Crop Research in Oregon's Treasure Valley 1980

Transcription

1 REPLACEMENT Crop Research in Oregon's Treasure Valley 1980 A Research Report The Malheur Experiment Station ( Special Report p2 June 1980 Agricultural Experiment Station) K.A) (bs, Oregon State University, Corvallis

2 CONTENTS Page WEED CONTROL RESEARCH REPORT Introduction and Summary An Evaluation of Herbicide Treatments for Weed Control, Crop Tolerance and Inducement to Neckrot (Botrytis sp.) Infection.. Herbicides Applied During the Fall for Weed Control in Spring- Seeded Onions 14 Diclofop and BAS 9052 OH Applied Singly and in Combination with.metribuzin as Postemergence Treatments for Weed Control in Three Varieties of Russet Potatoes 18 An Evaluation for Tolerance of Russet Burbank Variety of Potatoes to DCPA Applied as Single and Repeat Postemergence Treatments 23 Barnyardgrass Control in Sugar Beets 26 The Tolerance of Four Varieties of Corn to Three Rates of DCPA When the Corn was Planted at 0, 2, 4, and 6 Weeks After Herbicide Application 28 Tolerance of Sweet Corn, Peas, and Sugarbeets Planted in Soils Previously Treated with Ethalfluralin and Triflural in Two Consecutive Years 32 The Comparison of Wettable Powder and Flowable Formulations of Metribuzin for Annual Weed Control in Established Alfalfa. 38 Herbicide Extender Study 41 Herbicides Evaluated for Control of Broadleaf Weeds in Bluegrass Grown for Seed 46 CONTROL IN FURROW IRRIGATED MINT 49 Applied Treatments of Soil-Active Herbicides for Control of Winter and Summer Annual Weeds in Mint 51 Crop Tolerance to Herbicides Applied in the Spring to Dormant and Emerged Mint 54 Herbicide Evaluation for Weed Control and Tolerance to Peppermint When Applied in Early Spring 59 Evaluation of Postemergence Herbicide Treatments for Weed Control and Tolerance to Peppermint 62 Spearmint and Peppermint Tolerance to Paraquat 65

3 Page Comparison of Asulox and Basagran for Western Goldenrod Control in Mint 69 Tolerance of Peppermint to Basagran Applied to Different Rates and Stages of Mint Growth 72 ALFALFA VARIETY TRIAL 74 ONION VARIETY TESTING 78 POTATO VARIETY TESTING SUGAR BEET VARIETY TESTING RESULTS 89 EVALUATION OF WINTER FEED WHEATS AND BARLEYS FOR THE TREASURE VALLEY 96 HYBRID CORN PERFORMANCE TESTS 105 TILLAGE EVALUATION FOR POTATO PRODUCTION 113

4 CONTRIBUTORS I. James Burr is an Associate Professor and Malheur County Extension Agent at Ontario 2. Dwayne Buxton is a Professor of Agronomy and Superintendent of the Malheur Experiment Station at Ontario 3. Dwight Fisher is a Research Technician at the Malheur Experiment Station at Ontario 4. Mathias F. Kolding is a Senior Instructor in Agronomy at the Columbia Basin Agricultrual Research Center at Pendleton 5. Oris Rudd is a Professor and Malheur County Extension Agent at Ontario 6. Charles E. Stanger is an Associate Professor of Agronomy at the Malheur Experiment Station at Ontario 7. Roger Twombly is a Biological Aide at the Malheur Experiment Station at Ontario

5 WEED CONTROL RESEARCH REPORT Charles E. Stanger Introduction and Summary This annual report includes weed control research which was conducted during the 1979 crop year. Summary weather information is shown in Tables 1-3. In some cases, application of herbicide treatments were begun in the fall of 1978 for control of weeds in perennial crops and crops planted in the spring of The experiments were established and evaluated by Charles E. Stanger and assisted by Dwight Fisher and Roger Twombley. Herbicides that are applied in the fall and remain active to control weeds in spring-planted crops have advantages over spring-applied preplant incorporated treatments, when they can be incorporated in the fall during the time when most of the field preparation is done for early spring-planted crops. The main disadvantages from spring preplant incorporated treatments are loss of soil moisture, increased soil compaction, and added mechanical operations. Several herbicides were evaluated as fallapplied treatments for weed control in onions, sugarbeets, and potatoes. DCPA (Dacthal), bensulide (Prefar), and diclofop (Hoelon) persisted over winter and resulted in better weed control and crop selectivity than springapplied treatments. Cycloate (Roneet) is registered and used successfully as a fall application for weed control in sugarbeets. Ethofumesate (Nortron) and Hoelon are also effective as fall applications for weed control in sugarbeets, giving season-long control of most problem species of annual broadleaf and grassy weeds. Vernolate (Vernam) and EPTC (Eptam) have been evaluated as fall treatments for weed control in Russet Burbank potatoes. Vernam has persisted over winter but Eptam has not. Experiments are underway evaluating differ-

