Methods to Reduce Sprouting and Emergence of Fresh Potatoes Destined for Export Markets

Exporting potatoes include regulations aimed at minimizing phytosanitary risk. Fresh potatoes may pose a risk if advertently or inadvertently planted; therefore, sprout control programs need to be developed to ensure minimal sprout and subsequent plant development. A two-year study with Russet Norkotah and Agata was established to assess how sprout inhibitor programs affect sprout development, emergence, and yield. Treatments included: 1) non-treated control, 2) maleic hydrazide (MH) foliar applied the previous season (12.7 L/ha) followed by dimethylnapthalene (DMN; 20 ppm) application within two to four weeks of planting, 3) thermal aerosol chlorpropham (CIPC, 20 ppm) applied 70 days after harvest, 4) MH plus thermal aerosol CIPC (20 ppm), 5) thermal aerosol CIPC (20 ppm) plus spray CIPC (10 ppm) within weeks of planting, and 6) MH plus thermal aerosol CIPC (20 ppm) plus spray CIPC (10 ppm) within weeks of planting. Potatoes (n=15, 4 replicates) were assessed for sprout development in storage prior to planting. Treated potatoes were planted in Kimberly, ID in 15.2-meter plots (n= 55 seed pieces; 5 replicates). Emergence, yield, and grade were evaluated. During storage, dormancy break did not occur or was delayed for tubers treated with CIPC and/or MH. In the field, emergence was delayed by all sprout inhibitor treatments, and inclusion of thermal aerosol CIPC in the treatment program was the most effective delaying emergence up to 50 to 80 days after planting. In treatment 6, less than 10% of emergence was observed 90 days after planting for both cultivars. Due to extreme delays in emergence with the treatments, 60 to 98% lower yields were observed for treatments that included CIPC compared to the non-treated control. Sprout inhibitor programs should include CIPC to ensure minimal sprouting for export market regulations.