Syngenta Crop Protection UK Ltd
Clean beds cut soil pathogens
24/11/2009
Amistar application and incorporation into potato beds prior to planting could achieve the effective control of soil-borne pathogens to deliver cleaner, brighter skin finish on tubers, along with more consistent tuber size and quality for better processing results. Trials and recent growers’ experience has highlighted overall bed incorporation can be equally effective as effective as in-furrow treatment.
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Amistar incorporation into beds could provide effective control of Rhizoctonia and Black Dot
Syngenta Potato Manager, Tom Whitworth, points out that incorporating into the bed targets treatment on soil pathogens throughout the growing zone. Speaking at British Potato 2009 this week (25 - 26 November) Mr Whitworth announced a series of new field trials planned for the coming season to further evaluate and refine the techniques.
Whilst the Amistar label recommends overall application at six litres per hectare, since bed systems typically covering 80% of the field area, growers have shown they can achieve good results with the pro-rata rate of around 4.5 litres of Amistar targeted into the beds.
“Application can be quickly and accurately achieved with conventional farm sprayers, by blanking out some nozzle outlets to just spray the beds, or with purpose designed spray bars fitted in front of the bed tillers,” reports Mr Whitworth. “Furthermore, the bed incorporation technique simplifies and speeds up operation of the potato planter, compared to in-furrow application. It also minimises any associated risk of concentrated spray coming into direct contact with the seed tuber.”
Nottinghamshire grower Peter Knight has already undertaken two-years of Amistar bed incorporation at Willow Tree Farm, Long Bennington near Newark. “We do put on a seed treatment, so are really looking for the Amistar to have the greatest possible affect on the soil borne pathogens,” reports Mr Knight. “Incorporating in the bed is simple, fast and appears an extremely effective way of achieving it.”
Rhizoctonia stem and stolon pruning (top) can affect crop establishment and consistent tuber initiation, compared to crops growing in Amistar treated soil (below)
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In trials tubers from crops growing in Amistar treated soil (below) have been more consistent in size and have better skin finish
An in-bed Amistar treatment in 2008, on a crop of Melody with a 170 day growing season, saw Black Dot infection effectively halved. Evaluation of the harvested tubers by Cambridge University Farms showed 87% of tubers affected in the untreated beds, but only 48% with the Amistar control. More significantly the severity of the infection was reduced from 11.6% of the tuber surface without treatment, down to less than 5% with Amistar.
Furthermore, Mr Knight highlights the trials have also shown a significant 38% reduction in tuber surface area affected by Silver Scurf. Fields of the premium baking variety Vales Sovereign treated with Amistar were also significantly cleaner and brighter, he added. This season all the farm’s Amistar treatment was applied in the beds.
Tom Whitworth adds that incorporating Amistar throughout the top 15-20cm of the bed profile can give excellent protection against Rhizoctonia stolon pruning as crops grow and develop. “Rhizoctonia control, to prevent stolon pruning and avoid secondary tuber initiation, is especially important to achieve consistent tuber size and quality in processing and packing crops,” he says. “Bed incorporation could prove especially effective results as the roots extend throughout the soil profile.”
In field trials, assessed two months after planting by Cambridge University Farms, Amistar reduced the level of stem and stolon canker on plants growing in Rhizoctonia prone soils from 50% of stems affected on untreated plants, to 10% with Amistar treatment. Conventional pencycuron seed treatment reduced infection by just 8%.
Stem pruning caused by the soil-borne Rhizoctonia pathogen, which affects an estimated 60% of UK potato land in regular cropping, can trigger secondary tuber initiation, leading to inconsistent tuber size and maturity at harvest. The variable dry matter and sugar content in the tubers can adversely affect fry colour and manufacturing quality of processing crops. The delayed emergence and variable crop growth from secondary tuber initiation also complicates management and irrigation scheduling of the growing crop.
Reducing the level of splits, cracks and tuber skin damage associated with Rhizoctonia Black Scurf at harvest also minimises processing waste, which can add hugely to processors costs, adds Mr Whitworth.
Read more about using Amistar to combat potato soil diseases