6 ent Extenders with Roneet, Vernam, and Eptam as fall applications for weed control in potatoes. Postemergence applied herbicides have been evaluated for annual broadleaf and grassy weed control in onions and potatoes. Oxadiazon continues to be effective on broadleaf weeds and selective in onions when applied at the flag, 1 and 2 leaf stage. Bromoxynil is effective on broadleaf weeds when applied at the 1 or 2 leaf stage of onion growth. It is not uncommon for bromoxynil to cause some chlorosis to the onion leaves but the yellowing has been short-lived with no detrimental effects on yield or quality. BAS 9052 OH resulted in excellent control of barnyardgrass when many of the plants were in the 2 tiller stage when treatments were applied. Hoelon gave good control of 1 and 2 leaf barnyardgrass but had much slower activity than BAS 9052 OH. Excellent broadleaf and grass control was obtained when BAS 9052 OH was combined with Ronstar. Glyphosate (Roundup) applied just prior to onion emergence has controlled weeds emerging ahead of the crop. Roundup is expected to be registered 24(c) for use in onions in Hoelon or BAS 9052 OH, in combination with metribuzin, gave good control of kachia, lambsquarters, pigweed, and barnyardgrass with good selectivity to Russet Burbank, Norgold, and Lemhi potato varieties when applied as early postemergence treatments. In summer-applied treatments, the active soil life of Eptam was increased with Stauffer's herbicide Extenders at the 6:1 and 6:3/4 ratios. The Extender did not lengthen the active soil life of Vernam, but Vernam with or without the Extender had a soil-active life about equal to Eptam + Extender or about 2 weeks longer than Eptam alone. Russet Burbank potatoes were tolerant to DCPA when applied over the top of potato foliage just before furrow closure. Occasionally, onion crops have to be abandoned because of inadequate stands. Most

7 of these onions have been treated with DCPA. Trials show that corn can be safely planted in soils treated with DCPA, with certain precautions. Field corn varieties were more tolerant than sweet corn varieties and tolerance for all varieties increased up to 6 weeks after the initial DCPA application with each 2-week delay in planting the corn. The corn plants that emerged through DCPA-treated soil grew and developed normal plants. Bromoxynil controlled essentially a 100 percent of annual sow thistle when applied in the fall to seedling thistle plants. About 85 percent of the mint grown in Malheur County of Oregon and southwest Idaho is irrigated in furrows. Fall applications of soil residual herbicides activated by winter and early spring snow and rain, have been effective in controlling winter and summer annual weeds in peppermint and spearmint. To accommodate fall applications, irrigation furrows are made in the fall prior to the time herbicides are applied. Terbacil (Sinbar) is the most widely used herbicide on mint. Napropamide (Devrinol) used in combination with Sinbar fall-applied, has given good season-long annual broadleaf and grass control. Devrinol was registered for use in Oregon during the fall and winter of 1978 under a Section 18 label. Research is being conducted to evaluate short and non-soil residual type herbicides for weed control in mint. These herbicides are being evaluated as dormant fall and spring applications and as non-dormant postemergence treatments. Results show that MCPB, 2,4-DB, and bromoxynil applied as single treatments to dormant spearmint and peppermint at rates up to and including 2.0 lb ai/a did not reduce yields. MCPB and bromoxynil did, however, cause yield reductions to spearmint and peppermint when applied as repeat treatments. Single applied treatments of these herbicides were 3

8 effective in controlling winter and summer annual broadleaf weeds when treated in the seedling stage of development. Diclofop (Hoelon) applied as a postemergence treatment at 1.5 lb/a in combination with bromoxynil at 1.0 lb/a controlled, barnyardgrass, green foxtail, and many species of summer annual broadleaf weeds. Asulox (asulam) effectively controlled seedling green foxtail as a postemergence treatment at 2.0 lb/a with excellent crop tolerance. Goal (oxyfluorfen) is very promising for control of broadleaf weeds applied as fall and early spring applications. Devrinol (napropamide), in combination with Goal, gave excellent annual grass and broadleaf weed control as fall and early spring applied treatments. Surflan (oryzalin) controlled summer grasses selectively in both spearmint and peppermint. Sencor (metribuzin), at rates effective for weed control, injured mint excessively. Fall applications for Devrinol and Sinbar (terbacil continued to be a very effective treatment for control of annual-broadleaf and grassy weeds in furrow-irrigated mint. Western goldenrod was more effectively controlled with Asulox than Basagran (bentazon) as postemergence-applied treatments. Basagran applied as late-season applications caused some leaf burning in peppermint but significant reductions in yield were not measured. Paraquat applied at 0.5 lb/a to both spearmint and peppermint in the 6-8 inch stage of growth significantly reduced hay and oil yields., Paraquat applied at the 1-2 and 3-4 inch growth stage did not reduce yields.

9 Table 1. Summary of temperature data for the crop year Recorded at Malheur Experiment Station near Ontario Oregon Month Monthly Mean Highest Date Lowest Date No. Times 90 or Above No. Times 32 or Below October November December January February March April May June July August September Table 2. Summary of precipitation data for the crop year Recorded at Malheur Experiment Station near Ontario, Oregon Month Total Greatest in 24 Hours Date No. Days.10 or More Long Time Average October November December January February March April May June July August September Total 10.02

10 Table 3. Daily precipitation record, crop year Malheur Experiment Station near Ontario, Oregon Recorded at Date Oct. Nov. Dec. Jan. Feb. Mar. April May June July Aug. Sept T T T T T 2 T T T T 3.06 T T T T.08 T T 6 T T.02 T.22 T 7 T T T T T T T T T T T T T 19 T.12 T T T T T 23 T.04 T T T.10 T.01 T 26 T T T T.01 T T.29 T T T T.54 Total

