Sprout Suppression series summary
1,4-dimethylnaphthalene (DMN) is a volatile emitted by potato tubers that naturally inhibits sprouting and induces tuber cells undergoing division to stay at a resting stage. Marketed in synthetic form as 1,4Sight™, it is EU Annex 1 listed and has recently received national registrations in the Netherlands (2015), Austria (2015), Belgium (2017) and Germany, France, Poland and Ireland in 2018.
In Europe it has been used to effectively control sprouting in commercial processing and pre-pack stores. DMN offers flexibility, both in terms of application equipment that can be used and treatment conditions (six doses at up to 20 ml/t each, over the season)*. Because it is a volatile however, stores must remain sealed for 24 to 48 hours post application. Its efficacy when used in combination with other sprout suppressants was highlighted during the EAPR Post-Harvest Section Meeting held in Norwich in March and has also been demonstrated in Sutton Bridge storage trials.
The recent visit to European commercial stores by Sutton Bridge storage specialists (read full story here) has demonstrated the importance of DMN and its use in combination in a post-CIPC scenario. The active is awaiting registration in the UK.
*As per Dutch label. Other European labels may vary.
Orange oil has EU Annex 1 listing and is nearing full registration in Europe. Naturally found in orange peel, it contains the active limonene, which reduces sprouting by burning back active sprouts. Similar to spearmint oil, it is usually applied as a hot fog and stores have to remain sealed between 24-48 hours.
A Belgian project looking to investigate alternative sprout suppressant for the processing and fresh market provides some of the latest insight into orange oil efficacy on European varieties. Efficacy trials have shown that the oily liquid provides similar sprouting control to spearmint oil initially, but that repeated treatment applications become less effective over time. Fry colour was also tested and no negative effects were observed.
Orange oil will be marketed as ‘Argos’ by Arysta Lifesiences and UK registration is anticipated for end of 2019, beginning of 2020.
Available as SmartBlock™ from approval holders Amvac, it is currently only approved for use in USA, Canada and Israel. EU Annex 1 registration is underway.
The volatile-oily liquid is already used as a flavouring additive in the food industry. As a sprout suppressant, it acts on actively growing cells and gives long periods of residual sprout control. Similarly to other sprout suppressant volatiles, it is best applied as a hot fog. Efficacy trials at the French research institute Arvalis have shown that timing of application and temperature conditions in store have an effect on the efficacy of the active. At the lower tested temperature (4 °C), a single application (100 mL/tonne) at dormancy break was sufficient to control sprouting over eight months. At the higher tested temperature (7.5 °C), three application at the same dosage were necessary. Tubers with longer sprouts are likely to require an increased dosage. Trials at Sutton Bridge CSR have shown good efficacy at storage temperatures typical for crisping cultivars.
In the USA, 50 % of the fresh pack market has been reported to be treated with SmartBlock™.