Take-all levels at HGCA Recommended List second cereal trial sites
have been noticeably lower than last year, but losses from the
disease are expected to be considerably higher in the face of much
increased levels of summer drought stress.
The average Take-All Index built up to 17 by GS75, reveal root
assessments taken from dedicated wheat plots at three stages over
the past season, with only two of the 12 sites across the country
showing Indexes of over 25. This compares with an average Take-All
Index of 37 and eight out of 10 sites at over 25 in 2005.
“Interestingly, this year’s root infection levels were very similar
to last season at GS31,” comments study co-ordinator David Leaper of Monsanto. “But
the very much drier conditions of this summer restricted late season take-all
“While limiting the further development of infections on
the one hand, the drought has undoubtedly made their impact
worse on the other,” he points out. “We know that even
relatively modest levels of take-all can result in serious yield
losses in particularly dry summers. So it’s not surprising
whitehead problems have been developing widely in second wheats
over the past three weeks, although eyespot could be as much to
blame as take-all in many cases.
“With two thirds of the RL trial sites showing moderate levels of take-all
according to the NIAB root assessments, we look like being in for even higher
levels of yield loss than we saw last year despite the lower levels of disease
and the fact that none of this season’s second cereal sites are on the
most vulnerable sandy ground.”
As in 2005, the current year’s trial site monitoring underlines
the great unpredictability of take-all development and the extent
to which it can cause problems almost anywhere under any conditions.
As might be expected, the lowest level of take-all infection was
recorded in the latest sown site (October 22) and the highest level
in the one of the earliest sown (September 30). However, a site
sown on October 19 showed considerable disease levels while one
sown on September 29 showed only low levels; and this despite both
being on deep clay land.
Equally, there was little correlation between region and infection
level, or between early and late infection levels.
For instance, the four most infected sites were in Perth & Kinross,
Londonderry, Warwickshire and Lincolnshire while the four least
infected were in Dorset, Northumberland, Norfolk and Yorkshire. And
the site showing the second highest level of infection at GS31
proved to have one of the lowest levels at GS75, while, of the
three sites with very low GS31 infections, one was still very low
at GS75 and the other two developed moderate infections.
“Both the 2005 and 2006 monitoring shows that take-all can build-up to
potentially damaging summer levels in second wheats wherever they are, whenever
they’re drilled and whatever their initial level of infection,” notes
“This emphasises that second wheat growers simply cannot afford to ignore
the risk the disease poses. Especially not if future summers put wheat crops
under as much drought stress as many have been experiencing this season.”
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