11 An Evaluation of Herbicide Treatments for Weed Control, Crop Tolerance and Inducement to Neckrot (Botrytis sp.) Infection This study was initiated in the spring of 1979 to determine if onions treated with herbicides are more susceptible to neckrot (Botrytis) infection. Some onion growers are inclined to believe that herbicides may be injuring onion leaf foliage, thus making it easier for infecting fungus spores to gain entrance into the plant. These early infecting spores can remain in a dormant condition in the plant to be activated when conditions are proper, usually after the onions have been put in storage. Herbicides included in the study were DCPA, ethofumesate, nitrofen (ec), oxadiazon, Bromoxynil, diclofop, and BAS 9052 OH. DCPA and ethofumesate were applied as postplant preemergence treatments. The other herbicides were applied as postemergence treatments when the onions were in either the 1 or 2 leaf stage of onion growth. Each herbicide was applied at the normal recommended rate for weed control and crop safety and at a higher rate to give a better reading on whether herbicides are affecting onion susceptibility to infection by the neckrot fungus. Ringmaker and Dai Maru cultivars of yellow sweet spanish onion were used in the study. Ringmaker is early maturing and usually keeps better in storage than Dai Maru, which is late maturing. The experimental trial was set up as a split plot with the main plots onion cultivars and the subplot herbicide treatments. The land at the experimental site was plowed, then disced in the fall of 1978 and left over winter. In the spring, the area was triple K'd, harrowed, and bedded on 22-inch centers. The onions were planted on April 13 and the postplant herbicides applied on April 16. On April 17, the trial was furrowed out and irrigated in every other row.

12 The postemergence treatments at the 1-leaf stage were applied on May 15, the 2-leaf applications on May 24 and 25. The onions were slow in emerging this year and did not have the growth vigor onions normally have. This was because of compacted soil conditions, resulting from heavy rains and some hail which occurred after planting, prior to onion emergence. Although the herbicide treatments were applied to onions in this condition, the onions did not show undue herbicide injury. The herbicide treatments were evaluated for weed control and crop injury on May 29 and June 10, after which the plots were hand-weeded and. kept nearly weed-free for the remainder of the growing season. The onions were lifted on September 4, topped, and put in wooden crates on September 11 and 12, then put in storage at the Parma Experiment Station on October 17. The onions remained in storage until January 8, at which time they were graded for bulb size, bulb quality, and the amount of neckrot determined. Results The onion stands were good in all plots with both varieties. Both onion cultivars had good tolerance to DCPA, nitrofen, oxadiazon, diclofop, and BAS 9052 OH, and showed no discoloration or foliar injury from these treatments (Tables 4-5). Onions emerged through ethofumesate at the 3.0 lb/a rate but began to show injury to onions in the 2-3 leaf stage. This effect was not noted with ethofumesate at the 2.0-lb rate. The injury symptoms associated with the 3-lb rate appeared on the leaves and caused the leaves to be shortened and in a stiff, upright position. The waxy cuticle layer appeared to be very thick and the leaves a dark green color. The new leaves as they emerged grew normal and the final bulb growth and development was not affected. Bromoxynil caused the leaves to droop and become somewhat chlorotic for about 10 days. 8

13 The incidence of neckrot was so low this year that treatment effects could not be measured (Table 6-7). The amount of neckrot ranged from a low of 0.2 to a high of 2.1 percent between plots, but this difference was not consistent between treatments. Certain years, the amount of neckrot that occurs in commercial lots can average percent. On occasion, some growers lose 80 percent or more of their onions to neckrot. The postemergence treatments all gave good control of pigweed (Amaranthus retroflexus) and lambsquarters (Chenopodium album), the only broadleaf species of weeds in the trial. Ethofumesate and DCPA gave fair broadleaf weed control but under commercial production would require a postemergence treatment to give satisfactory weed control. The grass population was extremely high in this trial and was only effectively controlled when diclofop or BAS 9052 OH was applied as a postemergence treatment. BAS 9052 OH was very impressive with its contact activity on barnyardgrass, controlling the larger plants in the early tillering stage of growth. Diclofop was most effective on barnyardgrass in the 1 and 2 leaf stage and most of the grass sprayed when tillering recovered. BAS 9052 OH gave generally better grass control as a single application than diclofop as a repeat treatment. It was evident, however, that diclofop was controlling at least 85 percent of the late-season grass by soil residual activity. This effect with diclofop has been noted with previous trials where it has been effective in controlling grass through the growing season. This study will be continued in 1980.

14 Table 4. Evaluation of herbicides in onion neckrot study. Evaluated May 29, 1979 Herbicides Rate lb a.i./a Time Applied Crop Tolerance Percent Weed Control b Lambsquarters Pigweed Barnyardgrass DCPA 9 PE DPCA 12 PE Nortron 2 PE Nortron 3 PE DCPA + Tok ec PE + Fl +2-1f DCPA + Ronstar PE + Fl + 2-1f DCPA + Brominal PE + Fl + 2-1f Nortron + Tok ec PE + Fl + 2-1f Nortron + Ronstar PE + Fl + 2-if Nortron + Brominal PE + Fl + 2-1f DCPA + Tok ec PE + 2-1f DCPA + Ronstar PE + 2-1f DCPA + Brominal PE + 2-1f Nortron + Tok ec PE + 2-1f Nortron + Ronstar PE + 2-1f Nortron + Brominal PE + 2-1f Tok + Hoelon ( ) 2 Fl + 2-1f Ronstar + Hoelon ( ) 2 Fl + 2-1f BAS 9052 OH Ronstar 1 1-1f Check a The repeat treatments of Ronstar and Tok ec in combination with Hoelon look good. The best and most impressive treatment is a single application of Ronstar + BAS 9052 OH. It really did an all-around job on large grass (1-3 tillers) and lambsquarters and pigweed, 4-8 inches tall with good onion tolerance. b E valuation scale: 0 = no effect, 100 = complete kill

