Hydrothol as a Vine Desiccant of ‘Atlantic’ Potatoes

ABSTRACT Desiccating potato (Solanum tuberosum L.) vines using herbicides is a common practice but current desiccants are not satisfactory. The objective of this study was to evaluate hydrothol, the mono-amine salt of endothall, as a vine desiccant on ‘Atlantic’ potato. Hydro-thol was applied at 0.56 to 1.68 Kg ai/ha, endothall at 1.12 Kg ai/ha and diquat at 0.28 Kg ai/ha. Split applications of hydrothol were compared to single doses. Subjective evaluations were made on regrowth and tuber skinning, and objective measurements of specific gravity and yield were measured. Trials were conducted from 1991 to 1995 at Scottsbluff, NE. The optimal rate of hydrothol was 1.12 Kg/ha for leaf desiccation but was no more effective than endothall or diquat at their standard rates. There was a linear dose response for stem desiccation, but the highest hydrothol rate, 1.68 Kg/ha, was less effective than endothall. None of the hydrothol rates improved tuber skinning over endothall or diquat. Regrowth after hydrothol treatment was similar to the check and diquat, but endothall stimulated regrowth more than other treatments. Rates of hydrothol below 1.68 Kg/ha, endothall and diquat did not adversely affect specific gravity of harvested tubers, and there was no significant effect on yields. Split applications of hydrothol resulted in slower leaf desiccation than single applications, and stem desiccation was greater with a single application of hydrothol than with split applications. The addition of ammonium sulfate, 11.2 Kg/ha, to hydrothol at 1.12 to 1.68 Kg/ha increased stem desiccation but also increased regrowth. Although hydrothol may be used as a vine desiccant, the addition of ammonium sulfate may be needed to achieve a level of commercially acceptable activity.