Wheat growth stage ID tricky but vital says Ben Freer

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Accurately identifying wheat growth stages can be tricky to get right, but crucial for ensuring successful disease protection according to BASF’s Ben Freer.
To help growers “get their eye in” in time for their main fungicide sprays, Mr Freer has produced a short growth stage guidance video.

In the six minute film he explains that “getting the early spray timings spot on will set you well up for the rest of the season.”

“If you see Septoria infections on the tip of leaf three at GS 39, then you didn’t get the spray timings quite right. Either you have either gone too early with your T0 spray, or too late with your T1 spray leaving too long a gap between the applications. If your leaf three is clean, you’ve got your timings bang on.”

His ‘how to’ advice for accurate growth stage identification is to select the main tiller, slice through the stem to see where the nodes are and what stage each leaf emergence has reached. His practical rules of thumb are as follows:

• Less than 1cm from base node to first node = GS 30, the leaf emerging is leaf four and rolled in the leaf sheath; this is too early for T0 sprays.
• More than 1cm from base node to first node, the gap from first node to second node is less than 2cm, and leaf four is well or fully emerged = GS 31, the time to apply T0 spray.
• The gap from first to second node is now 2cm or more, leaf three fully emerged = GS32, the time to apply a T1 spray. Treat any crops that haven’t had a T0.
• Flag leaf (leaf one) fully emerged = GS39, time to apply the T2 spray.

His recommendations for T1 is 1.0-1.25l/ha of Tracker + 1.0l/ha chlorothalonil and at T2, 1.0-1.25l/ha of Adexar + 1.0l/ha chlorothalonil.
“It’s easier to slice the stem with a knife and measure the distance than try to unpick the leaves as you can inadvertently miss the tiny flag leaf at GS 31-32 which can make you think its final leaf three emerging when in fact its final leaf 4. Only in exceptional circumstances is it not final leaf three emerged at GS 32 – unlikely in mid-September to mid-October sown crops.”

“Tracker is a good, cost-effective all-rounder at T1 giving you good Septoria control, plus the boscalid in Tracker will give you very good protection against eyespot and epoxiconazole will deliver very good yellow rust control,” he says.

For T1 sprays, BASF’s Agronomy Manager, Jared Bonner adds some reminders about eyespot: “The disease can cause around 1t/ha yield loss. The main driver for infection is the inoculum from previous crop, so second wheats or wheat in very short rotations are most at risk.

“Early drilling is also a factor but the influence is relatively small, whilst a mild wet spring is also an influencing factor, as the lower leaves cling around the stem making infection more likely to penetrate.

“Minimum tillage slightly reduces the risk so ploughed crops have an inherent higher risk. Soil type is a factor too, with heavy soils that retain moisture increasing the humidity at the stem base creating more risk. Your previous experience of the disease is also very important – if you see it regularly then you should be concerned about it this year.”

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