15 Table 5 Percent weed control and onion tolerance to herbicides applied as preemergence and postemergence treatments Herbicides DCPA DCPA ethofumesate ethofumesate Rate lb a.i./a c DCPA + nitrofen DCPA + oxadiazon DCPA + bromoxynil ethofumesate nitrofen ethofumesate oxadiazon ethofumesate bromoxynil DCPA + nitrofen DCPA + oxadiazon DCPA + bromoxynil ethofumesate nitrofen 4 ethofumesate oxadiazon 1.25 ethofumesate bromoxynil 0.66 nitrofen + diclofop oxadiazon diclofop 1.5 oxadiazon BAS 9052 OH 1 Visual Evaluations a - Percent Control Crop Injury Pigweed Lambsquarters Barnyardgrass Applied R1 R2 R3 Avg R1 R2 R3 Avg R1 R2 R3 Avg R1 R2 R3 Avg PE PE PE PE PE + 1-1f + 2-1f PE + 1-if + 2-1f PE + 1-1f + 2-if PE + 1-1f + 2-1f PE + 1-1f + 2-1f PE + 1-1f + 2-1f PE + 2-1f PE + 2-1f PE + 2-1f PE + 2-1f PE + 2-1f PE + 2-1f f + 2-1f f + 2-1f f Control a Evaluation Scale: 0 = no effect, 100 = complete kill b Two applications at this rate c All nitrofen was emulsifiable concentrate formulation

16 Table 6. Average weight per onion bulb from two cultivars treated with several herbicides as preemergence and postemergence applications. Average Size Bulb by Weight for 2 Cultivarsa Rate R1 R2 R3 R4 Avg Herbicide lb a.i./a Applied DCPA 9 PE DCPA 12 PE ethofumesate 2 PE ethofumesate c 3 PE DCPA + nitrofen PE + 1-1f + 2-1f 0, DCPA + oxadiazon PE + 1-1f + 2-1f DCPA + bromoxynil PE + 1-1f + 2-1f ethofumesate + nitrofen PE + 1-1f + 2-if ethofumesate + oxadiazon PE + 1-1f + 2-1f ethofumesate + bromoxynil PE + 1-1f + 2-1f DCPA + nitrofen PE + 2-1f DCPA + oxadiazon PE + 2-1f DCPA + bromoxynil PE + 2-1f ethofumesate + nitrofen PE + 2-if ethofumesate + oxadiazon PE + 2-1f ethofumesate + bromoxynil PE + 2-1f nitrofen + diclofop b 1-1f + 2-1f oxadiazon + diclofop f + 2-1f , oxadiazon + BAS 9052 OH f Control Main plots - onion cultivars (1 and 2) LSD 05 significant between cultivars Subplots w/n main plots (herbicide treatments within a cultivar) LSD a Cultivar 1 = Ringmaker; cultivar 2 = Dai Maru b Two applications at this rate. c All nitrofen was emulsifiable concentrate formulation.

17 Table 7. Percent neckrot in two different onion cultivars treated with several herbicides as preemergence and postemergence applications. Herbicide DCPA DCPA ethofumesate ethofumesate DCPA + nitrofen DCPA + oxadiazon DCPA + bromoxynil ethofumesate + nitrofen ethofumesate + oxadiazon ethofumesate + bromoxynil DCPA + nitrofen DCPA + oxadiazon DCPA + bromoxynil ethofumesate + nitrofen ethofumesate + oxadiazon ethofumesate + bromoxynil nitrofen + diclofop oxadiazon + diclofop oxadiazon + BAS 9052 OH Control Avg LSD.05 Rate lb a.i./a Applied Percent Neckrot by Weight for 2 Cultivarsa R1 R2 R3 R4 Avg PE PE PE PE PE + 1-1f + 2-1f PE + 1-1f + 2-1f PE + 1-1f + 2-1f PE + 1-1f + 2-1f PE + 1-1f + 2-1f PE + 1-1f + 2-1f PE + 2-1f PE + 2-1f PE + 2-1f , PE + 2-1f PE + 2-1f PE + 2-1f b 1-1f + 2-1f f + 2-1f f NS NS NS NS NS NS NS NS a Cultivar 1 - Ringmaker; cultivar 2 = Dai Maru b Two applications at this rate. c All nitrofen was emulsifiable concentrate formulation.

