Ronald F. Krausz

Winter Annual Weed Control with Fall-Applied Corn (Zea mays) Herbicides1

Field studies were conducted during the 2000 to 2001 growing seasons to evaluate winter annual weed control and crop tolerance with fall-applied herbicides in corn at Belleville, IL. Atrazine, simazine, and rimsulfuron plus thifensulfuron applied in the fall controlled mouseear chickweed, henbit, and Carolina foxtail 93% or greater at planting the following spring. Flumetsulam controlled mouseear chickweed and henbit 98 and 93%, respectively, at planting. Metribuzin controlled mouseear chickweed and henbit 100 and 97%, respectively. CGA-152005 controlled mouseear chickweed, henbit, and wild garlic 93 to 100%. CGA-152005 provided the greatest control of wild garlic, with control ranging from 94 to 100% at planting. CGA-152005 plus simazine controlled 99 to 100% of all winter annual weeds evaluated. Reducing winter annual weed vegetation did not increase soil temperatures at 5-cm depth in May. CGA-152005 caused discoloration and height reduction of corn. CGA-152005 at the highest rate (60 g ai/ha) reduced corn plant height by 7% and grain yield by 8%. Nomenclature: Atrazine; CGA-152005, 1-(4-methoxy-6-methyl-triazin-2-yl)-3-[[2-(3,3,3-trifluoropropyl)-phenylsulfonyl]]-urea; flumetsulam; metribuzin; rimsulfuron; simazine; thifensulfuron; Carolina foxtail, Alopercurus carolinianus Walt. #3 ALOCA; henbit, Lamium amplexicaule L. # LAMAM; mouseear chickweed, Cerastium vulgatum L. # CERVU; wild garlic, Allium vineale L. # ALLVI; corn, Zea mays (L.) ‘Pioneer 33G28 LL’. Additional index words: Discoloration, height reduction, preemergence. Abbreviations: DAP, days after planting; DAT, days after treatment; POST, postemergence.

Response of Glyphosate-Resistant Soybean (Glycine max) to Trimethylsulfonium and Isopropylamine Salts of Glyphosate1

Field studies were conducted from 1998 to 2000 to evaluate the effects of the trimethylsulfonium (Tms) salt of glyphosate on glyphosate-resistant soybean at Belleville, IL. Glyphosate-Tms and glyphosate-isopropylamine (Ipa) at 1,120, 1,680, 2,240, 3,360, and 4,480 g ai/ha were applied at the V4 and R1 growth stages of glyphosate-resistant soybean. Glyphosate-Tms and glyphosate-Ipa caused greater chlorosis when applied at the R1 growth stage when compared with the V4 growth stage, and chlorosis increased with rate. Chlorosis ranged from 0 to 20% depending on the year. In 1998, glyphosate-Ipa at 2,240 and 3,360 g/ha applied at the R1 growth stage caused 4 to 5% more chlorosis than glyphosate-Tms at the same rates. In addition to chlorosis, glyphosate-Tms caused bleaching (white speckling) of soybean leaves, with bleaching increasing as glyphosate-Tms rate increased. Glyphosate-Ipa caused no bleaching, regardless of rate. Glyphosate-Tms and -Ipa caused no visible height reduction at 14 and 28 d after treatment in any year. In 1998 and 1999, glyphosate-Tms and -Ipa, at the highest rate applied at the R1 growth stage, increased days to maturity of soybean. Despite the injury and delay in maturity caused by glyphosate-Tms and -Ipa, there was no difference in grain yield across years because of glyphosate salt, rate, or application timing. Nomenclature: Glyphosate; soybean, Glycine max (L.) Merr. ‘Pioneer 94B01 RR’. Additional index words: Herbicide injury, postemergence, transgenic soybean. Abbreviations: DAT, days after treatment; EPSPS, 5-enolpyruvylshikimate-3-phosphate synthase; Ipa, isopropylamine; Tms, trimethylsulfonium.

Influence of Weed Competition and Herbicides on Glyphosate-Resistant Soybean (Glycine max)1

Abstract: Field studies were conducted from 1997 to 1999 to evaluate the influence of weed competition and herbicides on glyphosate-resistant soybean at the Belleville Research Center at Belleville, IL. Season-long weed competition did not delay maturity or reduce soybean population. However, season-long weed competition reduced soybean height by 10% and grain yield by 68%. Competition from weeds 30 cm in height or less did not increase days to maturity or reduce plant population, height, or grain yield. Chlorimuron plus thifensulfuron caused 6% height reduction at 21 d after treatment. Despite the injury from herbicides, none increased days to maturity or reduced plant height, population, or grain yield of soybean. The soil-applied herbicides alachlor, imazaquin, and pendimethalin and the postemergence herbicides acifluorfen, bentazon, chlorimuron, imazethapyr, and thifensulfuron did not reduce yield of glyphosate-resistant soybean. Nomenclature: Acifluorfen; alachlor; bentazon; chlorimuron; glyphosate; imazaquin; imazethapyr; pendimethalin; thifensulfuron; soybean, Glycine max (L.) Merr. ‘Asgrow 4401 RR’. Additional index words: Herbicide injury, soil-applied herbicides, preemergence, postemergence. Abbreviations: DAT, days after treatment; POST, postemergence; PRE, preemergence; UAN, urea ammonium nitrate.

