Deciding on T0 fungicides a tricky decision
Regular crop walking is essential to decide whether to apply a T0 treatment, says Oxfordshire independent crop consultant Andrew Cotton.
For wheat he tends to use a T0 where crops were early drilled or are forward with notable disease, especially brown or yellow rust.
On larger farms such treatment is often needed to provide T1 timing flexibility, and the fact that such crops also often need PGR then makes a T0 an obvious choice, he says.
“This year, however, there are few forward crops. Many are showing signs of stress from the winter where sowings were late or slugs severe, and there’s a distinct lack of tillers, so fewer T0s will be used.”
Where needed for brown or yellow rust plus septoria, he plans Cherokee alone – or possibly epoxiconazole with Bravo.
“For septoria only, Bravo at1litre/ha is cheap insurance.”
Where Atlantis is intended, adding chlorothalonil may compromise grassweed control, he warns.
“There are an awful lot of wheat crops requiring Atlantis, but hopefully most will be treated well before T0.
“Normally I don’t apply a T0 to winter barley, and there are very few forward crops this year. But as with every year I’m sure there will be new challenges.”
In recent years most of the wheat Farmers Weekly’s Arable Adviser of the Year Bryce Rham oversees from his Shropshire base has had a T0 fungicide.
“For two years I’ve been applying Mirage plus Bravo which has been very successful.”
There are two reasons, he explains.
The first is where crops reach GS30 in early to mid March with plenty of disease, particularly septoria and eyespot.
“The other question is just how much can you get in the tank at T1? Doing a T0 not only gives you breathing space on the T1, it allows you to sort out other issues – such as growth regulator, cleavers, groundsel or wild oats.”
However, like Mr Cotton he suspects plenty of crops will not get a T0 this time. “Many are late drilled, and with the late drilling and cold winter they’re not very forward, let alone tillered, so there won’t necessarily be the need.
“Also many haven’t had autumn herbicide and will get either Othello or Atlantis, probably mixed with something for cleavers, groundsel, etc. This will reduce need for early broadleaved herbicides and again, in theory, leave just growth regulator and fungicide at T1.
“I’m expecting the Othello and particularly Atlantis to remove Italian ryegrass and wild oats – again reducing the need for a T0.
“I guess about 40% of my wheat is forward enough to require a T0 plus growth reg and herbicide, and I’ll stick to my Mirage plus Bravo.”
Despite this year’s diverse wheat crops, most should benefit from T0 fungicide, maintains ProCam’s Dave Ellerton.
Over several different seasons such treatment has boosted yields by an average of 0.54t/ha (4.3cwt/acre) and given a good economic response, the firm’s 4cast agronomy database shows.
“The key benefits of a T0 fungicide in wheat are not only to cure any disease present and protect against later infections, but to give some leeway with the main T1 fungicide timing.
“If no T0 is applied the T1 timing becomes more critical. Should the weather delay application, diseases such as Septoria tritici may become well established and difficult to control.
“The base product is likely to be chlorothalonil for septoria protection, but triazoles such as tebuconazole or cyproconazole can be of benefit in terms of rust control.”
Adding prochloraz may be worthwhile for controlling eyespot and in creating an anti-resistance strategy against septoria mutations, adds Dr Ellerton.
“T0 fungicides could easily go in with a split dose growth regulator which I think will be particularly useful this year in backward crops.
“I believe T0 treatments will be just as valid this year as last. Although there’s less in the way of established rust at present, there’s a large percentage of rust-prone varieties in the ground this year.”
Like Mr Cotton he warns that chlorothalonil may jeopardise grassweed control if mixed with products such as Atlantis. “So it should be kept separate if possible.”
In barley recent HGCA work highlights the benefits of early disease control in building yield potential through increasing tillers, ears and grain sites, notes Dr Ellerton.
“There seems quite a consistent response and it’s something our Scottish agronomists have been doing for a number of years.
“As with wheat, chlorothalonil with or without a triazole, is the best course of action, the choice of triazole depending on the disease present.”
T0 CASE FOR BAROMETER FARMS IS HARDER TO MAKE THIS SEASON
Whether a T0 fungicide will justify itself this season is difficult to call, says Peter Snell, Dorset, who recently passed his Basis advanced cereal module.
“Fungicide prices look set to rise by up to 30% putting increased pressure on already tightening margins,” he says.
“We haven’t grown winter barley for a couple of years, and when we did we didn’t use a T0.
“However, certainly for the past three years, we have used a T0 on wheat – even the more disease-resistant varieties.
“Last year we used Cherokee at 0.75-1litre/ha as it was well priced. However the T0 yield benefit in trials was very small, and generally we apply such sprays as much as insurance against a delayed T1.
“In 2007 we used a litre of Bravo rather than Cherokee.
“For septoria control my choice is chlorothalonil. If rusts are also of concern I include a triazole element, for example Cherokee or tebuconazole.
“If mildew was an issue – generally it looks worse than it is – Talius or Flexity could be added.
“This year I think our earlier sown first wheat is likely to receive chlorothalonil tank-mixed with a PGR.
“The decision is still to be finalised, but the yield potential is there so why risk problems at this early stage?
“I think our more backward, lower yield potential second wheats are more likely not to get a T0. That gives us the option to save some money and spend a bit more at T1 if required.”
Andy Barr in Kent is no great wheat T0 fungicide enthusiast.
“T0s have always irked me slightly as they only pay for themselves if the T1 is delayed,” he says. “As TAG says, they’re an insurance.
“I’d like to get way from the attitude of bunging chemicals in just because they are relatively cheap and we’re going through anyway for possible growth regulation.
“I have used a litre of Bravo or 0.75 of Cherokee plus some Talius for mildew. But at the moment I can see no disease so this would be a perfect opportunity to leave out the fungicide and perhaps keep the plants healthy with the foliar nutrients I’ve planned anyway.
“But will I or won’t I? At the moment I am veering towards some Cherokee on the Cordiale and leaving the rest.”
Tony Reynolds, Lincolnshire, is unlikely to use a T0 fungicide.
“We’ve been very infrequent sprayers of T0 applications,” he says. “The only times have been when we’ve had to apply a growth regulator early and where this coincides with early indications of disease pressure.
“The snow cover melted only recently and this plus the preceding frosts has left our wheat crops very clean and if not backward certainly not in need of growth regulator.
“So we expect our first spray to be a true T1 at GS32.”
In north Lincolnshire, however, Chris Moore considers a T0 fungicide a must. “When Alchemy broke down with brown rust two seasons ago it taught us a lesson. We now always spray if possible.”
Half this year’s wheat, albeit only two-thirds of that planned, is still Alchemy, he notes.
“We only need 1-2in of rain on our land and we may not get on again for three weeks. So when we can travel we tend to apply the best products.”
Bravo at 1litre/ha is the base to which he’ll add a triazole. “I’m swaying towards Proline.”
T0 treatments for Ian Bird in Durham are rare.
“In the past five years we’ve only managed T0 on about 50 acres a year,” he says. “So I don’t think we will be adding one this year.”
“Our wheat and barley look the worst for 25 years.
“Hardly any crops got rolled and we’ve applied no herbicides. Most would benefit from rolling and the wheats need a PGR and early nitrogen to encourage tillering.
“But the ground is so wet we can’t travel, and I’ve a feeling they’ll jump to GS31 before we know it.”
In Northern Ireland any thought of wheat fungicide spraying is a long way off for James Wray. Still lifting potatoes he only drilled his first wheat, 34ha (85 acres) of Zebedee, on 18 February.
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