals, says Mr Lainsbury. "From what I have seen so far in trials here, they dont offer anything that we are not already getting from the triazoles." However, manufacturers have not formulated mixes specifically for sugar beet yet, he says.


&#8226 Up to 12% yield responses.

&#8226 Triazoles best for late-lifting.

&#8226 Sulphur cheap, but mildew only.

&#8226 Extra C beet makes treatment marginal.

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