Winter wheat growers are being urged to make sure they apply their T2 flag leaf fungicides on time this season after wet and cold weather disrupted the timing of many earlier sprays.
Iain Hamilton, senior field technical manager with agrochemicals group Syngenta, is concerned diseases may have established on the lower leaves of crops due to the reduced use of T0 fungicides, coupled with worries that some T1 fungicides were applied too late.
“Certainly, fewer crops than normal received T0 fungicides against early disease pressure. Often this was because conditions were simply too wet to spray,” he said.
“When the bad weather did finally break, the sudden spike in temperature in April resulted in rapid crop growth – so leaf three, which the T1 fungicide is designed to protect, emerged unexpectedly quickly. If T1 fungicides went on late, leaf three could have been left exposed to infection for several days,” Mr Hamilton added.
He said septoria is rampant in the west of the country, while the return of higher temperatures will see yellow rust cycle faster in eastern and western regions.
Delayed T1 sprays
If growers were late with T1 sprays, the temptation is to also delay T2 sprays, because the interval between T1 and T2 can seem short. That’s the worst thing growers can do, he warned.
“The optimum is to apply the T2 fungicide as soon as the flag leaf is fully emerged, at GS39.
“Too late, and disease could already be gaining a hold on the unprotected leaf surface.
“Too early, and the base of the leaf won’t have emerged fully, so you’ll be leaving this part of it unsprayed,” he said.
Lincolnshire-based independent agronomist, Ruth East, is also concerned a shortened T1 to T2 interval – caused by crops racing through growth stages to catch up after the late start in her area – might lull growers into being late at T2.
Septoria is the main driver to get spray timings right. However, humidity caused by low cloud and sea frets also makes yellow rust a problem in her area.
“The problem with yellow rust is some varieties have such low resistance you can’t afford to leave it for more than two weeks. Yellow rust pressure has been low, but once it gets going it becomes more difficult to kill,” Ms East added.