Rhizoctonia infection in potato crops could seriously reduce the value of processing crops. Growers are urged to use new techniques to minimise infection and produce quality products with more even colour and better taste.
With the BPCâs inspirational Love Chips campaign culminating in the National Chip Week this month (Feb 12 - 18), potato growers are being encouraged to raise the quality of the processing crop, and ensure that they are helping to protect the market that currently uses one in every three potatoes grown in the UK*.
âFor too long the processing crop has been considered the poor relation to the pre-pack trade,â according to Syngenta Potato Manager, Simon Parker. âYet the quality of the processed product is entirely dependent on the quality of the potatoes going into the factory or chip shop.â
In recent years processed crop consumption has exceeded fresh potato sales. Over 10% of the UK potato crop is supplied direct to the countryâs 10,000 chip shops, making fish and chips by far the nationâs favorite take-away meal*.
Food industry research has pinpointed the essential roles of tuber dry matter and reducing sugar content in producing chips with the perfect crispness and colour. If dry matter is too low, chips absorb too much oil and become soft and greasy - as well as increasing frying costs; too high a dry matter stops chips absorbing sufficient oil to get the all important taste. The reducing sugar content is an important factor in determining the colour of the fry.
âProcessors can, to some extent, adjust the length of fry time, temperature and oil composition, but the crucial factor for quality products is to have a consistent throughput of identical quality potatoes,â reports Mr Parker.
He advocates better control of Rhizoctonia solani (Black Scurf) when planting processing crops, would result in more even tuber size and maturity at harvest - with benefits of more consistent dry matter and reducing sugar content.
âWe know from extensive field trials and growersâ experience with Amistar that we can reduce the impact of Rhizoctonia on crops, and produce a more even tuber size in the pre-pack potato crop. We believe it could have the same advantages for growers supplying the processor market, including chips, crisps and other value-added products.â
This season Syngenta Potato has instigated a new research project with Cambridge University Farms, to further investigate the potential for Rhizoctonia control with Amistar to enhance the quality of the processing crop.
David Firman of CUF reports its trials have already shown the opportunities to achieve more consistent tuber size with Amistar application in furrow at the time of planting. In previous CUF trials, Amistar successfully narrowed the tuber size spectrum, producing a 12% increase in the important 40-90mm size band, calculated to be worth an additional ÂŁ300/ha for the processing market.
âRhizoctonia infection has been associated with increased sugar levels and darker fry colour. This project will assess the opportunities for Amistar to enhance both the consistency of tuber size and improved tuber quality for the processing industry over the coming seasons,â he adds.
Syngenta Technical Manager, Michael Tait, highlights that crops planted into Rhizoctonia affected soil are usually slower to emerge and sometimes patchy due to the effects of the disease. Although the leaf canopy size can catch up, the shorter growing season inevitably leads to greater diversity in tuber maturity and size.
Furthermore, Rhizoctonia stem pruning can lead to secondary tuber initiation, with a late flush of small tubers, which do not have the time or plant reserves to reach marketable size or consistent maturity. Secondary tubers also divert energy from early tubers on the same plant - reducing overall marketable yield, and can increase volunteers in following crops if left behind at harvesting. âAmistar significantly reduces stem and stolon canker caused by Rhizoctonia, which is a major contributor to secondary initiation and tuber variability,â claims Mr Tait.
Furthermore, Mr Tait points out that Rhizoctonia infection can also lead to an increase in misshapen and knobbly potatoes - both of which cause high levels of wastage for processors. âWith increasing costs and environmental implications of waste disposal, processors are looking to minimise losses from peeling rejects, which Amistar could help to reduce.
âControl of soil-borne skin diseases such as Black Dot, with the use of Amistar, could help minimise the depth of peeling required - further cutting waste and improving product yield from the crop,â he adds. Research trials have shown that Amistar can also give a useful reduction in Silver Scurf, which could help to reduce in-store losses and the effects of disease development on tuber dry matter - thereby helping to improve the quality of the crop destined for longer term storage before processing.
Defra crop monitoring studies have shown an average 58% of UK crops are affected by Rhizoctonia. The regional incidence of the disease is universal, with crops in the north worst particularly affected.
Simon Bowen of leading potato suppliers, Solanum, maintains the company has always believed quality starts in the field, not in the packhouse or factory. âWe know that agronomy can have a major impact on the taste and quality of the crop. Rhizoctonia is one of the factors that has a major bearing on the consistency of tubers; greater consistency can only help the eating experience and satisfaction of consumers.â
Mr Bowen highlights that dry matter and sugar content will affect the cooking quality of tubers for boiling, mash and roasting, as well as chips. Just a couple of per cent variation in dry matter between tubers can make an enormous difference in the cooking time for micro-waved new potatoes, for example; âAnd that can be the difference between a consumer coming back for more, or switching to pasta,â he adds.
âFor too long the industry has concentrated on the appearance of tubers, possibly to the detriment of taste and cooking characteristics. Any initiative that can address these elements and produce better quality potatoes that will increase consumer demand is very welcome.â
Simon Parker adds: âWe believe there are real opportunities for UK processing potato growers to achieve the same yield and quality benefits from Amistar already enjoyed by pre-pack and ware crop producers.â
* Statistics from BPC âLove Chipsâ campaign. National Chip Week is organised by the British Potato Council, with a series of promotional events and activities, running from 12 - 18 Feb. For more information visit the web site www.lovechips.co.uk