Management of volunteer potato is difficult and requires an integrated approach. Soil fumigation is one tactic known to reduce population densities of certain weeds and may be a method to improve the management of volunteer potato. The effect of 1,3-dichloropropene (1,3-D) and metham sodium on potato tuber viability was tested in sealed glass jars at various doses, incubation temperatures, and times of exposure. Tuber viability data were fitted to a logistic model, and I 90 doses (90% suppression) were calculated for each combination of temperature and time of exposure. I 90 doses for 1,3-D ranged from 41 to 151 kg/ha and from 96 to over 480 kg/ha metham sodium. Both nondormant and dormant tubers were injured by exposure to metham sodium. Soil fumigation with 1,3-D and metham sodium has the potential to greatly reduce the number of viable potato tubers.

Volunteer potato is highly competitive with onion and few control tactics are effective for removing this weed from an onion crop. Both volunteer potato density and duration of interference reduce onion yield, but the interaction of these factors is unknown. Field trials were conducted in 2003 in Idaho, Oregon, and Washington to determine the influence of volunteer potato density on the critical time of weed removal (CTWR) in onion. Yield losses of 2.5, 5.0, and 10% were estimated to occur at 534, 654, and 830 growing degree days (GDD) after onion emergence, respectively, with a volunteer potato density of 0.5 plants/m2. At 2.0 volunteer potato plants/m2, yield losses of 2.5, 5.0, and 10% were estimated to occur at 388, 481, and 598 GDD after onion emergence, respectively. Volunteer potato at 2.0 plants/m2 had to be removed at least one onion leaf stage sooner, compared to a weed density of 0.5 plants/m2, to avoid yield loss. Yield loss due to volunteer potato density or duration of interference was greatest among jumbo, colossal, and supercolossal market grades (P ≤ 0.1). Lowering potato tuber density in crops preceding onion will extend the critical time for weed removal and reduce the risk of crop loss.

Volunteer potato can be a host of serious pest problems in potato and could provide a source of inoculum for subsequent potato crops. Volunteer potato can also be difficult to control in many rotational crops. Potato shoots were removed once, twice, and throughout the growing season, beginning at early and late tuberization. Compared with no shoot removal, two or more shoot removal treatments reduced the number of tubers 42% or more. A single shoot removal treatment at early tuberization reduced tuber biomass 37%, compared with 65% when shoot removal was initiated several weeks later. Regardless of timing, a single shoot removal increased the number and biomass of small tubers (≤ 57 g each). Control tactics that remove or kill volunteer potato shoots require repeated application or integration with other management practices to suppress the weed.