Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32M A R C H 2 0 1 7 12 POTATO GROWER The recent EPA approval of dicamba-toler- ant soybean and new formulations of dicamba will allow soybean farmers to use dicamba through the R1 growth stage. This means that soybeans can be sprayed until approximately late July in North Dakota and the northern half of Minnesota. This increases the potential for off-target herbicide movement onto sensitive crops, such as potato. Dicamba applications during tuber initiation and early tuber bulking is causing concern for some potato growers. Potato plants that come in contact with dicamba can be severely affected. The first sign of dicamba injury is the twisting, wrinkling, turning and cupping of the leaves, leaflets and petioles (known as epinasty). Similar symptoms are a result of 2,4-D injury, making it difficult to deter- mine the herbicide responsible for injury. These symptoms can occur from a few hours to a week or longer after herbicide exposure. The severity will vary depend- ing on the amount of herbicide and envi- ronmental conditions. Symptoms occur first on the youngest leaf or leaves, because dicamba moves to the growing area of the plant. This also means that dicamba will move to the tubers and roots. As a result, tuber set can be altered, tubers can become malformed with cracks (Figure 1) and/or total yield can be reduced. Additionally, if tubers have dicamba residues, they are not suitable for food or feed. Dicamba residues in seed potato can cause delayed or no emergence the fol- lowing season. Similar symptoms to those mentioned previously can come from dicamba residues in the soil (Figure 2) or from the seed piece (Figure 3). Plant back of potato following the application of dicamba ranges from four months to the next crop- ping season (please check the label on specific dicamba prod- ucts). We have noted that dicamba residues in the seed piece may not be manifested on the first leaf, but can appear later causing confusion of the method the plant con- tacted dicamba (Figure 3). Dicamba can slow emergence of potato plants and reduce leaf area. We are currently studying the effects of dicamba, glyphosate and the combina- tion of dicamba plus glyphosate treat- ments applied on Russet Burbank potato during tuber initiation/early bulking. This is intended to simulate drift of these her- bicides in July. The first thing we have learned is that the environmental condi- tions seem to greatly affect the amount of dicamba taken up by the plant. As a result, in Oakes, North Dakota there was significant yield loss following dicamba + glyphosate while at Inkster, North Dakota there was no significant yield loss. Andy’s Advice: What Potato Growers Should Know About Dicamba By Andy Robinson, Extension Potato Agronomist, NDSU/UMN and Harlene Hatterman-Valenti, NDSU Figure 1. Growth cracks and malformations as a result of dicamba applied during tuber initiation/early bulking on Russet Burbank tubers. Figure 2. Effects of planting Red Norland potato follow- ing soil treatment of dicamba. Note the epinasty in the leaves and the cracking in the young tuber (inset picture).