DEVELOPMENT OF HERBICIDE OPTIONS FOR WEED CONTROL IN POTATOES

Transcription

1 DEVELOPMENT OF HERBICIDE OPTIONS FOR WEED CONTROL IN POTATOES Corey V. Ransom and Joey K. Ishida Malheur Experiment Station Oregon State University Ontario, Oregon, 1999 Introduction In 1999, four trials were conducted to evaluate new herbicides for weed control efficacy and potato tolerance. In all, 42 different herbicide treatments were investigated. These trials demonstrated that potatoes are tolerant to much higher rates of sulfentrazone than are necessary to achieve acceptable weed control. Potato tolerance to BAS H and Dual Magnum was demonstrated, and yields were not reduced even when BAS H and Dual Magnum were applied at two and four times the typical use rates. Postemergence combinations of Dual Magnum with or were shown to cause significant foliar injury, and the combination reduced marketable tuber yield. Under favorable environmental conditions, most of the herbicides evaluated provided exceptional weed control. Postemergence applications of Select provided good volunteer barley control without injury to the potatoes. Many of the herbicides investigated have promise for improving weed control in potatoes in the future. Procedures Four trials were conducted at the Malheur Experiment Station to evaluate new herbicides for weed control efficacy and crop tolerance in potatoes. A trial evaluating postemergence grass herbicides for volunteer barley control was furrow irrigated while the other trials were sprinkler irrigated. The sprinkler irrigated trials were planted April 13 in a silt loam soil with ph 7.8 and 1.5 percent organic matter. The volunteer barley control trial was planted April 15 in a loam soil with ph 8.0 and 1.1 percent organic matter. For all trials, 'Russet Burbank' seed pieces were planted every 9 inches in 36- inch-wide rows. Experimental plots were four rows wide and 30 ft long. Plots were sidedressed with fertilizer on April 22, and beds were reshaped with a lilliston on April 23. Preemergence herbicides were applied April 30 and immediately incorporated with overhead irrigation. Postemergence applications were made June 4. Treatments were applied with a CO 2-pressurized backpack sprayer delivering 20 gpa at 30 psi. Plots were irrigated with sprinklers according to crop requirements throughout the season. Potato injury and weed control were evaluated throughout the season, and tuber yields were taken by harvesting the center two rows of each plot. Potatoes were harvested on September 20, 21, and

2 Potato Response and Weed Control with Sulfentrazone Combinations Sulfentrazone was applied alone at rates from to lb ai/acre and at lb ai/acre in combinations with other herbicides including,, Eptam, Dual II Magnum, BAS H, and Prowl. Treatments were replicated four times. Preemergence Herbicides for Weed Control in Russet Burbank Potatoes In this trial, treatments included combinations of different herbicides including BAS H, Dual Magnum, Frontier, Eptam, Prowl,, and. Treatments were replicated three times. All treatments were applied preemergence, except for Dual Magnum combinations with either or, which were applied at the postemergence application time. Tolerance of Russet Burbank Potatoes to BAS H This trial was conducted to evaluate BAS H for crop injury at normal field use rates and at twice and four times the normal rate, and to compare it to other standard herbicides applied at twice their labeled rates. BAS H is an active isomer of the herbicide Frontier (dimethenamid) and has been submitted to EPA for registration on potatoes. Treatments were replicated four times. The potato canopy covered the rows early this year, keeping us from hand weeding the plots. At the end of the season, weeds were apparent in some plots, but competitive effects were negligible. Volunteer Barley Control with Select Volunteer barley was broadcast over the entire trial on April 22. Prowl (0.75 lb ai/acre) was applied April 23 and incorporated with the lilliston. The lilliston also incorporated the barley seed. Prowl was used to control other weeds without having much impact on the barley. Grass herbicides were applied on June 4 when potatoes and barley both averaged 9 inches in height. Treatments were replicated four times. Potato injury and barley control were evaluated until the potato canopy outgrew the barley. potato yield was determined by harvesting the center two rows of each plot, but tubers were not graded. Results, Discussion, and Conclusions In 1999, the spring weather was cool and dry and then warmed up shortly after planting. Potatoes emerged and quickly formed a canopy while weed germination was low. The low weed germination and early potato canopy resulted in excellent weed control from almost all of the preemergence herbicide combinations evaluated. Potato Response and Weed Control with Sulfentrazone Combinations Sulfentrazone alone and in combination with other herbicides did not cause significant potato injury (Table 1). All of the treatments provided at least 87 percent control of redroot pigweed, common lambsquarters, and hairy nightshade. Barnyardgrass was not present at high enough populations to be evaluated. Sulfentrazone at the lowest rate evaluated provided at least 99 percent control of all three weed species. alone provided slightly less redroot pigweed control than the other treatments. On 155

