No complacency with wheat rust control
Winter wheat variety choice ahead of drilling this autumn is likely to follow a similar pattern to the current season, with growers relying on the success of many key varieties on farm that have susceptibility to yellow rust.
However, the advice is that whatever the variety choice made, well-timed fungicide treatments in the early spring represent the most cost effective option to providing the foundations of season-long disease control, rather than relying on potentially more expensive seed treatments being applied to seed in the autumn.
Leading agronomist, Andrew Wells says that with winter wheat drilling in mind, in most cases, people will stick with what they’ve grown this year, provided the varieties perform as expected at harvest.
"There’s also the feeling that for the first time in a few years there doesn’t seem to be any outstanding new varieties to opt for to take things forward," comments Mr Wells, who advises growers for the Arable Alliance across land in Nottinghamshire.
Reflecting on the current season, Mr Wells admits that it has been relatively benign in terms of disease pressure in most crops. Being predominantly dry kept the Septoria at bay while the long, cold winter stopped both yellow rust and brown rust getting away.
Also, because of the dry weather, there were a lot of available spray days, he says and most fungicide applications hit their target times during the season. Intervals between fungicide applications were never stretched beyond four weeks, he points out.
"It was an easy season for disease control, but with the varietal split that is going in the ground again this autumn, growers can’t get complacent ahead of next spring," he warns. "It doesn’t mean we can’t grow yellow rust-susceptible varieties like Oakley and Solstice, but there must be some sensible planning and it’s important that manageable areas of these varieties are grown," advises Mr Wells.
He says that the main rust triazoles of cyproconazole and tebuconazole play a key role at the T0 timing and form the foundations for T1, setting the disease control programme up for the season and making it more secure.
"Where people used either cyproconazole or tebuconazole for yellow rust at T0 it worked well this season," he claims. "No, it wasn’t a high disease pressure year, but the treatment wasn’t expensive and was more than likely included in a herbicide or PGR spraying pass anyway.
"Those two are the key rust actives to be used at that time of the season, either alone, or in a mix, depending on the threat facing growers."
Mr Wells continues: "The fear is that in a more typical season weather-wise, when T1 or T2 timings may get delayed, the leaves that contribute most to the final grain yield are emerging and these must be kept disease-free as possible. The benefit of a good rust-active T0 spray is that it gives you a little more flexibility with the timing of the T1 fungicide."
He suggests that growers are better off targeting the rusts at T0 with a reliable rust-acting triazole like tebuconazole, rather than going for a more expensive autumn seed treatment with rust activity.
"It’s asking a lot of a triazole seed treatment to provide protection of a plant 4-5 months after drilling, and, on a cost-per-hectare basis, there’s better value to be had by spraying early in the spring.
"Most people who can get a T0 fungicide on their crop should question whether they need a rust active seed treatment," he adds.
Technical Services manager for agrochemical manufacturer Rotam, James Anderdon, says that tebuconazole remains one of the strongest triazoles for the rusts in the HGCA’s fungicide charts.
"It’s still a leader on rusts and key for early season applications, as well as providing rust control throughout the season in tank mixes and different formulations," he says.
Two of the company’s tebuconazole formulations have received Chemicals Regulation Directorate (CRD)-approval during the past two seasons and are providing growers with cost effective spring fungicide options in addition to standard tebuconazole products.
Odin (250g/l) was launched in the spring this year, while Toledo – the only version of tebuconazole available to UK growers at a 430g/litre concentration – has been on the market since 2009.
"We have good evidence in the UK and across Europe that the products’ efficacy, handling and crop safety are spot on," says Mr Anderdon.
"We’ve also seen good compatibility for tank mixing with a range of other fungicide and insecticide partner products," he adds.
"If farmers are growing large areas of rust-susceptible varieties next season, and have concerns about rust coming into their crops in the spring, then sensible management would suggest that tebuconazole should play an important role in winter wheat disease control strategies in 2011," he says.
