Getting fungicide timings right is essential for effective disease control. Abby Kellett got some tips from a spray application expert as the spraying season approaches.
The reduced efficacy of a range of fungicides means applying the T1 spray at the correct time is more crucial than ever.
T1 should be applied at growth stage 31-32 so it protects leaf three as this contributes to a large proportion of the final crop yield along with leaf two and the flag leaf.
Plus, with fungicide resistance creeping in and given the reduced efficacy of triazoles, there is little you can do in the curative phase, so good timeliness at T1 is all the more important, says Syngenta spray application specialist Ben Magri.
He says: “If you miss your T1 application, then you run the risk of getting disease on the lower leaves of the crop and you will struggle to keep on top of it.”
But while it may be tempting to get a head start when going in with the T1 fungicide, spraying too early can be just as costly as delayed application, he warns.
“If you go too early before leaf three has emerged, although you may think you have done a good job, you have basically left an untreated zone in the plant. When leaf three emerges, there will be an area of unprotected material which disease can be transferred onto.
“If you are too late, leaf three will have emerged and it will have been exposed to the pathogen for longer than it should.”
While predicting when the T1 timing will be is difficult, it pays to know your varieties and the dates all crops were drilled in order to select which ones should be take priority, he says.
“Make sure varieties which are more forward and early drilled crops are treated first.”
Taking into consideration the disease resistance ratings of varieties can also help prioritise crops for fungicide treatments.
He says: “Some varieties will be more at risk, as they are less resistant to rust and septoria which are prevalent this season.
“Others will offer an element of natural resistance, so you can put those further down the list.”
When considering nozzle selection, he suggests opting for air induction nozzles over traditional flat fan ones to help reduce drift and increase the amount of available spray days.
“Make sure you use air induction nozzles. We recommend the Amistar nozzle which we developed especially for cereal fungicide spraying.”
Another benefit associated with using induction nozzles is the ability to spray faster. “There is no need to go really slow but we recommend not going more than 14km/h.
"By sticking to this speed, you should get good coverage all the way down the plant and good protection of leaf four and five as well.
“You will never do a bad job going slow, but 14km/h gets you round and gets you a more timely application without compromising coverage.”
By reducing the overall spray volume to about 100 litres of water per hectare, fewer fill-ups are required, he adds.
“The more water you apply, the more often you will have to fill-up so we recommend using 100 litres/ha as your standard spray volume. Any less and you probably will not get the coverage you require.”
Mr Magri also identifies the use of bowsers as something which has proved a good way of boosting the efficiency of spray programmes.
“While travelling back to the filling site from the field you are not spraying crops, so by pulling a bowser behind the sprayer, or having somebody fetch the bowser to the field, you can often reduce downtime,” he says.
Source: Ben Magri, Syngenta