Chlorpropham (CIPC) – the active ingredient used to inhibit sprouting in stored potatoes – has not been renewed by the European Commission. The decision was made on June 17 and comes into effect 20 days after that decision – July 8.

This means the product will be withdrawn on January 8, 2020, and cannot be used from October 8, 2020.

Looking towards future seasons Haggard Stores in north Co. Dublin went in search of an alternative and trialed 1,4 Sight this autumn on Ivan Curran’s farm in Co. Meath.

The product contains one ingredient – Dimethylnaphthalene (DMN), which is given off by potatoes naturally.

Why is a sprout inhibitor needed?

According to Stephen McCabe of Haggard Stores, 10-15% of the 10,000ha of potatoes grown in Ireland are grown for processing. Approximately 35,000t of these processing potatoes are stored for longer than two months and above 6° each year.

If potatoes are stored below 6° they will produce reducing sugars, which will result in poor cooking colour in crisps and chips.

However, storing at this temperature means potatoes are subject to sprouting, which also results in a reduction in quality. The majority of potatoes stored in this country are chemically treated to prevent sprouting in storage. As CIPC is now being phased out an alternative product is needed.

New product

DMN was discovered in Glasgow in the 1980s and has been used in the US, Canada and New Zealand since the mid-1990s. The products was used on its own, but also to reduce CIPC inputs.

Similar to CIPC, DMN is applied as a vapour.

How it works?

Stephen explained that 1,4 Sight penetrates through the skin of the potato and works internally to restore dormancy. This in turn lowers the respiration rate, slows down the loss of moisture and solids and diminishes shrinkage and susceptibility to bruising.

A number of growers attended a recent workshop on the product – which was organised by Haggard Stores – and had the chance to see how the product worked on Ivan Curran’s store of Sassy potatoes.

The rates of the product used were based on crop observations at the time.

Store management:
  • Applied using a Synofog Electric fogger;
  • Entered storage on October 24, 2018;
  • 5 applications of 1,4 Sight;
    • October 24 – 20ml/t;
    • November 29 – 14ml/t;
    • December 27 – 20ml/t;
    • January 28 – 15ml/t;
    • April8 – 10ml/t;
  • Total application of 79ml/t over the season.

Stephen reported: “There were no visible signs of any sprouting in the store. Sugar levels measured during the period all came back low.”

A Synofog Electric fogger was used to apply the product

Ivan commented that the product has performed very well given the challenging conditions it faced as potatoes entered storage last autumn.

As well as constant monitoring, early treatment is essential to keep potatoes dormant, particularly in a warmer season like 2018 when sprouting was more advanced than other years.

The potatoes will not come out of storage until July and at this time total weight loss in store and final sugars will be measured.

“Against an ever diminishing arsenal of chemical options that growers have at their disposal, it is comforting to know that there is a clean and effective replacement for CIPC for potatoes in store. 1,4 Sight will be available for use across Ireland for the coming autumn,” Stephen concluded.