18 Herbicides Applied During the Fall for Weed Control in Spring-Seeded Onions This trial was conducted to continue the evaluation of DCPA, ethofumesate, and bensulide for weed control and selectivity in springseeded onions. Each herbicide was applied at two different rates as broadcast and banded treatments on November 20, The broadcast treatments were incorporated shallowly (3-5 cm) with a rototiller, then bedded. The band treatments (30 cm wide) were applied during the bedding operation; thus, the herbicide was actually left as a layer located at the base of the bed. The beds were shaped in rows with hilling shovels, throwing enough soil to form a peak in the center of each row bed. The distance from the center of one bed to the center of each adjacent bed was approximately 56 cm. The beds were left over winter. On April 4 and 5, the beds were pulled down nearly level with a spiketooth harrow, leaving enough of the furrow to guide the tractor so the onion seed could be placed in the center of the bed. Victory variety of yellow sweet spanish type onions were seeded on April 6, The treatments were evaluated for weed control and crop tolerance on May 7. Following evaluation, the plots were weeded and kept free of weeds until harvested on September 14. Data collected at harvest included total bulb yield and yield of bulbs at various diameters, including 7.6 cm and larger, cm, and cm (Tables 8-9). 14

19 Results DCPA, bensulide and ethofumesate persisted over winter when applied in November with herbicide activity equal to spring applications. Onions were tolerant to DCPA and bensulide when applied as either a band or broadcast application. Onion yields were reduced with ethofumesate, even at the low rate (2.24 kg/ha). Ethofumesate caused malformed, thus abnormal, plants which first showed when the onions were in the 2-3 leaf stage. This effect carried over into the harvested bulbs which were reduced in size, spongy, and misshapen. Barnyardgrass control was good with all treatments but control was generally better with bensulide than either DCPA or ethofumesate. Grass control with bensulide exceeded 95 percent. Ethofumesate was more active on lambsquarters and pigweed than were either DCPA or bensulide and bensulide was slightly better than DCPA. Bensulide at the 6.73 kg/ha rate gave considerably better broadleaf weed control than the 4.49 kg/ha rate. These data support data collected from previous trials concluding that these herbicides will persist over winter when fall-applied to effectively control weeds in spring-planted onions. Soil active herbicides requiring mechanical incorporation, applied in the fall, are of special interest to onion growers in arid areas because they eliminate the need for spring incorporation by mechanical tillage which generally results in the loss of soil moisture needed for seed germination and seedling growth. This is of increased importance under furrow irrigation and where planting dates precede the availability of irrigation water by as much as 6 weeks. 15

20 Table 8. Fall-applied herbicides for weed control in spring-planted onions. Herbicides DCPA DCPA bensulide bensulide bensulide bensulide ethofumesate ethofumesate ethofumesate Rate kg a.i./a Application Banded Broadcast Banded Banded Broadcast Broadcast Banded Broadcast Banded Visual Evaluationsa Percent Weed Control Crop Tolerance Lambsquarters Pigweed Barnyardgrass R1 R2 R3 Avg R1 R2 R3 Avg R1 R2 R3 Avg R1 R2 R3 Avg Control a Evaluation Scale: 0 = no effect, 100 = complete kill Date of evaluation: May 7, 1979 Seeding Date: April 6, 1979 General Information Crop: Yellow sweet spanish onions (Victory VAr.) Plot size: 9 rows x 9.2 m Soil texture: silt loam Organic matter: 1.2% Irrigation: furrow Application Information Broadcast: double overlap 8003 TeeJet fan nozzles Banded: 8003E TeeJet fan nozzles, 1 per row Carrier:. Water, 375 L/h broadcast 126 L/h banded Air temperature: 4.4 C Soil temperature: 4.0 C Harvesting Lifted onions September 5 Topped onions September 13 Graded and weighed onions September 4

21 Table 9. Fall-applied herbicides for weed control in sprin g-seeded onions. Herbicide Rate kg ai/h Application Harvested Yield of Various Sized Onion Bulbs (kg/ha) cm cm.>_ 7.6 cm Total Yield R1 R2 R3 Avg R1 R2 R3 Avg R1 R2 R3 Avg R1 R2 R3 Avg DC PA 10.1 Banded DCPA 10.1 Broadcast bensulide 4.49 Banded bensulide 6.73 Banded bensulide 4.49 Broadcast bensulide 6.73 Broadcast ethofumesate 2.24 Banded ethofumesate 2.24 Broadcast ethofumesate 3.37 Banded Control Yield = numbers listed above times 100 equals yields expressed in kg/ha

22 Diclofop and BAS 9052 OH Applied Singly and in Combination with Metribuzin as Postemergence Treatments for Weed Control in Three Varieties of Russet Potatoes Procedure Russet Burbank, Norgold, and Lemhi cultivars of potatoes were planted on April 23 in rows spaced 36 inches apart. Immediately following planting, the planted rows were tilled and the furrows made deep enough so no further cultivations were needed to accommodate season-long furrow type irrigations. The first irrigation was applied on May 10. This irrigation was applied to germinate weed seeds for seedling emergence to occur when the potato vines were 4-6 inches tall. Larger vines can form a canopy and protect emerging weeds from postemergence-applied herbicides. The herbicide treatments were applied on May 26 as double overlap applications with a boom 1.82 meters long and 8003 TeeJet nozzles spaced 25.4 cm apart. The trial area was again irrigated on the second day following the herbicide treatments. The treatments were evaluated for percent weed control and crop tolerance by visual ratings on June 8, June 22, and September 17. All broadleaf weeds were removed from the diclofop plots by hand-weeding to eliminate a yield affect because of broadleaf weed competition. The potatoes were harvested on September 18 with a potato harvester. The total plot area was harvested to obtain total yield data. A random sample containing 50 lbs of potatoes was taken for grading to determine tuber size and quality. Three hills of a red variety 18

