Recommended List Site Take-All Tracking Underlines Disease Risk and Unpredictability
28/07/06

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 development.

“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 David Leaper.

“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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