Early timing of the T3 ear spray will be critical this season if cereal growers are to maximise the value and efficacy of treatments used, according to Hutchinsons.
Last year’s fusarium ear blight epidemic served as a stark warning of the damage the disease can do if allowed to get established in crops, but also highlighted the value of taking a preventative approach at T3.
Applying the ear spray early, even if there is only a relatively short gap between T2 and T3, proved to be much more effective than waiting, or worse missing the ear spray altogether, says the firm’s James Short in Kent.
“We learnt so much as an industry last year. Early ear sprays are much better than late sprays against fusarium as ‘fire-fighting’ the disease really doesn’t work.
“Fusarium is the number one target for most farmers at T3, but some may look to use it to top up the T2. There is an opportunity to do this, but if you used robust products at T1 and T2 this top-up shouldn’t be needed. With septoria and fusarium prevention is better than cure.”
Ideally the T3 should be applied in a relatively narrow window between ear emergence (GS59) and the onset of flowering, he advises. “That may only be 10-14 days after the flag leaf spray, but it’s still worth going on with the T3 to get the most from it.”
Timing will be complicated this year given the extreme variations in crop development around the country, so it is vital to be ready to go when the time is right, he says. With the majority of T2 sprays being applied during the last week of May, it is likely more forward crops in southern England will be ready for an ear wash spray around Cereals Event week towards the middle of June.
Disease risk
Compared with last year, agronomists say disease risk has been generally lower so far this spring, but crops in many regions are shorter than normal so there may be greater risk of disease spreading onto the ear from lower leaves.
The relatively brief interval between the T2 and T3 sprays should mean that crops will still be getting some protection against septoria and rusts from the SDHIs used at T2, so product choice can be tailored to protecting the ear for as long as possible in the run up to harvest, notes Herefordshire-based Andrew Goodinson.
As a general rule of thumb, in wet, high disease pressure years, such as 2012, the best results are achieved with robust (50-75% of full label dose) rates of prothioconazole-based products, which perform well against both forms of fusarium – microdochium and graminearum, he says.
“Cool and wet conditions tend to favour fusarium microdochium, while when it’s warm and wet you generally see more fusarium graminearum. Depending on the conditions you might get a combination of both.
“Whatever happens though, crops are developing a week or two later than usual and I am worried that the weather hasn’t allowed them to regain lost yield potential, so they will need to stay green for as long as possible to make up lost yield.”
Cropwise agronomist Geoff Mason in Northumberland also favours a prothioconazole/ tebuconazole mix at T3, applied at 75% of full label rate, although a prothioconazole/ strobilurin-type product is also worth considering.
“There will be some difficult choices to make because crop growth stages are so variable. But generally whether you’ve got a good crop or a bad crop, the T3 choice should be the same in theory.”
Mr Short says generally growers should opt for at least 50% of the full label dose rate at T3, but realistically 75% is needed in high disease pressure situations.
Looking to trim costs
While the benefits of a T3 are fairly clear cut for high yield potential crops and milling wheat in particular, many growers may understandably be questioning the value of using a one on thin or patchy crops.
“Thin crops with lower yield potential may not benefit to the same degree from a T3 as thicker, better tillered crops,” acknowledges Mr Short. “And of all the fungicide sprays the T3 is the one that can be questioned in dry, low disease pressure years. But if the weather turns wet and disease pressure increases you can’t turn the clock back, so the T3 really has to be done in anticipation of the weather.”
East Yorkshire-based agronomist Chris Coates also recognises that many farmers may be looking to cut costs after a poor harvest last year and disappointing crop establishment this season. “Last year there was significant fusarium and septoria pressure so many went in all guns blazing at T3 to get control. At the moment disease pressure isn’t as high and there is a feeling that yields will be down, so I’m trying to save for clients where possible while protecting the potential of what’s there.”
Either straight tebuconazole at full rate or a mix of tebuconazole + prothioconazole at a half to three-quarters rate can be a cheaper option at T3 while still giving good efficacy, he suggests. “Even if you’re going for a cheaper option than last year, the key thing is to get the T3 on as soon as ears emerge before flowering. It’s generally only 10 or 14 days after the T2, so growers need to be prepared for quite a quick turnaround.”
Boosting defence
Including a soluble phosphorus product, such as 0.5litres/ha of Phorce, with the T3 may be worth considering, according to Patrick Levinge in Gloucestershire. He says this helped significantly improve fusarium control last season, by as much as 75% in some cases.
Mr Goodinson also found it helped reduce mycotoxin levels last year and also contributed towards improving specific weights. He also suggests including a magnesium trace element which can help grain fill.
T3 advice
· Two types of ear blight to control: fusarium microdochium & fusarium graminearum
· Use triazole (prothioconazole, tebuconazole, metconazole) or strobilurin-based products
· Sprays must go on early as soon as ears emerge & before flowering
· Keep rates up (50-75% of full label dose)
· Consider adding soluble phosphorus product to improve grain fill
