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Sprout suppression series: 3) Maleic Hydrazide

Publication Date: 
7 February 2019

Updated August 2019.

Maleic Hydrazide (MH) is a popular plant growth regulator applied in the field and used to control growth of potatoes in store and those left behind in harvesting operations that might otherwise become volunteers.

It is marketed under a range of brand names, including Fazor, Crown MH, 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 about five 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. Crop should be actively growing. The timing of MH application and its effect on sprout control in storage has been the subject of ongoing trials at two AHDB SPot Farms. Sutton Bridge Crop Storage Research is also investigating the minimum effective dose for 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 for longer term storage when used sequentially with other treatments; for example, when followed by ethylene or an essential oil such as spearmint, or DMN. Recent work as part of an ongoing AHDB-funded trial at Sutton Bridge Crop Storage Research has shown that these types of 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. 

The team at Sutton Bridge Crop Storage Research have recently completed a review on the active substance, which included an industry consultation on the use of MH.

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