Sulfentrazone Enhances Weed Control of Glyphosate in Glyphosate-Resistant Soybean (Glycine max)

Field studies were conducted from 1998 to 2000 at Belleville, IL, to evaluate tolerance and weed control in glyphosate-resistant soybean with sulfentrazone application. Sulfentrazone alone caused 14 to 16% height reduction 14 d after treatment (DAT), and sulfentrazone plus chlorimuron caused 26% height reduction 14 DAT. Minimal height reduction (0 to 11%) was observed 56 DAT. Sulfentrazone alone controlled giant foxtail 97 to 100%, yellow nutsedge 96 to 98%, common waterhemp 97 to 98%, common cocklebur 91 to 94%, and ivyleaf morningglory 100%. Sulfentrazone alone controlled common ragweed 63 to 89% and giant ragweed 50 to 72%. Sulfentrazone plus chlorimuron or cloransulam increased control of common and giant ragweed to 95% or greater. Sulfentrazone followed by glyphosate increased control of yellow nutsedge, common waterhemp, and ivyleaf morningglory compared with a single application of glyphosate. Sequential applications of glyphosate controlled weeds 93 to 100%. Sulfentrazone plus chlorimuron or cloransulam postponed the application of glyphosate at the 10-cm weed height by 12 d. Despite the injury, sulfentrazone did not reduce grain yield. Inadequate giant ragweed control reduced grain yield by approximately 48%. Nomenclature: Chlorimuron; cloransulam; glyphosate; sulfentrazone; common cocklebur, Xanthium strumarium L. #3 XANST; common ragweed, Ambrosia artemisiifolia L. AMBEL; common waterhemp, Amaranthus rudis Sauer AMATA; giant foxtail, Setaria faberi Herrm. SETFA; giant ragweed, Ambrosia trifida L. AMBTR; ivyleaf morningglory, Ipomoea hederacea L. Jacq. IPOHE; yellow nutsedge, Cyperus esculentus L. CYPES; soybean, Glycine max L. Merr. ‘Pioneer 94B01 RR’. Additional index words: Herbicide injury, postemergence, preemergence, stand reduction. Abbreviations: DAT, days after treatment; fb, followed by; POST, postemergence; PRE, preemergence; WL, weeks later.

Control of Italian Ryegrass (Lolium multiflorum) in Winter Wheat

Field studies were established in 1999 and 2000 to evaluate Italian ryegrass, wheat, and double-crop soybean response to fall and spring postemergence applications of flucarbazone, sulfosulfuron, clodinafop, diclofop, and tralkoxydim applied alone and in combination with thifensulfuron + tribenuron to winter wheat. Fall-applied herbicides caused 5% or less wheat injury. Spring-applied herbicides caused 3 to 45% wheat injury, and the greatest injury occurred with the combination of flucarbazone with thifensulfuron + tribenuron in the spring of 2001. Spring-applied sulfosulfuron, tralkoxydim, diclofop, and clodinafop caused 3 to 6% and 16 to 26% wheat injury in 2000 and 2001, respectively. Herbicide injury to wheat did not reduce wheat grain yield compared with the hand-weeded treatment. Italian ryegrass competition in the nontreated plots reduced wheat yield by as much as 33% compared with herbicide-treated plots. Italian ryegrass control was 89 to 99% from clodinafop and diclofop and 78 to 97% from flucarbazone, with no differences because of application timing in either year of the study. Italian ryegrass control from sulfosulfuron and tralkoxydim was greater from the spring of 2000 applications (94 to 99%) compared with the fall of 1999 applications (65 to 88%). However, in 2001, application timing (fall vs. spring) for sulfosulfuron and tralkoxydim did not affect Italian ryegrass control. Thifensulfuron + tribenuron combined with tralkoxydim reduced control of Italian ryegrass control compared with tralkoxydim alone in both years of the study. Italian ryegrass control was not reduced when thifensulfuron + tribenuron was combined with sulfosulfuron, flucarbazone, diclofop, or clodinafop. Italian ryegrass was controlled effectively by the acetyl-CoA carboxylase–inhibiting herbicides diclofop, clodinafop, and tralkoxydim. However, control of Italian ryegrass with the acetolactate synthase–inhibiting herbicides flucarbazone and sulfosulfuron was inconsistent. Double-crop soybean after wheat did not have foliar symptoms or yield loss from fall- or spring-applied herbicides. Nomenclature: Clodinafop; diclofop; flucarbazone; sulfosulfuron; thifensulfuron; tralkoxydim; tribenuron; Italian ryegrass, Lolium multiflorum Lam., Marshall #3 LOLMU; soybean, Glycine max (L.) Merr, ‘BT369CR’; wheat, Triticum aestivum L., ‘Pioneer 25R26’. Additional index words: Application timing, herbicide carryover, tank mixtures. Abbreviations: ALS, acetolactate synthase (EC 4.1.3.18); DAT, days after treatment; POST, postemergence.

