Protect crop base after mild conditions, growers urged

Be sure to monitor the state of cereal crop bases and take necessary action to fend off disease and lodging pressure at this month's major T1 spray timing, growers are being urged.

The stem base provides the foundation for the whole plant, says Syngenta technical manager David Ranner, but mild weather has provided ideal conditions for infections of eyespot. Also, thick crops brought on by the mild winter are likely to have weaker stems – leading to increased lodging risks, he points out.

"The T1 spray timing in April is a key opportunity for growers to tackle these issues," explains Mr Ranner. "Therefore it will be important to get out and assess risks.

"Lodging can cut yield by a quarter, and we know it's a high lodging risk season. Having been so mild you'd also expect eyespot infection. Yield gains in trial plots of up to 1 t/ha can make specific eyespot treatment with the fungicide Unix very worthwhile," he points out.

Independent researcher Richard Gutteridge of Rothamsted Research agrees that 2007 could be a high eyespot risk season. This isn't only based on the mild winter, he says, but also the high incidence of eyespot last season providing inoculum for carryover. Recent cold snaps will have also encouraged spore release ready for re-infection, he adds.

"There was a lot of eyespot last year," explains Mr Gutteridge. "That gives the potential for infection this year. We've had cold spells which should give good sporulation.

"If you don't spray and you have a risk you could come unstuck with eyespot. Even first wheats should be checked as these can be just as vulnerable to the disease as second wheats," he adds.

According to Mr Ranner, laboratory testing so far this season has shown the majority of eyespot infections contain the R type of the disease. Not all fields are testing positive, he says, so it makes sense to target eyespot fungicides only to those fields at risk.

Unix has the benefit of giving protection, not only against the W type of eyespot, but is also highly active against the dominant R type as well, Mr Ranner points out. However eyespot is only part of the picture he adds. "Unix has a wide range of tank-mix partners such as Cherokee for foliar diseases, which provides a very cost effective option.

"We also know that many early-drilled wheat crops have high numbers of tillers following the mild winter, and overcrowded crops grow taller and thinner which exacerbates any weakness at the stem base.

"Therefore, for dense crops in particular, a T1 application of the plant growth regulator Moddus at growth stage 31 to 32 may be important to keep crops standing. This timing is crucial because this is the optimum to make the most of the ability of Moddus to increase stem wall thickness and thereby increase stem strength."

As well as stem base issues, Mr Ranner says the root disease take-all should also be monitored after the mild winter, particularly in second or subsequent wheat. Black, rotted roots are a classic symptom of the disease, with potential yield losses of 0.5 to 4 t/ha.

"Take-all infection occurs above 10 degrees C, and it's been above 10 degrees C for sure. The strobilurin Amistar has label approval against the disease. Furthermore, results indicate that a period of rainfall a few days after Amistar application can improve take-all reduction, by washing it down into the root zone," he adds.