Sprout Suppression Series: 2) Spearmint Oil
Spearmint oil has been part of the sprout suppression tool box since it received full UK registration (BIOX-M, MAPP 16021) in 2012 .The active ingredient R-carvone, a terpenoid, is naturally found in spearmint, from which it is extracted. Spearmint oil is marketed as Biox-M in the UK and comes as a volatile oily liquid, usually applied as a hot fog.
Small-scale and commercial trials have demonstrated its efficacy for the fresh pack market and it has been used successfully in some pre-pack supply chains. Spearmint oil can rapidly burn back existing sprouts and has been reported to have been used successfully for ‘recovering’ commercial packing crops in this way.
The warmer temperatures of the processing sector encourage more vigorous sprouting than the cooler temperatures of pre-pack storage and repeat applications are required with consequent cost implications. Recent work (AHDB, S1043) has shown spearmint oil reduces sprout growth in processing crops particularly when used in combination with other sprout suppressants, for example a single low dose of CIPC or maleic hydrazide or both.
While previous research at experimental and semi-commercial scale has shed more light on suitable storage conditions for effective control of sprouting with spearmint oil, further research is required. This will enable the assessment of spearmint oil under different storage situations and therefore provide growers with sprout control strategies to suit their situation. Such research is being conducted by AHDB at SBCSR, the second year of the processing variety trial (S1043) and a newly commissioned study with pre-pack varieties (S1057).