MINNESOTA AREA II POTATO RESEARCH AND PROMOTION COUNCIL AND NORTHERN PLAINS POTATO GROWERS ASSOCIATION 2019 RESEARCH REPORTS Table of Contents 3. Impact of Sublethal Dicamba & Glyphosate Rates on Three Chipping Potato Cultivars M. Brooke, H. Hatterman-Valenti, A. Robinson, G. Secor & A. Auwarter 7. Vine Desiccation as an Effective Disease Management Strategy to Control Verticillium Wilt of Potato N. Gudmestad 13. Nitrogen Fertilization Rate and Cold-induced Sweetening in Potato Tubers During Storage S. Gupta & C. Rosen 21. Pressure Flattening and Bruise Susceptibility Among New Fresh Market and Chip Varieties D. Haagenson 26. Adjuvent Comparison with Potato Desiccants, Grand Forks, 1 H. Hatterman-Valenti & C. Auwarter 27. Adjuvent Comparison with Potato Desiccants, Grand Forks, 2 H. Hatterman-Valenti and C. Auwarter 28. Evaluating SOP vs. MOP Programs in Russet Burbank Potato H. Hatterman-Valenti & C. Auwarter 29. Evaluating Single and Repeat Hail Event in “Clearwater” Potato H. Hatterman-Valenti & C. Auwarter 32. Baseline Evaluation of Pollinator Landscape Plantings Bordering Commercial Potato I. MacRae 36. Management of Colorado Potato Beetle in Minnesota & North Dakota I. MacRae 41. Managing PVY Vectors, 2018 I. MacRae 49. Carryover of Herbicides in Potato Production Systems A. Robinson, E. Brandvik, & P. Ihry 54. Effects of Planting Configuration & Plant Population Density on the N Response of Russet Burbank Tuber Yield & Size C. Rosen, J. Crants, M. McNearney, K. Olander& H. Barrett 66. Evaluation of Aspire, Micro-Essentials S10, & MicroEssentials SZ as Sources of Potassium, Phosphate, Sulfur, Boron & Zine for Russet Burbank Potatoes C. Rosen, J. Crants & M. McNearney 73. Evaluation of New Controlled Release Urea Fertilizer Products as N Sources for Russet Burbank Potatoes C. Rosen, J. Crants, & M. McNearney 85. Evaluation of Polyhalite as a K Source in Russet Burbank Potatoes C. Rosen, J. Crants & M. McNearney 97. Evaluation of a Slow Release Boron Source for Russet Burbank Potatoes C. Rosen, J. Crants & M. McNearney 106. Evaluation of Ivory Russet as Processing Cultivar for Central Minnesota C. Rosen,J. Crants & M. McNearney 118. Data Report for UMN Potato Breeding Program 2018 L. Shannon 133. Potato Breeding and Production for the Northern Plains 2018 Summary S. Thompson 143. Hosting Suitability of Potato & Northern Grown Crops in Rotation with Potato for the Root- lesion Nematode, Pratylenchus penetrans G. Yan, A. KC & A. Plaisance Impact of Sublethal Dicamba and Glyphosate Rates on Three Chipping Potato Cultivars Matthew Brooke, Harlene Hatterman-Valenti, Andy Robinson, Gary Secor, and Collin Auwarter ABSTACT: The recent increase in weedy species resistant to glyphosate has led to the development and release of dicamba resistant soybean varieties. However, with increased utilization of dicamba, herbicide off-target injury has become a major issue for regional farmers. Investigating the impact of drift rates of these two ubiquitous agronomic herbicides, this research explores their effects on three irrigated chipping potato cultivars (Atlantic, Dakota Pearl, and Lamoka) as measured through visible injury, tuber quality reduction, and yield reduction. Herbicides were sprayed at the tuber initiation stage and consisted of dicamba at 99g ae ha-1, glyphosate at 197g ae ha-1, dicamba + glyphosate at 99g ae ha-1 + 197g ae ha-1, and 20 g ae ha-1 + 40 g ae ha-1, respectively, and an untreated control. At seven days after treatment (DAT), high dicamba + glyphosate caused the most damage, with 28% based on visible ratings. Low dicamba + glyphosate was not different from the untreated control. Furthermore, at 21 DAT, visible injury increased to 36% for the high dicamba + glyphosate treatment. The high combination of dicamba + glyphosate resulted in a 60% yield reduction compared to the untreated control, which averaged 1021 cwt ha-1. Tuber specific gravity was also lower for plants sprayed with dicamba. Results from the two field trials suggest that not only can sublethal rates of dicamba + glyphosate greatly decrease potato yields; tuber specific gravity is also reduced, potentially influencing chipping quality. INTRODUCTION North Dakota is a unique and diverse agricultural state. However, soybean is the top crop in North Dakota by acres, with 7.2 million acres planted in 2017 and an estimated value of $2.1 billion (USDA- NASS, 2018). The introduction of dicamba-tolerant soybeans in 2017 provided growers with an option to control glyphosate-resistant weeds. Soybean acres often exist adjacent to other broadleaf crops, such as potatoes, which can be sensitive to dicamba vapor, drift, or spray-tank contamination. In many cases, glyphosate-tolerant crops and now dicamba-tolerant soybeans have been grown next to potatoes. New formulations of dicamba alone or combined with glyphosate have been developed with the goal of reducing dicamba volatilization. Even so, dicamba volatilization was so problematic in 2017 that the North Dakota implemented new dicamba application restrictions (EPA, 