Potato Variety Tolerance to Flumioxazin and Sulfentrazone

Field studies were conducted at Aberdeen, ID; Ontario, OR; and Paterson, WA, to evaluate potato tolerance to flumioxazin and sulfentrazone. In ‘Russet Burbank’ tolerance trials conducted in 2000 at ID, OR, and WA, sulfentrazone applied preemergence (PRE) at rates ranging from 105 to 280 g ai/ha caused significant injury consisting of stunting, leaf discoloration-blackening, and/or leaf malformation-crinkling at 4 wk after treatment (WAT). By 12 WAT, injury was ≤5%. At 4 WAT, flumioxazin applied PRE at 105 and 140 g ai/ha resulted in injury, whereas 53 g ai/ha did not cause significant injury. At 12 WAT, no visual injury was present at the ID site, whereas flumioxazin at 140 g/ha was still causing injury in WA. Regardless of initial injury, Russet Burbank tuber yields at ID, OR, and WA were not reduced as a result of any flumioxazin or sulfentrazone treatment compared with the nontreated controls. In potato variety tolerance trials conducted at ID in 2000 and at WA in 2002 with Russet Burbank, ‘Ranger Russet’, ‘Russet Norkotah’, and ‘Shepody’ and at ID in 2002 with those varieties plus ‘Alturas’ and ‘Bannock Russet’, early season injury caused by flumioxazin or sulfentrazone applied PRE at rates as high as 210 g ai/ha or 280 g/ha, respectively, occurred, but variety tuber yields were not reduced compared with nontreated control yields. In contrast, at ID in 2001, early injury caused by flumioxazin or sulfentrazone applied PRE at 105 or 210 g/ha translated to tuber yield reductions of all six varieties tested compared with the nontreated controls. At WA in 2001, Ranger Russet tuber yields were reduced by PRE applications of flumioxazin at 53 to 140 g/ha or sulfentrazone at 105 to 280 g/ha, and Shepody total tuber yields were reduced by all rates of PRE-applied sulfentrazone. Russet Burbank and Russet Norkotah tuber yields were unaffected by either herbicide. Unusual heat stress occurring early in the 2001 growing season at both locations may have compounded the effects of herbicide injury and, consequently, tuber yields were reduced in 2001, whereas injury occurring in 2000 or 2002 during relatively normal growing conditions did not translate to yield reductions.

Potato Tuber Yield, Mineral Concentration, and Quality after Calcium Fertilization

In a 3-year study on a fine sandy loam soil, `Atlantic' (1989), `Frontier' (1990-91), and `Russet Burbank' (1989-91) potato (Solanum tuberosum L.) response to rate and time of Ca fertilization was evaluated. Calcium was applied preplant at 0, 90, 180, and 270 kg·ha-1 as CaSO4 and side-dressed at 0, 34, and 68 kg·ha-1 as Ca(NO3)2, with treatments combined in a complete factorial. Preplant Ca fertilization increased soil Ca concentration each year. Calcium fertilization did not affect tuber yield or grade distribution. Tuber concentrations of P, K, and Ca in `Russet Burbank', Ca in `Frontier', and S in all cultivars increased with increasing preplant Ca rate. `Russet Burbank' tuber P, K, Ca, and Cu concentrations and `Frontier' tuber S concentration increased as side-dressed Ca rate increased. Tuber concentrations of most nutrients decreased between midseason and harvest. The incidence of internal brown spot (IBS) was very low in `Atlantic' and `Russet Burbank' tubers and was reduced in `Atlantic' by preplant Ca application. In 1990, IBS severity and incidence in `Frontier' were reduced by preplant and side-dressed Ca fertilization. In 1991, after 4 months of storage at 7C, severity and percentage of tubers with IBS were reduced by preplant and side-dressed Ca fertilization. During storage, IBS decreased in `Russet Burbank'. Brown center in `Russet Burbank' decreased as side-dressed Ca rate increased. In 1990, `Russet Burbank' french-fry color improved as preplant Ca rate increased.

Reduction of Pratylenchus penetrans in potato tubers treated with oxamyl and sodium hypochlorite

Soaking potato (Solanum tuberosum 'Russet Burbank') tuber halves for 1 h in sodium hypochlorite (1% available chlorine) or for 20 min in a 32 mg mL−1 solution of oxamyl (24% liquid) reduced the number of root-lesion nematodes (Pratylenchus penetrans) in the peel by 92 and 88%, respectively, relative to untreated tuber halves extracted in a mist chamber for 2 wk. Treated tuber halves were grown in pots for 8 wk in the greenhouse. There was no phytotoxicity in the plants that emerged although sodium hypochlorite may have inhibited plant emergence; both treatments reduced the number of days required for plant emergence by 3–6 d. In general, both chemicals increased plant growth. Oxamyl was completely effective in preventing a nematode infestation of the soil; sodium hypochlorite was ineffective. On average, only a single specimen of P. penetrans was recovered from the oxamyl-treated root system vs. 835 in the sodium hypochlorite treatment. No P. penetrans was recovered from the oxamyl-treated original seed-piece after 8 wk whereas an average of 427 and 329 half-tuber−1 were present in those treated with water or sodium hypochlorite, respectively. The data suggest that a 20-min immersion of P. penetrans-infested potato seed pieces in oxamyl is extremely effective in preventing soil infestation by the nematode. Key words: Bleach, disinfection, potato, Pratylenchus penetrans, root-lesion nematode, Solanum tuberosum