3 September 1, alone and plus had slightly lower control of common lambsquarters and hairy nightshade than the other treatments, except for alone. tuber yields were not different among treatment (Table 2). All treatments increased U.S. Number One and total marketable tuber yields in comparison to the untreated check. Sulfentrazone plus Dual II Magnum had higher U.S. Number One and total marketable yields than sulfentrazone at the highest rate (0.375 lb ai/acre), sulfentrazone plus or or Eptam, plus, and alone. The results suggest that potatoes are tolerant to sulfentrazone at rates higher than needed for effective weed control. Preemergence Herbicides for Weed Control in Russet Burbank Potatoes Postemergence applications of Dual Magnum in combination with or caused significant foliar injury, with the injury being more severe with the Dual Magnum plus combination (Table 3). None of the preemergence treatments caused visible injury. Injury from the postemergence treatments became less apparent as the season progressed. On June 15, Dual Magnum applied preemergence and Dual Magnum plus applied postemergence provided the least control of redroot pigweed. The postemergence combination improved as the season progressed, but the preemergence application of Dual Magnum still had only 80 percent redroot pigweed control on September 1. All other treatments provided greater than 90 percent redroot pigweed control. Common lambsquarters and hairy nightshade control was also poor with the postemergence application of Dual Magnum plus at the early evaluation, but was among the best by the September evaluation. BAS H plus, Prowl plus, and alone had greater than 95 percent control of redroot pigweed, common lambsquarters, and hairy nightshade throughout the entire season. All treatments increased total yields (Table 4) compared to the untreated check except for Dual Magnum plus. The reduced total yield may have been due to the severe injury early in the season. Prowl plus and Eptam plus had among the highest yields of U.S. Number One and total marketable tubers while Dual Magnum alone preemergence and Dual Magnum plus postemergence were not different from the untreated for total marketable yield. Prowl plus yielded higher than Prowl plus for total U.S. Number One and total marketable potato yields. Prowl plus (167 cwt/acre) produced more undersize tubers than plots treated with Prowl plus (139 cwt/acre). Slightly lower weed control with the Prowl and combination may have resulted in the lower yields. Tolerance of Russet Burbank Potatoes to BAS H No potato injury or differences in potato yield and quality were observed when BAS H, Frontier, Dual II Magnum, and Prowl were applied at twice the labeled field rate (Table 5). Even at 4 times the typical use rate, BAS H and Dual II Magnum did not cause significant injury or reduce potato yields. These results suggest that potato tolerance to the herbicides evaluated is very high. Although not significant, low weed pressure in the untreated check may have depressed yields for that treatment. 156

4 Volunteer Barley Control with Select Herbicide activity was slow because the barley was so large when the postemergence treatments were applied. On June 18, barley control (Table 6) was greatest with Select at the high rate (0.188 lb ai/acre). Poast alone and Select combined with provided the least control. The addition of to Select appeared to decrease early control. However, by June 23, barley control was similar for all Select treatments but lower with Poast. All herbicide treatments increased potato yield compared to the untreated check. Select would be useful for postemergence control of volunteer barley and other grass species in potatoes. 157

5 Table 1. Weed control and potato injury on June 15 and September 1 with sulfentrazone combinations, Malheur Experiment Station, Oregon State University, Ontario, Oregon, Weed control Potato Injury Redroot pigweed Common lambsquarters Hairy nightshade Treatment Rate lb ai/acre % Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone + Eptam Sulfentrazone + Dual II Magnum Sulfentrazone + BAS H Sulfentrazone + Prowl Eptam Sulfentrazone Untreated LSD (0.05) NS

6 Table 2. Russet Burbank tuber yieldt and grade in response to sulfentrazone combinations, Malheur Experiment Station, Oregon State University, Ontario, Oregon, U.S. Number One Treatment Rate 4-6 oz 6-12 oz > 12 oz % no. 2 marketable yield lb ai/acre cwt/acre % cwt/acre Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone Sulfentrazone Eptam Sulfentrazone Dual II Magnum Sulfentrazone BAS H Sulfentrazone Prowl Eptam Sulfentrazone Untreated LSD (0.05) NS NS NS 44 4 NS 45 NS tpotatoes were harvested on September 21 and

7 Table 3. Potato injury and weed control with preemergence and postemergence herbicide applications, Malheur Experiment Station, Oregon State University, Ontario, Oregon, Weed control Injury Redroot pigweed Common lambsquarters Hairy nightshade Treatment Rate Timing lb ai/acre ok Frontier PRE BAS H PRE BAS H PRE BAS H PRE Prowl Prowl + Eptam PRE Prowl PRE Prowl PRE Eptam PRE Eptam PRE Dual Magnum POST Dual Magnum POST Dual Magnum 1.6 PRE PRE PRE PRE Untreated LSD (0.05)

8 Table 4. Tuber yieldt and quality in response to preemergence and postemergence herbicide applications, Malheur Experiment Station, Oregon State University, Ontario, Oregon, Treatment Rate Timing U.S. Number One 4-6 oz 6-12 oz > 12 oz no. 2 marketable yield lb ai/acre cwt/acre % cwt/acre Frontier PRE BAS H PRE BAS H PRE BAS H PRE Prowl Prowl + Eptam PRE Prowl PRE Prowl PRE Eptam PRE Eptam PRE Dual Magnum + Dual Magnum POST POST Dual Magnum 1.6 PRE PRE PRE PRE Untreated LSD (0.05) NS 38 NS 51 5 NS t Potatoes were harvested on September

9 Table 5. Potato injury and yield t in response to preemergence herbicide applications, Malheur Experiment Station, Oregon State University, Ontario, Oregon, Treatment Injury U.S. Number One Rate Field rate oz 6-12 oz >12 oz Two's Marketable Yield lb al/acre cwt/acre % -----cwt/acre Frontier X BAS H 0.64 lx BAS H X BAS H X Dual II Magnum 2.6 2X Dual II Magnum 5.2 4X Prowl 3 2X Untreated LSD (0.05) NS NS NS NS NS NS NS NS NS NS -p otatoes were harvested on September 21 and 22. Table 6. Volunteer barley control with postemergence grass herbicides, Malheur Experiment Station, Oregon State University, Ontario, Oregon, Injury Barley control Treatment Rate Potato yieldt lb ai/acre cwt/acre Select + COC qt Select + COC qt Select + COC qt Select COC 1 qt Poast + COC qt Untreated LSD (0.05) NS NS NS Potatoes were harvested on September