23 (Norland) was planted to separate potatoes in different treatments to accommodate mechanical harvesting. The experimental trial was designed as a split-plot with potato varieties being main plots and herbicide treatments as subplots. Each treatment was replicated 3 times and each plot was 2 rows wide and 9.14 m long. Results All three potato cultivars (Russet Burbank, Norgold and Lemhi) had good tolerance to all herbicide treatments (Table 10). A few leaf margins on some plants showed slight necrosis a few days after application, but the symptom was very short-lived. Potato yields were significantly different between cultivars, but this was due to cultivar performance to normal yield differences also occurred within a single cultivar between herbicide treatments, but in all cases, the lowest tuber yields and tuber size occurred in the control plots because of weed competition. Russet Burbank was the variety with the earliest and most dense foliage, thus most competitive with weeds and the least amount of difference in tuber yields between treated and control plots. Norgold had the greatest reduction in yield in the control plots compared to the treated plots because of higher weed populations due to reduced vine growth and early maturity. Early broadleaf weeds were easily removed from diclofop plots, but later emerging broadleaf weeds were not removed because of the physical damage that was being done to the potato vines from tromping through the plots. In an adjacent trial, where metribuzin was applied in combinations with diclofop and BAS 9052 OH, the broadleaf weeds were not removed by hand-weeding. Lemhi produced the highest yield of 10 oz. and over-sized tubers compared to other cultivars. The higher yields of 10 oz. tubers with Lemhi and Norgold cultivars were associated with the higher rates of herbicides. 19

24 This tends to demonstrate crop tolerance at the higher rates and also the need for better weed control in the cultivars that have less dense foliage. Combination treatments of metribuzin and BAS 9052 OH at rates of 0.56 and 1.12 kg/ha, respectively, resulted in essentially complete control of pigweed, lambsquarters, and barnyardgrass (Table 11). BAS 9052 OH and diclofop showed no activity on broadleaf weeds. BAS 9052 OH was more active on barnyardgrass than diclofop at half the rate. Metribuzin was effective in controlling pigweed and lambquarters, but did not adequately control barnyardgrass in these trials irrigated by furrow irrigaiton. Based on these data, it appears that use rates of diclofop and BAS 9052 OH in combination with metribuzin will be about 1.4 and 0.84, respectively, to obtain desirable weed control under furrow irrigation. 20

25 Table 10. Percent weed control, crop injury and harvested tuber yields from 3 potato cultivars treated with diclofop and diclofop-plus as postemergence treatments. Lemhi is a new cultivar that was evaluated as A Weeds emer g ed in Norgold plots on 9-17 evaluation because vines were dead.. Visual Ratings Harvested Yields Rate Crop Injury Barnyardgrass 6-10 US Total Herbicides Cultivars Kg ai/h <6 oz oz 210 oz No.2 Yield cwt/h cwt/h cwt/h cwt/h cwt/h diclofop Russet Burbank diclofop Russet Burbank diclofop Russet Burbank diclofop-plus Russet Burbank diclofop-plus Russet Burbank ry Control Russet Burbank Main Plot Means diclofop Norgold diclofop Norgold diclofop Norgold diclofop-plus Norgold diclofop-plus Norgold Control Norgold Main Plot Means diclofop Lemhi diclofop Lemhi diclofop Lemhi diclofop-plus Lemhi diclofop-plus Lemhi Control Lemhi Main Plot Means LSD.05 Main Plots NS 75 Sub Plots NS 65 Interaction (Subplots same mainplots) Interaction (Subplots different mainplots) CVa 19% 13% - 6.4% CVb 17% 20% 5.4%

26 Table 11. Percent weed control, crop injury and harvested tuber yields of Russet Burbank variety of potatoes treated with metribuzin, diclofop and BAS 9052'0H as postemergence treatments. Rate Herbicides Kg ai/ac metribuzin metribuzin + BAS 9052 OH metribuzin + N.) BAS 9052 OH IN) metribuzin + diclofop metribuzin + diclofop Control LSD.05 CV (%) Visual Ratings Barnyard Harvested Yields Crop Injury Pigweed Lambsquarters Grass 6-10 US Total c6 oz oz.10 oz 2's Yield cwt/h cwt/h cwt/h cwt/h cwt/h NS 36 NS NS NS General Information: Fertilizer- 100 lbs P205 and 200 lbs N Irrigation- furrow Soil: Texture- silt loam ph- 7.3 OM- 1.2% Plot size: subplots 9.1 m long x 2 rows wide Replications: 3 Planting date: April 13 Seed spacing: 22.8 cm Row spacing: 0.91 m Skies- clear Air temperature- 24 C Soil temperature- 20 C Wind- calm Herbicide Application Information: Date of application- May 6 with bicycle wheel plot sprayer as doubleoverlap application. Nozzles teejet fan at 25.4 cm spacing on boom Pressure- 40 psi Carrier- water at 378 L/h Plant size when treatments were applied: a- potatoes 1. Russet Burbank 15 cm 2. Norgold cm 3. Lemhi 5-15 cm b- barnyard grass- 1 to 3 leaves c- pigweed- 2 leaves d- lambsquarters- 2 to 6 leaves

