Every day’s delay beyond the optimum T2 (growth stage 39) spray timing costs about 70kg of grain a day in lost yield. So growers must ensure they are ready to go when the time is right, Syngenta’s Matt Pickard says. “Over 60% of yield comes from the flag leaf and leaf two, so any delay could prove costly. Getting held up by a week could lose 0.5t/ha.”
The situation will be even tighter this year due to the 12% higher wheat acreage, adding to already stretched spraying schedules, he says. “For the average 200ha cereal farm this means about one more tank load to spray per day.”
Yet, the weather during mid-May – the key T2 period – can be unpredictable, even in relatively dry parts of the UK, such as Cambridgeshire, he notes. “During the whole of May 2006, for example, there were only four or five days suitable for spraying.”
For that reason, Syngenta’s application specialist Tom Robinson says growers need to ensure they have the capacity to spray all their wheat area in a maximum of three days. “If you know you can’t do that, you should be doing something about it. “Most sprayers these days are 24m units, which, given ideal conditions, should be able to do 200ha a day.”
Brown rust, yellow rust and septoria are the main disease threats at T2, Mr Pickard says. Brown rust grabbed a lot of the headlines last spring, but it is septoria that is the key target this year, he believes. “It’s the disease that’s always there.” Over the past three seasons, Septoria tritici typically affected 70-90% of Syngenta’s trial sites, whereas brown rust was less common 65% of sites were affected last year, but between 2002 and 2006 it affected just 5-15% of sites.
“Some 80% of varieties are rated six or below for rust, but for septoria, Robigus is the only one rated seven, everything else is below that.”
As a result, Mr Pickard advises growers to “cover all bases” with T2 sprays. Adding chlorothalonil (eg, Bravo) to curative triazoles boosts septoria protection over straight triazoles and the benefits far outweigh any risks associated with product antagonism, he says.
Including a strobilurin in the mix fortifies rust activity, he adds. In Syngenta trials at ADAS Terrington last year, adding 0.5 litres/ha Amistar (azoxystrobin) to 0.6 litres/ha Opus (epoxiconazole) + 1 litre/ha Bravo gave a 0.7t/ha or £90/ha yield benefit over the straight triazole + Bravo programme.
“A three-way mix makes a lot of sense, especially, as we don’t know what the weather is going to do,” Mr Pickard says. “Most strobs do a good job against rust and a quarter-dose probably costs around £6-7/ha, but will give you back around 0.2t/ha in yield, which easily covers the cost. Yet, if it rains through May and rust doesn’t come in, by not including chlorothalonil, you run the risk of letting more septoria in.”
Mr Robinson also reminds growers to ensure they set sprayer booms at the correct height to maximise product efficacy and minimise drift. “Ideally, setting booms 0.4m above the crop is best, but in reality this can be tricky, so generally we say aim for 0.5m.”
T2 spraying advice:
- Apply fungicides when flag leaf emerged (growth stage 39)
- Septoria key target
- Adding chlorothalonil boosts septoria control over straight triazole
- Include strobilurin for added rust protection
- Keep sprayer booms 0.4-0.5m above the crop
Syngenta’s new Amistar nozzle (fitted to the left-hand side of this sprayer,
with standard 110 degree fan jets on the right) promises to cut drift at higher forward speeds, Tom Robinson says
New nozzle allows speedier spraying
A new version of Syngenta’s Amistar nozzle will allow growers to spray at faster speeds, without reducing efficacy or increasing drift risk, says the firm’s Tom Robinson. The original Amistar nozzle was developed to work at speeds up to 12kph, but the new 035 version is aimed at those travelling at 14-17kph. It also maintains its fan pattern down to 1 bar pressure. “This is unique among air induction nozzles,” he says. The 13° angle (compared with 10° on the old nozzle) provides uniform deposition on the front and back of targets at the higher speeds, he adds.
The new nozzle has been developed for use with Amistar and Amistar Opti and Mr Pickard says that growers using Syngenta’s azoxystrobin products can get the new nozzles for half-price.