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Keeping sprouts at bay

5 November 2014

During September nationwide CIPC Stewardship meetings focused on the new 2014/15 label requirements, Best Practice for CIPC use and the ways alternatives can complement a successful sprout suppression regime.  

In July, the CIPC Approval Holders announced new label rates for 2014/15. These are now 30 grams/tonne for the fresh market and 58 g/t for processing. 
The maximum single dose has reduced been cut to 18 grams/tonne and the minimum interval between treatment and sale for consumption has been extended to 14 days. 
The limit of one treatment on all crops held in cold stores (i.e. at 5°C and below) continues because of slow residue decline at low temperature; a full dose of 18g/tonne is unlikely to be necessary at this temperature if best practice is followed. 
Watch to Adrian Cunnington, chair of Potato Industry CIPC Stewardship Group technical committee discuss improving uniformity, stewardship best practice and an overview of new labels: 
Watch Adrian Briddon, secretary of the Potato Industry CIPC Stewardship Group discuss the practical implications for CIPC use for 2014/15:
Seeking alternatives
This prolonged autumn warm spell has impacted some potato stores with an increasing and concerning number of enquiries coming in about breakdown and sprout control may also be compromised if there is rot present.
However it is crucial store managers stick to the 2014/15 product label and do not exceed the single dose limit in cold stores.
“There are ways store managers can gain enhanced control, whilst reducing associated residues,” says Adrian Briddon. “There are some very interesting alternatives at different stages in the pesticide registration approval process.”
“The new products require a different store management approach and a specific understanding of their application. CIPC is a solid with long-lived residues, added Adrian.  “The new generation of sprout suppressants tend to be either gases or volatile liquids, which gives far more flexibility in building use.”
Stores where CIPC has been previously used, restrict the subsequent use for seed tubers and all other crops. The volatile liquids in the new generation of sprout suppressants will dissipate from store fabrics relatively quickly. Therefore it allows more flexibility and alternative uses of the building after the stored crop has been used.
Sprout suppression by the new products tends to be reversible, with growth resuming as residue levels drop off. Because of a loss of apical dominance, some treatments may have a modifying effect on stem numbers and are being used successfully in seed management. Some of the essential oils available are also reported to control some pathogens.
In Great Britain, CIPC is applied as a hot-fog with a fossil fuel (petrol or LPG) used as the energy source. During the process, ethylene and carbon dioxide are produced from combustion of fuel, which can cause deterioration in processing quality. Therefore, after 6-8 hours when the CIPC fog has settled, fresh air is circulated into the stores to mitigate against any negative impact on fry colour. 
Many of the new sprout suppressants need longer store closure periods after application to ensure complete ‘uptake’ of products from the vapour phase. In many cases twenty four hours is likely to be a minimum label requirement, so for processing store different types of equipment are likely to be used.
Alternatives currently available in the UK
Ethylene has been available for a few years and the companies Restrain and BioFresh currently supply equipment for ethylene control. Ethylene is a gas so losses from store can be relatively high and equipment has to be installed to introduce or generate the gas in store. Sprout control is completely effective in low-temperature stores, with a head-space concentration maintained at around 10ppm. There is little residual effect and sprout control is lost soon after removal from store.
Its application in processing storage is subject to on-going research at SBCSR, primarily to overcome any unwanted effect on fry colour. Sprout control by ethylene is reversible and it is used as a commercial seed treatment for increasing stem numbers in susceptible varieties.
Spearmint oil (active ingredient R-carvone) received full UK registration (Biox-M, MAPP 16021) in 2012. Its use is increasing in pre-pack stores but, in processing stores, is likely to be cost-prohibitive except for niche markets.
As well as being an effective sprout suppressant, spearmint oil can rapidly burn back existing sprouts. Spearmint oil has been reported to have been used successfully on commercial packing crops in this way.
Biox-M is a volatile, oily liquid which is applied by a contractor, as a hot-fog, using a proprietary electric fogger. Sprout control is reversible, with growth resuming when residue levels decline below a critical threshold.
Alternatives that may become available in the UK
1,4-Dimethylnapthalene (DMN) (1,4-SIGHT™) has been available in the United States of America for many years and has now received EU Annex 1 approval, making it available to EU member states. A UK approval is anticipated early in 2015, allowing use on the 2014 crop. It will be contractor applied.
DMN is effective in both pre-pack and processing stores, with potential to replace CIPC. It is a reversible sprout suppressant and can be used to control growth in seed crops (1,4 SEED™). Seed treatments are reported to result in changes to progeny tuber size distributions. It is a volatile, oily liquid and is likely to be applied by contractor as a hot-fog.
3-decen-2-one was identified in research at the University of Washington and is being commercialised by Amvac. It was already approved as a food additive and received US registration as a sprout suppressant (SmartBlock™) in February 2013. It is exempted from an MRL (Maximum Residue Level) in the USA. EU registration trials are currently underway. 3-decen-2-one is a volatile, oily liquid and is likely to be applied by contractor as a hot-fog.
To understand more about the new generation of sprout suppressants call the free storage advice service at SBCSR on 0800 02 82 111. For further information on CIPC, visit the CIPC Stewardship Group Website:
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