Sprout Suppressing Residue Levels of 1,4dimethylnaphthalene (1,4DMN) in Potato Cultivars

Abstract

Research on new sprout control methods led to the discovery of 1,4dimethylnaphthalene (1,4DMN) in the late 1970s. This compound has been registered in the USA since 1996 as a reduced risk chemical for use on stored potatoes for the purpose of sprout suppression. Relatively little is known about the levels of tuber residues required to maintain sprout suppression. The objective of this study was to identify the minimum 1,4DMN tuber residue levels above which sprout growth was inhibited. Using modified steel drums to store and treat potatoes, rates of 0 µL kg−1 to 56 µL kg−1 1,4DMN were applied to non-dormant, slightly “peeping” seed tubers of four different cultivars (Russet Burbank, Russet Norkotah, Shepody and FL1879) stored at 15 C ± 2C. Tubers were treated by dribbling 1,4DMN onto a gauze that was placed on top of a return air pipe that re-circulated forced air inside the drum. Higher application rates resulted in higher 1,4DMN residues and longer suppression of sprout growth. Sprout growth was controlled for more than 50 days for all cultivars in both years for tubers treated at the highest rate. The duration of sprout inhibition corresponded with the time it took for tuber residues to drop below an estimated residue level of 1.4–2.1 ppm, for R. Burbank, Shepody and FL1879, and 2.7 ppm for Russet Norkotah. Below these levels, sprouting was no longer suppressed and resumed for all cultivars.