J A N U A R Y 2 0 1 9 12 POTATO GROWER Over the past couple of years, I have noticed an increased number of her- bicide injury found in potato fields. These symptoms have come from seed tubers or from the plants being exposed to herbicides. There are many factors that could have caused this noticeable increase in herbicide injury cases. It could be a result of better knowledge of injury symptoms, utilizing different herbi- cides because of glyphosate-resis- tant weeds, not taking proper care to clean tanks, or forgetting to check herbicide use records for soil carryover. Herbicide injury in potato not only can reduce yield, but potato quality often is compromised. Contact her- bicides can disrupt the growth of potato plants, causing potatoes to become malformed. Systemic herbi- cides will travel to the growing points; that is to the newest leaves and to the tubers. For most herbi- cides, when residues are found in the tubers they cannot be sold for food or feed. These translocating herbicides stored in seed potato tubers can also cause negative effects when the seed tubers are planted the following growing sea- son. Common herbicides types that translocate and cause problems in potato are glyphosate, plant growth regulators and ALS-inhibiting herbi- cides. When dealing with plant injury, it is important to identify injury as soon as possible for accurate identifica- tion. Typically, exposure to a low dose of chemical will cause symp- toms that will last for a few weeks. If you wait too long to sample, the herbicides can be difficult to detect, as plants will metabolize, sequester or exude herbicides over time. Record all the information you can about the incident. Things to include would be the date the dam- age was first observed, a map of the showing injury patterns and severi- ty of injury, and the relationship of damaged field to surrounding fields/headlands. Take many high- quality photographs showing injury symptoms of leaves, roots and tubers (Figure 1-3). If you are going to take samples to be sent to a labo- ratory for analysis, use clean gloves and a bag to take a sample of the most injured leaves and/or tubers. Tubers and roots will need to be rinsed with clean water to wash off the soil (this ensures that only plants will be tested for chemical residues and not soil). Place the sample in a box with ice and ship to a reputable laboratory. For documenting herbicide drift, see the NDSU Extension article WC751 “Documentation for Suspected Herbicide Drift Damage” https://www.ag.ndsu.edu/publica- Andy’s Advice: Herbicide Injury In Potatoes By Andy Robinson, Extension Potato Agronomist, NDSU/UMN