2017). It is likely that instances of herbicide drift, vapor drift, or spray tank contamination, and the subsequent injury are going to occur, especially for counties south of I-94, where potato planting often occurs by mid-April. In addition, research has shown cultivar differences to sub-lethal glyphosate rates for russet-skinned and red-skinned cultivars (Crook, 2016), but research has not evaluated white-skinned cultivars. A crop such as potato is unique because it can suffer direct yield losses from dicamba and/or glyphosate drift, and the daughter tubers derived from the mother plants exposed to these herbicides may be severely inhibited when used as seed. Previous research has shown that visible injury to ‘Russet Burbank’ potato can vary by almost 40% for the same sub-lethal herbicide rate that caused nearly twice the total yield loss (Hatterman-Valenti et al., 2017). It was concluded that the less responsive plants (lower visible injury and less total yield reduction) were stressed from higher air temperatures. However, mother plants that displayed less visible injury and less total yield reduction may have transferred more herbicide to daughter tubers considering plant emergence five weeks after planting was significantly reduced when compared to seed from mother plants receiving the same sub-lethal herbicide rates, but during cooler air temperatures. The objective of this research is to determine the impact of sub-lethal dicamba and glyphosate on emergence and graded yield of chipping seed potatoes. This research will benefit potato growers, potato processors, agronomists, and research institutions to understand the effect of dicamba and glyphosate on chipping potato seed tubers. MATERIALS & METHODS Field experiments were be conducted in 2018 at the North Dakota State University (NDSU) Irrigated Research Site, located three miles south of Oakes, North Dakota (46.07 N, -98.09 W; elevation 392 m). This site is irrigated, with an Embden coarse-loamy, mixed, superactive, frigid Pachic Hapludolls soil type (USDA-NRCS, 2017). This makes for very good drainage with large water requirements. This experiment was set up as a randomized complete block design (RCBD) two-factor arrangement, with three cultivars, four replicates, five treatments and two locations in Oakes in both years. Similar experimental methods were used in 2014 and 2015 (Crook A 2016). The treatments consist of a non- treated control, Dicamba (Clarity®, BASF Corporation, Research Triangle Park, NC, 27709), and/or glyphosate (PowerMax®, Monsanto Company, St. Louis, MO, 63167). Dicamba treatments were 99, 20, and 0 g a.e. ha-1. The doses are at 2 and 9% of the field use rate of 1120 g ae ha-1 (Anonymous, 2010). Glyphosate treatments were 197, 40, and 0 g a.e. ha-1. The doses are at 5 and 23% of the field use rate of -1 846 g ae ha . (Anonymous, 2012). (Table 1). Table 1. Glyphosate and dicamba treatments applied to Atlantic, Dakota Pearl, and Lamoka potatoes in Oakes, ND. # Treatment Herbicide rate g ae ha-1 1 Non-treated 0 2 Glyphosate 197 3 Dicamba 99 4 Glyphosate 40 Dicamba 20 5 Glyphosate 197 Dicamba 99 Tuber initiation (TI) was selected on the importance of developing of daughter tubers. Certified Atlantic, Dakota Pearl, and Lamoka seed potatoes were cut into 70g ± 5g seed pieces, insuring that every seed piece had two or more eyes/seed. After the seeds were cut, they were stored for two weeks induce suberization and seed conditioning prior to planting. Each experimental unit (EU) contained two rows with 20 seed pieces planted in each row (40 total seed pieces/EU). All seed tubers were planted 31 cm apart with a 91 cm spacing between each row at 35,880 seed pieces ha-1. The row length was 6.1 m long with a seed depth of 10 cm. A 1.5 m gap of five ‘Red Norland’ potato separated each treatment. Treatments of both dicamba and glyphosate were applied with a CO2 backpack sprayer equipped with a 1.8m boom and four XR11002 flat fan nozzles (TEEJET Spraying Systems Company, Wheaton, IL 60189) 45cm apart at 138kPa and an output of 140 L ha-1. Treatments were applied in progression of lowest to highest dose starting with glyphosate treatments first to mitigate cross contamination of EU’s. The application of these treatments complied with the new 2017 North Dakota rules for dicamba application. The treatments were applied at tuber initiation on June 29th, which is the cutoff date for dicamba in North Dakota. Data was taken throughout the season. Stand count was measured along with ratings for visual control and crop injury will be taken 7 and 21 days after treatment. Additional notes on yield and specific gravity was collected. RESULTS & DISCUSSION The data collected were subjected to analysis of variance using Mixed Model procedure using JMP® Pro 14.0.0 (64-bit) SAS Institute Inc., 100 SAS Campus Dr., Cary, NC 27513). Because the stand was low for Lamoka there was an interaction between rate by treatment. A test of homogeneity of variance between location 1 and location 2 indicated that the environments could be combined.