27 An Evaluation for Tolerance of Russet Burbank Variety of Potatoes to DCPA Applied as Single and Repeat Postemergence Treatments Introduction Dodder (cuscuta campestris) is a problem normally associated with the production of legume crops grown for seed production in the Treasure Valley area of eastern Oregon and southwest Idaho. As a result of dodder infestations in legume seed fields, this parasitic weed has become a problem to other crops grown in rotation with seed crops. Potatoes are a host crop to dodder, and potato yields and quality can be adversely affected by dodder infestations. Early emerging dodder can completely desroy potato foliage several weeks before harvest and under these conditions, heavy yield reductions can be expected. Although DCPA is registered for weed control in potatoes, it is not registered as a postemergence application under furrow irrigation nor for the control of dodder. Field observations have shown DCPA to be an effective treatment for dodder control when applied as a postemergence treatment prior to time of row closure by potato foliage. In order to secure a permit for commercial application of DCPA, it has to be evaluated for potato tolerance and possible residues in the harvested tubers. This study was initiated to obtain information on the tolerance of Russet Burbank variety of potatoes to DCPA at rates of 7.5 and 10.5 a.i./a applied to potato foliage as single and repeat applications and to analyze harvested tubers for possible residues of DCPA. 23

28 Experimental Procedures Russet Burbank variety of potatoes was planted on April 26 in a silt loam textured soil with 1.3% organic matter and a ph of 7.2 Cultural practices normally used to grow commercial potatoes under furrow irrigation *reused in growing the potatoes in this study. This includes fall land preparation (bedding), spring preplant sidedressing of temik and dasanit, and sidedressing of nitrogen after potato emergence. Herbicides other than the application of DCPA as experimental treatments, included vernolate fall-applied at the rate of 5 lb a.i./a and incorporated with a double disc before the field was bedded. The seed pieces were planted at approximately 9-inch spacing in rows spaced 36 inches apart. Each plot was 2 rows wide and 30 feet long. Each treatment was replicated three times in a complete randomized block experimental design. The first herbicide applications (single applications and first application of the repeat treatments) were applied on June 14, between the hours of 7:00 and 8:30 a.m. The potato foliage ranged in height from 12 to 16 inches. The second applications were applied on June 22, also between the hours of 7:00 and 8:00 a.m. The potatoes were making rapid growth and only a few inches separated foliage from adjacent rows. The material for each plot was mixed with 1 qt of water and applied with a CO 2 plot sprayer. The treatments were applied as broadcast applications over the top of the potato foliage. Spray pressure was 35 psi and nozzles used were TeeJet fan nozzles, size

29 The potatoes were harvested in early October. Data collected included yields of tubers less than 6 oz, 6-10 oz, 10 oz and larger, and for malformed culls. The tubers were graded for size automatically by a Kerian vegetable sizer. Samples of tubers were collected for analysis of possible DCPA residues. Results The foliage of the treated potatoes was observed for several days after the DCPA treatments were applied. At no time was any injury symptom noted. The foliage remained green and continued growth was normal. Yield differences between DCPA treatments and the untreated control for yields in the different size category or total yields did not exist. (Table 12). Yield and quality of the potato tubers were exceptionally good in this trial. The field was free of weeds, thus weed control ratings for DCPA efficacy could not be taken. Table 12. Tuber yields from Russet Burbank potatoes treated with DCPA applied as foliar treatments. Herbicides Rate a.i./a No. a Applications Less 6 oz Tuber 6-10 oz, Yields (cwt/a)b 10 oz And Larger Malformed Tubers Total DCPA DCPA DCPA DCPA Control LS NS NS NS NS NS.05 a For the repeat treatments, DCPA was applied at the rate of 7.5 or 10.5 each application. b Area harvested and tubers graded to determine yields were from 2 rows 30 feet long for 3 replications. 25

30 Barnyardgrass Control in Sugar Beets BAS 9052 OH and diclofop methyl (Hoelon) were evaluated for control of barnyardgrass and selectivity to sugar beets when applied as postemergence treatments. The treatments were applied as double-overlap broadcast applications with a bicycle-wheel plot sprayer equipped with 8003 TeeJet nozzles, spaced 25.4 cm apart, on a boom 2.23 m long. The sugar beets averaged 4 true leaves and the grass plants ranged in size from 1 leaf to 3 leaves when the treatments were applied. Result BAS 9052 OH was more active than Hoelon, resulting in both quicker and more complete control. This effect was particularly noticeable on the larger grass plants. Both materials showed good selectivity to the sugar beets ( Table 13). Neither material showed any activity on lambsquarters, kochia, redroot pigweed, or buckwheat weed species which were present in the plots. 26

31 Table 13. Barnyardgrass control in sugar beets. Visual Evaluationsa Rate Crop Tolerance Grass Control Treatments kg a.i./ha R1 R2 R3 Avg R1 R2 R3 Avg BAS 9052 OH BAS 9052 OH diclofop methyl diclofop methyl Control a Evaluation Scale: 0 = no effect, 100 = complete kill. Date of Evaluation: May 30, 1979 Seeding Date: April 5, 1979 Application Data Date: May 15, :00 a.m. Conditions: postemergence Air temperature - 8 C Soil temperature - 7 C Humidity - 45% % Cloud cover - 25% Wind speed - calm Method of Application Broadcast Carrier volume L/h Nozzle size flat fan Pressure - 2.8/cm2 Stage of plant growth when treatments applied: Sugar beets - 4 true leaves Barnyardgrass leaves Plot size: 4 rows wide x 9.14 m long Soil texture: silt loam Soil organic matter: 1.2% Soil ph:

