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Downgrades prompt call for action

 

Blackleg caused by Pectobacterium atrosepticum is no stranger to Scotland. The cool, wet climate has been the disease’s ally and seed growers have to work hard to keep it at bay, writes Dr Stuart Wale. In the 1960s it was a major problem and threatened to relegate Scotland from being a major seed producer. The answer at that time was to change the way potatoes were produced.

The introduction of the Virus Tested Stem Cutting Scheme and minituber production, along with fewer field generations, reduced the significance of the disease but this wasn’t the only approach: growers took up positive ventilation, shifted away from poorly ventilated ambient stores to modern refrigerated units and  earlier harvesting. The number of stocks with blackleg exceeding tolerance fell below 5% and after 1992 the figure was often a lot less.

There is no doubt, however, that a run of difficult wet and relatively late harvests have not helped but other factors may also have been implicated in the rise of blackleg. One of these, frequently cited, has been the loss of sulphuric acid as a haulm desiccant.

The move to desiccation or pulverisation has meant a major change in approach for many. Pulverisation, in itself was condemned some years ago as a way blackleg could be spread within and between crops. The original work by Dr Michel Perombelon at SCRI (now the James Hutton Institute) led him to criticise flailing but the technique has come a long way and it is unclear whether the relatively closed nature of modern equipment represents the same sort of threat.

A preliminary PCL-funded evaluation comparing pulverisation and desiccation in 2009 suggested that flailing was not a problem for ‘commercial’ seed crops. A follow-up project in 2011 evaluating a range of haulm destruction programmes has yet to report its findings.

 

For the full article see March/April edition

 

 

Fertigation could ease pressure

The English potato crop is largely grown in areas which are under threat from water shortages – climate change is already thought to be making that situation worse, according to Dr Mark Else, of East Malling Research. Conversely, over-wet soils during the period of scab control can affect tuber numbers and quality and encourage leaching of nitrates and other nutrients, causing diffuse pollution.

If growers are to maintain or increase yields against a backdrop of rising summer temperatures, dwindling water supplies, and government demands for greater environmental protection, new production methods improving water and nutrient use efficiency and exploiting best practice are needed.

 

Integration is key to PCN planning

Nematicides play an essential role in protecting potato crops against soil pests and achieving sustainable production, says Syngenta potato technical manager Stephen Williams. ‘Identifying how, where and when to use them in the rotation will ensure minimal risk to the crop, the   environment and operators. Accurate application will help to minimise the damaging effects of PCN, wireworm and free-living nematodes,’ he adds. ‘With the value of the crop at stake it makes sense to ensure that nematicides are being applied as effectively as possible.’

Syngenta’s Georgina Wood, addressing a workshop in February at Worth Farms, Holbeach, Lincolnshire, pointed out that soil sampling gives a useful assessment of PCN risk so they can get the best out of an integrated crop management programme and optimise the targeting of nematicides.

She advised growers always to sample in sufficient time to adjust cropping plans and tailor agronomy if required. Where a soil test detected no eggs (or only non-viable eggs) no treatment would be necessary but they should not be complacent about potential soil pests and should maintain as long an interval as possible between potatoes in the rotation.

‘If low levels of egg counts are detected (one to eight eggs per gram of soil), we would strongly advocate that growers treat the soil at planting to minimise the risk of crop damage and the build-up of nematodes,’ said Miss Wood. ‘That’s especially important if crops are close in the rotation, or on light soils where there is additional stress on the plants.’ Growing a PCN resistant variety may also help to limit nematode multiplication, she remarked.

With moderate egg counts (8–15 eggs/g) treatment is highly recommended and growers were urged to consider using a nematicide in combination with a resistant variety. Where high levels of infestation are detected (>15 eggs/g), she advocated considering the use of alternative fields, although levels of up to 30 eggs/g may be acceptable on silts and high organic matter black land.

‘Regular sampling before cropping will help growers track changes in populations and adopt a proactive strategy to prevent build-up to damaging levels. With appropriate management and good stewardship alongside the use of nematicides, the problem of soil pests can be effectively managed,’ she added.

 

For the full article see March/April edition

Most irrigation is scheduled either using water balance models that calculate potential evapotranspiration or by reference to the soil moisture deficit (SMD). These methods have been used for many years and are generally quite good at predicting irrigation need but recent work at EMR suggests scope for improving on current tools by combining monitoring of plant–water relations with more sensitive techniques for measuring soil moisture availability at critical positions in the rooting zone.

Key stages during plant physiological processes such as leaf growth and photosynthesis have been identified and used to calculate irrigation upper and lower set points between which yields and quality are optimised. Such information enables drip irrigation strategies to be developed for the range of different soil types in which potatoes are grown.

This approach has been developed at EMR for drip irrigated, field-grown strawberrys; in commercial trials, water savings of 36%, fertiliser savings of 21% and improved class 1 yields of 18% have been achieved, in addition to quality improvements. There is scope for transfer of the technology into the potato sector, albeit that most potato irrigation still relies on overhead application – new guidelines would be required to cater for both overhead and drip systems.

 

For the full article see March/April edition

 

Integration is key to PCN planning

Nematicides play an essential role in protecting potato crops against soil pests and achieving sustainable production, says Syngenta potato technical manager Stephen Williams. ‘Identifying how, where and when to use them in the rotation will ensure minimal risk to the crop, the   environment and operators. Accurate application will help to minimise the damaging effects of PCN, wireworm and free-living nematodes,’ he adds. ‘With the value of the crop at stake it makes sense to ensure that nematicides are being applied as effectively as possible.’

Syngenta’s Georgina Wood, addressing a workshop in February at Worth Farms, Holbeach, Lincolnshire, pointed out that soil sampling gives a useful assessment of PCN risk so they can get the best out of an integrated crop management programme and optimise the targeting of nematicides.

She advised growers always to sample in sufficient time to adjust cropping plans and tailor agronomy if required. Where a soil test detected no eggs (or only non-viable eggs) no treatment would be necessary but they should not be complacent about potential soil pests and should maintain as long an interval as possible between potatoes in the rotation.

‘If low levels of egg counts are detected (one to eight eggs per gram of soil), we would strongly advocate that growers treat the soil at planting to minimise the risk of crop damage and the build-up of nematodes,’ said Miss Wood. ‘That’s especially important if crops are close in the rotation, or on light soils where there is additional stress on the plants.’ Growing a PCN resistant variety may also help to limit nematode multiplication, she remarked.

With moderate egg counts (8–15 eggs/g) treatment is highly recommended and growers were urged to consider using a nematicide in combination with a resistant variety. Where high levels of infestation are detected (>15 eggs/g), she advocated considering the use of alternative fields, although levels of up to 30 eggs/g may be acceptable on silts and high organic matter black land.

‘Regular sampling before cropping will help growers track changes in populations and adopt a proactive strategy to prevent build-up to damaging levels. With appropriate management and good stewardship alongside the use of nematicides, the problem of soil pests can be effectively managed,’ she added.

 

For the full article see March/April edition

 

All contents © Copyright Potato Review 2017. All rights reserved
All contents © Copyright Potato Review 2017. All rights reserved