Great Britain

Leaf Layer Live 1: Care needed with backward plant dissection

In conjunction with Bayer we will be keeping track of winter wheat development over two cultivation strategies, and using Rapid Disease Detection results to monitor disease progress through the season.

As we move towards the critical part of the growing season, we pay our first visit to the variety trial at D J Tebbit Farms.

Farm manager Russell McKenzie and Bayer’s Ben Giles, in conjunction with KWS, are looking at winter wheat development over two cultivation strategies, and using Rapid Disease Detection to monitor disease progress through the season.

Four varieties are being assessed with varying septoria resilience and development profiles. These are Saki (6.5), Cranium (6.0), Skyscraper (5.1) and Kerrin (4.8). All varieties have been established using a direct drilled set-up or via min-till cultivation strategy.

Cultivated crops have more biomass, thought to be down to improved early nitrogen take up.

Cultivated crops have more biomass, thought to be down to improved early nitrogen take up.

Cultivations

The cool start to the season has put the break on crops, but there is a clear difference between the min-till and direct drill plots.

Whilst visible at ground level, drone images highlight those differences more clearly, with the cultivated plots having greater biomass. Ben and Russell believe it might have improved early nitrogen take up.

Disease

At the moment it is good news on the disease front. Despite yellow rust and septoria being visible on the lower leaves, Rapid Disease Detection hasn’t found the disease firmly established on new leaves.

Ben and Russell have been testing weekly to track septoria and yellow rust progress. Using rapid qPCR technology, they receive septoria and yellow rust DNA measurements within 48 hours of tests being undertaken.

Septoria DNA readings peaked during mid-March but cool, breezy conditions have meant it hasn’t infected the newly emerged leaves yet. Yellow rust has also been kept at bay.

But Ben thinks this will change as testing focuses on the key yield-bearing top three leaves.

“It will be interesting to see how the disease develops on leaf 3 over the next few weeks. Yellow rust and Septoria are visible in both Kerrin and Skyscraper, with septoria higher up the canopy in Skyscraper at the moment.”

Skyscraper dissection.

Skyscraper dissection.

Saki dissection.

Saki dissection.

Emergence

All October drilled plots are at GS30 but leaf 3 emergence on the main stem varies slightly. Leaf 3 is around 25% emerged in Skyscraper, but with Saki it is only just emerging (see pics above).

And the small size of plants means identifying which leaf is emerging can be extremely difficult in the field. With flag leaf and leaf 2 just a few millimetres long at the moment, when dissecting plants Ben needed the aid of optics to truly establish which leaf he was looking at. “What might look like leaf 3 could be leaf 4 with leaf 3 still to unfold,” he says.

He doesn’t think there will be great differences in T1 application dates but does think if cool conditions continue then applications could be five to seven days later than the norm.

“That T1 is likely to be Ascra (prothioconazole + bixafen + fluopyram). That’s because the combination of azole with two SDHIs offers strong protection against both yellow rust and septoria. Aviator (prothioconazole + bixafen) is an alternative due to its higher prothioconazole loading.

“Either product could be combined with tebuconazole to give more rapid yellow rust eradication if the disease re-establishes between T0 and T1 timings. Both are highly dose flexible so this can be matched to the variable disease pressure we might see between varieties of different disease ratings,” says Ben.

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