32 The Tolerance of Four Varieties of Corn to Three Rates of DCPA When the Corn was Planted at 0, 2, 4, and 6 Weeks After Herbicide Application Introduction Nearly all the onions planted in the Treasure Valley area of eastern Oregon and southwest Idaho are treated with DCPA as a postplant preemergence treatment. Occasionally, because of inadequate onion stands, fields are abandoned to onion production and another crop is planted. Corn is a crop that most growers would like to plant.when onion stands are inadequate. It has been observed that some years corn has successfully followed onions when onions were treated with DCPA the current season prior to planting corn. This experiment was designed to determine if corn can be safely planted in soil previously treated with DCPA. Experimental variables in the study included three rates of DCPA (6, 9, and 12 lb a.i./a), for varieties of corn (Golden Jubilee, Style Pak, Crk 5440, and Crk 5440A) and four planting dates following the original application of DCPA (0, 2, 4, and 6 weeks). Experimental Procedures The trial was established in a silt loam textured soil with an organic matter content of 1.1%. The site was fall-plowed, then left until spring. In the spring, the site area was tilled and bedded. The beds were pulled down to nearly flat and DCPA applied on April 16, and shallowly incorporated on April 17 with a spike-tooth harrow. The experimental design was a split-split-plot randomized in a block. The 28

33 main plots were herbicide rates, the subplots were planting dates, and the sub-subplots were corn varieties. The sub-subplots were two rows wide and 22 feet long. Each treatment was replicated four times. The herbicides were applied as double-overlap applications with a bicycle-wheel plot sprayer. The spray pressure was 40 psi and nozzles were fan type TeeJet, size Water was the herbicide carrier and applied at the rate of 40 gallons per acre. The corn varieties included sweet corn (Golden Jubilee and Style Pak) and field corn (Crk 5440 and Crk 5440A). Planting dates were April 17, May 1 and 15, and June 2. The corn seed was pre-packaged with 90 seeds per packet, which seeded a single row 25 feet long. The corn was planted with a 4-row cone seeder equipped with double disc openers, planting the seed to a depth of 2 inches. The trial area was irrigated after each planting by furrow irrigation to assure adequate soil moisture for seed germination and seedling emergence. Weeds emerging in the plots not yet planted were controlled with Roundup applied at the rate of 2 lbs a.i./a. The treatments were observed at time of emergence for plant injury and compared for variations in stages of development that might be due to DCPA treatments. During the second week in July, plant counts were taken. The total number of normal plants existing in 2 rows of the sub subplots was counted and recorded to determine DCPA phytotoxicity. Results and Discussion Final stands for each variety of corn were affected as a result of planting date, DCPA rates, and natural differences between varieties because of genetic inheritance (Table 14). Final plant counts between the tw 29

34 field corn varieties (Crk 5440 and Crk 5440A) were about equal, regardless of treatment effects, but final stands differed significantl y between the sweet corn varieties. Golden Jubilee was superior to Style Pak in vigor throughout the test period and was less affected by planting dates and rates of DCPA. Stand counts for each corn variety increased significantl y within each DCPA treatment with each 2-week delay in planting date. This indicates that either DCPA was being rapidly degraded in the soil or that vigor, thus tolerance of corn varieties, increases as temperatures became more desirable for corn germination and growth. Observations during the time of corn emergence and seedling development indicate that nearly all (95% or better) the corn that emerges through DCPA treated soil will develop into normal plants. Normal plant development occurred with seedlings which showed some growth distortions, leaf chiorosis and varied amounts of necrosis on the first leaves. Differences in dates of maturity did not occur within corn varieties because of DCPA treatments. Based on the results of this study, it appears that both sweet and field corn varieties can be planted in soils previously treated with DCPA. It is recommended, however, that planting dates for corn be delayed for as long as possible after DCPA applications and that the soil be tilled shallowly in preparing the seedbed for corn planting. Since nearly all plants that emerge continue to develop normally, the chances for higher percent emergence would be increased with slightly higher seedling rates. This would be of particular importance when planting sweet corn varieties. 30

35 Table 14. Effect of DCPA and plantinc date on total number of plots for each variety of corn. Herbicide Planting Date Golden Style Jubilee Pak Varieties Crk 5440 Crk 5440A Herbicide Means DCPA (6 lbs) Avg 106 e Avg 87e Avg 124 e Avg Me 111.4a DCPA (9 lbs) Avg 98 e Avg 77e Avg 118 e Avg 126e 104.5a DCPA (12 lbs) Avg 97 e Avg 69e Avg 117 e Avg 125e a Control Avg 122e Avg 103e Avg T-3-1-e Avg 134e 122.8a Planting Date Planting Date x Variety Means Average d d d d b 87.0d d d d b A 132.2A 108.6, 109.5'92.5' 123.2' 1.' ' '111.2' 132.8' 140.5' 127.6b c 122.7c c-- a Main plot LSD 05 herbicides = 7.13 b Subplot LSD 05 planting date = 4.5 Sub-subplot LSDvarieties 05 = 3.7 Interaction - LSDPlanting Date x Varieties = 7.5 d comparison of.05 values across table comparison of values down table. Interaction - LSDHerbicides x Varieties = 7. 5 e comparisons of values.05 across table e comparison of values down table. 31