Chemical vine desiccation of two potato cultivars

Russet Burbank and Onaway potato (Solanum tuberosum L.) vines were desiccated with diquat (6,7-dihydrodipyrido (1,2-a:2′1′-c) pyrazinediium ion), ametryn (N-ethyl-N-methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine), paraquat (1,1′-dimethyl-4,4′-bipyridinium ion), and endothall (7-oxabicyclo (2.2.1) heptane-2,3-dicarboxylic acid) applied at various rates alone or combined with surfactants, drift retardant, copper, or ammonium sulfate. Diquat and paraquat at 0.28 and 0.56 kg ha^?1 plus nonionic surfactant thoroughly desiccated Onaway and Russet Burbank potato vines. Only Onaway vines were thoroughly desiccated by ametryn at 1.3 and 2.3 kg ha^?1. Endothall at 0.87 kg ha^?1 provided thorough desiccation of Russet Burbank vines. The addition of a drift retardant did not reduce the effectiveness of diquat, while combining either ammonium or copper sulfate with diquat slowed the dieback of potato vines in 1987. Combining copper sulfate with diquat also slowed the dieback of Onaway vines in 1988. Both copper and ammonium sulfate, combined with diquat and nonionic surfactant, slowed the dieback of Russet Burbank vines when evaluated two days after application, but seven days later, no difference in vine dieback was evident. Crushing plants by rolling the field prior to desiccant application quickened vinekill by 18%. Applications of diquat using flat fan nozzles at 333 kPa provided vinekill equivalent to applications using hollow cone nozzles on a 25 cm spacing at 833 kPa, when spray volume for both applications was 467 L ha^?1. Potato yield, percentage of U.S. No. 1 potatoes, and stemend discoloration were unaffected by chemical desiccation.