seed treatment of 0.05 oz ProGibb/ton of seed + 0.15 oz Rejuvenate/ton of seed and 4) a seed treatment of 0.05 oz ProGibb/ton of seed + 0.15 oz Rejuvenate/ton of seed followed by a two foliar application of Stimulate (0.05 oz cytokinin/a + 0.03 oz gibberellic acid/a + 0.03 indole-3-butril acid/a) at dime-sized tubers and 10-14 days after dime-sized tubers. We planted Bannock Russet, Dakota Russet, Ivory Crisp, Atlantic, Sangre and Dark Red Norland. What did we find? The treatments did not always work because there was varietal sen- sitivity. Some cultivars responded as we desired, while others did not respond to treatments. Take for example Sangre com- pared to Dark Red Norland. All plant growth regulator treatments caused Sangre to have a quicker emergence, increased stem number (Figure 1), increased tuber count, changed the tuber size profile and slightly increased yield (Figure 2). However, there were no differences in Dark Red Norland from the treatments applied. This is a good example of how each cultivar has a different dose-response to plant growth regulators. Similarly, when we treated Dakota Russet and Bannock Russet, we observed changes in Dakota Russet but not Bannock Russet yield (Figure 3). Another interesting response on certain cultivars was improved length to width ratios, which would be advantageous for increase fry yield on processed potatoes. What does this all mean? Using plant growth regulators as a liquid seed treat- ment can establish a standard usage rate. Plant growth regulators manipulate stem and tuber number and this can be used to improve tuber size profile for the desired use. Plant growth regulator sensitivity is tied to cultivar and seed age. If this is some- thing interesting to you, try experimenting with different rates of plant growth regula- tors until you establish comfort with specif- ic rates on certain cultivars. Figure 1. Effect of plant growth regulator treatments on Sangre and Dark Red Norland emergence and stem number. Figure 2. Effect of plant growth regulator treatments on Sangre and Dark Red Norland yield. Figure 3. Effect of plant growth regulator treatments on Dakota Russet and Bannock Russet yield. F E B R U A R Y 2 0 1 9 POTATO GROWER 13