Volunteer Potato (Solanum tuberosum) Control with Herbicides and Cultivation in Onion (Allium cepa)1

Volunteer potatoes are difficult to control in onions and can greatly reduce onion growth and yield. Herbicides and cultivation were evaluated for control of simulated volunteer potatoes in onions in 1996 and 2000. Three interrow cultivations did not control potatoes in the onion row and the remaining plants reduced onion yield 50 and 73% compared with the hand-weeded checks. Three applications of oxyfluorfen (0.2 + 0.17 + 0.17 kg ai/ha) or bromoxynil plus oxyfluorfen (0.2 + 0.17 kg ai/ha) at the two-, three-, and four- to five-leaf stages of onions followed by a cultivation after each application reduced potato tuber weight 69 to 96% and tuber number 32 to 86% compared with cultivation alone and prevented onion yield loss associated with potatoes. Ethofumesate applied preemergence at 0.6 kg/ha followed by postemergence ethofumesate plus bromoxynil and cultivation reduced potato tuber weight 90% and tuber number 68% compared with cultivation alone, and onions yielded equal to hand-weeded checks. Two applications of fluroxypyr (0.3 kg ai/ha) plus bromoxynil (0.2 kg ai/ha) at the two- and three-leaf stages of onions followed by a cultivation after each application reduced potato tuber weight by greater than 90%, but onion yields were reduced 38 to 66%. Nomenclature: Bromoxynil; ethofumesate; fluroxypyr; oxyfluorfen; onion, Allium cepa L. ‘Fiesta’ and ‘Asgrow EX15120’; potato, Solanum tuberosum L. ‘Russet Burbank’. Additional index words: Groundkeepers (volunteer potato), tillage. Abbreviations: POST, postemergence; PRE, preemergence.