Sprout suppression series: 3) Maleic Hydrazide

We continue with our series on alternatives to CIPC for controlling sprouting in stores. In the last two issues of the Storage Bulletin, we focused on ethylene and spearmint oil. This month, we are turning to the third compound approved for use as a sprout suppressant: Maleic Hydrazide (MH).

MH is a popular plant growth regulator, used to prevent the formation of volunteers in the field, controlling tuber size and shapes.  It is marketed under a range of brand names, including Fazor, Crown, Itcan and Source II. As a sprout suppressant, it has been approved for use in the UK since 1985 and works by inhibiting tuber cell division. Unlike other sprout suppressing chemicals applied at storage, MH is applied as a foliar treatment, usually three weeks before defoliation or natural senescence and is absorbed by leaves before translocation to tubers. It has an MRL of 50 mg/kg.

Because it is used as a foliar spray, its efficacy as a volunteer control and sprout suppressant is determined by its level of uptake, which is ultimately governed by canopy and environmental conditions at the time of application. MH application timings and its effect on sprout control in storage is being investigated at two AHDB SPot Farms. In parallel, Sutton Bridge Crop Storage Research is storing the field trial material to assess the impact of application timing on sprout control in storage.

Research trials have shown that MH as a stand-alone treatment does not always completely prevent sprouting but, providing it is applied correctly, it gives good control in situations when potatoes are stored for short periods and the risk of sprouting is low. It also works well when used sequentially with other treatments, for example, by being applied as an early treatment followed by another. Recent work as part of an ongoing AHDB-funded trial at Sutton Bridge Crop Storage Research has shown that treatment combinations can have a synergistic effect. Treatments combining MH with ethylene or spearmint oil significantly controlled sprout growth to commercially acceptable levels in processing varieties. The trial work is continuing. Similar trials are also being undertaken with fresh-pack varieties.  

How do YOU use maleic hydrazide in your business? Please help us building a robust evidence-base for how MH is used by filling in this questionnaire, the results of which will form part of a review that Sutton Bridge Crop Storage Research is undertaking on the active substance.

While MH looks like a promising option for use as part of sprout control strategies in the future, its challenge lies in the recent change in approval that now prevents MH-treated crops being fed to livestock. This is due to a data gap in the latest round of product reviews that applies to newly-formulated product (material sold on the old label is unaffected). This may, indirectly, lead to MH being removed from use for processing and fresh markets as – until the data gap is satisfactorily closed – MH-treated stockfeed potatoes will have to be segregated for sale. Many businesses are believed to have processes which will prevent this from being done. We recommend you talk to your supply chain to establish their likely position on MH treatment this summer.