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Stackyard News Aug 05

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    Take-all Damages HGCA Recommended List Second Cereal Trial Sites

Take-all reached damaging levels at nine out of the 10 HGCA Recommended List second cereal trial sites this season, according to the first-ever monitoring of the disease in these trials. What is more, the only site to show less than moderate levels of the disease wasn't sown until mid-November.

Root assessments taken from dedicated plots at three stages over the season by NIAB at the10 trial sites, from Dorset in the south and west to Perth & Kinross in the north and east, reveal a steady build-up of disease levels in second wheats.

From a level of just under 10 at GS31, the average Take-All Index reached a moderate to high incidence of over 37 by GS65, with high to very high levels recorded at four sites and severe infections at one (Figure).

"Overall, the disease development was in line with what we've come to expect following several years of take-all assessment in second wheat trials," explains NIAB plant pathologist, Bruce Napier. "Infections established early-on only get worse. But the extent to which they develop to damaging levels fundamentally depends on the weather.

"What this study has allowed us to do is track the way the disease build-up across a range of locations and soil types in the same season. And this has been particularly revealing. "It has, for instance, highlighted that take-all can be a serious risk just about anywhere - on heavy soils as much as on light land, in northern Scotland as much as in East Anglia, from later sowings as much as earlier ones, and in wheat after spring barley as much as in true second wheats.

"Indeed, the second highest index we recorded was after spring barley at the Dumfries and Galloway site. And the highest, in Norfolk, was on a medium soil type and from an October 21 sowing.

"Our study has also underlined the unpredictable nature of disease development over the season," he adds.

"The site with the lowest take-all level at GS31 did show the lowest level at GS65 and the site with the highest level at GS31 the highest at GS65. Despite lower than average infection levels early on, however, the Lincolnshire and Perth sites recorded some of the highest eventual indexes. Equally, the sites in Suffolk and Bedfordshire with higher than average early season indexes proved to have some of the lowest levels at the end of the day."

While this was almost certainly due to wetter, more favourable mid-season disease development conditions at the more northerly sites and drier, less favourable conditions in the south and east, Bruce Napier cautions that the pattern of infection may well not be reflected in eventual yield levels.

"Take-all levels were lower in the south, but at over 20 they still classified as moderate to high," he notes. "And with the continued drought they could easily result in higher yield losses from the disease than the more northerly crops with better access to critical soil moisture despite their more damaged root systems.

"It will be interesting to see how individual varieties and the sites as a whole perform in yield terms both relative to one another and to the first wheat trials. But our work certainly confirms that, wherever they are, second wheat growers ignore the take-all threat at their peril.

"Especially so since the crops we monitored were all on well-managed farms and drilled rather later (all but one in October and six after October 10) than many growers may be looking to."

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