Greater persistency than its triazole fungicide rivals is what sets BASF’s Tracker apart at flag leaf, according to Irish trials.
“There was around an extra week’s persistency [against septoria] last season,” says Tom McCabe, a researcher at University College, Dublin.
Tracker’s package of septoria, rust and, particularly, eyespot control have positioned it in its first two years of availability firmly as a T1 fungicide in most UK agronomist’s eyes. Its positioning was also set by an initial label restriction preventing applications after GS37 (flag leaf emerging), which was extended to GS51 just before last season.
Dr McCabe was first alerted to the possibilities of flag-leaf sprays after applications in rate response trials were delayed until GS39 by slow disease development in 2004. “It was the first time I got excited by the product because of its duration of control compared with Opus.” Assessments six weeks after application showed a strong residual effect, he says. “We were seeing good leaf retention.”
Trials in 2006, where flag-leaf sprays generally needed some curative activity following two weeks of wet weather before applications, illustrated Tracker’s extra persistence, he says.
For example, on Richmond, where no T1 was applied and products were sprayed with full label rates, Tracker held disease for an extra week into July, while Tracker (1.2 litres/ha) was “a level better” than Opus (0.8 litres/ha) on Einstein sprayed at GS39, he says.
Yield responses in the latter trial were typical of what BASF has seen in other T2 trials – around 0.7t/ha extra from the Tracker treatment, although when both products were mixed with Bravo the response was reduced to 0.2t/ha.
A two-spray trial on the variety Tanker in 2005 suggested similar responses should be possible in more commercial programmes. In the trial Tracker + Bravo yielded 11.1t/ha compared with 10.5t/ha from Opus + Bravo. Proline + Bravo yielded 9.8t/ha.
“Typically at T2 I would expect around 0.5t/ha yield bonus over Opus,” Dr McCabe suggests.
Maintaining high dose rates will be critical to getting responses, Dr McCabe stresses. “At T2 you need a robust rate. Half-rate Tracker won’t give you the kind of response we’ve seen.” Rates should be at least 1.2 litres/ha to give enough epoxiconazole for curative activity, and a good boscalid effect, he advises.
Following his research Dr McCabe now believes Tracker’s best timing is as a mid-season spray, even though it will add to programme costs. “We’ve got chemistry available that can yield better than an Opus programme. It will cost more, but at current wheat prices it will pay.”
Tracker’s extra persistency at flag leaf could be beneficial to feed wheat growers unlikely to apply a T3 fungicide, BASF’s Rosie Bryson believes. “The decision to not apply a T3 is not a simple one, but Tracker could be a good option for those growers who are never going to spray a T3.”
The extra persistence should also help those that do apply a T3, she adds, particularly those using products with strengths other than septoria for other disease targets.