The impact of dill weed, spearmint and clove essential oil on sprout suppression in potato tubers

Abstract

Sprout control is essential for successful management of stored potatoes. This study examined the effect of dill weed, spearmint and clove essential oils on sprouting of potatoes. Extracts of steam distilled dill weed whole plants containing 41.5-42.7% of S-(+)-carvone and spearmint foliage extracts containing 97.2-97.6% of R-(-)-carvone, were applied to tubers in a series of experiments using either 1-L glass jars or 63-L steel drums. The composition of the essential oils was consistent between years but evaporation rate varied among the oils as dill weed extract evaporated the fastest while clove oil evaporated the slowest under the same conditions. After exposure to essential oil treatments, tuber sprout number and weight were assessed and compared to untreated control and tubers treated with commercially marketed clove oil product (Biox-CTM, containing 78.5-82.3% eugenol). Applications of 32.5 and 47.6 mg L-1 headspace of dill weed oil and 21.5 and 22.3 mg L-1 headspace of spearmint oil achieved 50% reduction in 'Russet Burbank' sprout weight and sprout number respectively, 30 days after the initial treatment. Tubers stored in environments with 60-240 mg L-1 headspace of dill weed or spearmint oils suppressed sprouting at least 5 weeks longer than that of the controls. In 63-L steel drums, repeated dill and spearmint oil vapor treatments effectively and consistently suppressed sprouting of 'Russet Norkotah' and 'Piccolo' tubers for 7-8 months when doses were 25 mg L-1 headspace or higher and when treatments were repeated at least every four weeks. Within this range, sprout suppression was not sensitive to treatment variations, and, therefore, an optimal treatment level could not be determined. Clove oil was less effective in suppressing sprouting, likely due to its slower vaporization compared to dill and spearmint oils. Essential oil treatment effects on seed tuber viability were evaluated on 'Piccolo'. Tubers were planted after exposure to dill or spearmint oil vapor environments ranging from 15-240 mg L-1 headspace for seven days. There were no adverse effects on seed viability at doses less than 120 mg L-1 headspace. Although environments with