Arable News

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Applying the latest variety intelligence to wheat agronomy

Wheat growers across the country should match their management more carefully than ever to the genetics they have in the ground this season for the greatest benefit at the least cost and risk using the latest national and regional variety intelligence.

This is the view of Agrii head of agronomy, Colin Lloyd who stresses that to do so they need to look well beyond Recommended List disease and lodging resistance ratings; especially so with ‘frothy’ crops coming out of one of the mildest winters on record increasing both disease development and lodging risks.

“Later drilling to manage black-grass certainly helped to keep many wheat crops nice and clean coming out of the winter,” he noted. “But early fertiliser uptake in the spring-like February means even these came into April noticeably well-grown and lush.  So the most appropriate disease and PGR management will be essential if we are to make the most of their great potential.

“Despite the lowest disease pressure in recent years, our 13 site national and regional trials  programme with more than 30 varieties recorded a highly cost-effective average response of 1.7 t/ha to our four spray fungicide programme in 2018. 

“Interestingly, though, individual variety responses ranged from 0.5t/ha to 2.14t/ha nationally and from zero to 5.9t/ha in the north. This underlines how important it is to manage varieties for their particular strengths and weaknesses to get the best out of them at the least cost and risk.”

While the Recommended List gives reasonable guidance here, Colin Lloyd is adamant that it needs to be complemented by the most up-to-date intelligence from trial work under regimes that are more typical of commercial agronomy on the one hand and designed to challenge varieties on the other.

That’s why he and his research colleagues produce the regularly updated Agrii Wheat Advisory List bringing their own variety findings and analyses together with RL data to create the best-informed source of variety management information available.

The latest 2019 issue of this guide shows nearly 90% of the 30 main varieties with Agrii trial resistance scores one or more points lower than the RL for at least one of the three main diseases. At the same time, over 40% have untreated lodging scores one full point or more below their RL score (Figure).

Figure: Key Agrii Wheat Advisory List Differences

“These differences primarily arise from the fact that our disease ratings are based on the previous season’s scoring rather than multi-year averages,” Colin Lloyd pointed out. “So if a  variety has broken down to disease in the past season our figures really highlight this.

“Working with ex-NIAB disease authority, Dr Rosemary Bayles, we also take an informed view rather than a simple site average. For instance, in 2015 we marked JB Diego down because it unexpectedly took a lot of yellow rust at just one of our sites. And thank heavens we did because it rapid then broke down nationally.  Rogue results may get in the way of a system designed to minimise environmental variation in assessing genetic potential, but we see them as a crucial early warning growers need to be aware of in their crop management.

“We also try our very best to make varieties fall over with high seed and nitrogen rates, full fungicide regimes but no PGRs on very fertile sites in Cambridgeshire and Lincolnshire,” he added. “This certainly sorts out the men from the boys in standing power.

“Yes, it’s a worst case scenario. But it means we know what we’re facing and which varieties shouldn’t be sown too early, on sites with too much fertility or given too much nitrogen or too little growth regulation.

“A relative weakness to a particular disease or in the straw is something we can easily address to get the most out of an otherwise excellent variety. But we need to know about it.”

The Agrii Advisory List has a clear management alert for every one of the seven varieties than make up half of the current season’s wheat plantings. Overall, 43% are markedly more susceptible to yellow rust than their RL scores suggest; 71% have a more obvious brown rust susceptibility and 57% are clearly weaker in the stem.

Stand out examples include Skyfall with a yellow rust resistance score of 3.4 (5.4 on the RL), KWS Kerrin with a brown rust score of 4.2 (against 6.8) and RGT Gravity with a untreated lodging score of 4.0 (6.7).

“These are all good varieties providing we manage them right,” insisted Colin Lloyd. “With Skyfall it’s a matter of keeping up the azole partner at T0 – even though it continues to have reasonable Septoria strength – and being particularly careful with T0 to T1 and T1 to T2 intervals. With KWS Kerrin, it’s vital to use the right SDHI at T2. And RGT Gravity should never be planted too early and needs a robust PGR programme.
“For the future, KWS Extase and KWS Firefly are certainly varieties to watch for those wishing to make the most of genetics in their agronomy. They gave even lower average responses to fungicides than Graham across our trials network last season, have good straw strength and, unusually, are relatively early to mature.

“Declining fungicide options as well as changing varietal resistance make variety-specific agronomy more important than ever,” he concluded. “We can’t completely guard against the sudden emergence of a new yellow rust race in season, of course. But we can substantially reduce the risk this poses with variety mixes selected to avoid the most obvious pedigree pitfalls using the variety diversification regime we also maintain with Dr Bayles.”

Extra Intelligence

As well as the most up-to-date intelligence on disease and lodging resistance and yellow rust diversification, amongst other characters, the 2019 Agrii Wheat Advisory List rates varieties for:

  • Grassweed competitiveness;
  • Yield consistency;
  • Yield resilience under disease pressure;
  • Relative second vs first wheat performance;
  • Soil type suitability; and
  • Sowing date suitability.

  • Written by: Farmers Guide
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