Influence of Tillage, Cover Crop, and Preemergence Herbicides on Weed Control and Pumpkin Yield

ABSTRACT Many Midwestern and Eastern U.S. jack-o-lantern pumpkin (Cucurbita pepo L.) growers are interested in using no-tillage production practices. However, improved weed management practices must be developed before no-tillage will be readily adopted for pumpkin production. A field study was conducted to determine effects of tillage, winter rye (Secale cereale L.), and preemergence herbicides on weed control and pumpkin yield. Grass and broadleaf weed control was greater in no-tillage compared to conventional tillage, and cover crop use in a no-tillage system further improved the level of weed control. Early- and late-season control of giant foxtail (Setaria faberi Herrm.), common cocklebur (Xanthium strumarium L.), redroot pigweed (Amaranthus retroflexus L.), and common waterhemp (A. rudis Sauer) were highly correlated (0.48 ≥ r ≤ 0.86, P ≤ 0.01) with pumpkin yield and fruit size. Although applying clomazone+ethalfluralin to winter rye residues improved broadleaf weed control compared with no herbicide, the level of control for all broadleaf species was unacceptable (∼86%) by 60 days after herbicide treatment (DAT), regardless of tillage treatment. However, addition of halosulfuron or imazamox to clomazone+ethafluralin generally improved redroot pigweed and common waterhemp control in no-tillage and conventional tillage compared with clomazone+ethafluralin alone; common cocklebur control was improved with addition of halosulfuron only to clomazone+ethafluralin. Although pumpkin fruit numbers in the weed-free control did not differ (P > 0.05) from tank mixtures of clomazone+ethalfluralin with halosulfuron or imazamox, reductions in pumpkin fruit size (30–35%) and yields (18–20%) were observed for these herbicide treatments compared with the weed-free control. This research indicates that cover crops, such as winter rye, can be successfully integrated in no-tillage pumpkin production systems along with herbicides to improve weed management.

Response of Double-Crop Glyphosate-Resistant Soybean (Glycine max) to Broadleaf Herbicides1

Abstract: Field studies were conducted from 1997 to 1999 to evaluate the influence of broadleaf herbicides on double-crop glyphosate-resistant soybean injury and yield at Belleville, IL. Diphenylether herbicides applied postemergence (POST) caused 10 to 48% necrosis 7 days after treatment (DAT). POST herbicides caused 0 to 8%, 8 to 37%, and 0 to 12% height reduction 7 DAT in 1997, 1998, and 1999, respectively. In most instances, diphenylether herbicides did not delay soybean maturity, whereas imazethapyr applied POST delayed soybean maturity in 1998 and 1999. Acifluorfen plus bentazon reduced soybean height at maturity in 1997 and 1998, whereas lactofen, imazethapyr, and imazamox reduced height only in 1998. Diphenylether herbicides did not reduce grain yield when compared to the no-herbicide hand-weeded treatment, but imazamox reduced yield by 18%. Furthermore, the soil herbicides applied preemergence and diphenylether herbicides applied POST did not reduce grain yield when compared to glyphosate alone. Nomenclature: Acifluorfen; bentazon; glyphosate; imazamox; imazethapyr; lactofen; soybean, Glycine max (L.) Merr. ‘Asgrow 3601 RR’, ‘Asgrow 4501 RR’, and ‘Bergmann-Taylor 369 CR’. Additional index words: Herbicide injury, preemergence, postemergence, CGA-248757, CGA-277476, cloransulam, flumiclorac, fomesafen, imazaquin, pendimethalin. Abbreviations: DAT, days after treatment; POST, postemergence; PRE, preemergence.

Application Timing Determines Giant Foxtail (Setaria faberi) and Barnyardgrass (Echinochloa crus-galli) Control in No-Till Corn (Zea mays)'

Abstract: Field studies were conducted from 1996 to 1998 to evaluate grass control in no-till corn (Zea mays) with herbicides applied early preplant (EPP), preemergence (PRE), and postemergence (POST) at the Belleville Research Center at Belleville, IL. Grass control was affected by application timing rather than herbicide. The herbicides applied PRE provided more consistent giant foxtail (Setaria faberi) and barnyardgrass (Echinochloa crus-galli) control (90 to 98%) than the same herbicides applied EPP (0 to 92%). There also was no difference in giant foxtail and barnyardgrass control between the emulsifiable concentrate (EC) formulation and microencapsulated (ME) formulation of acetochlor. Rimsulfuron plus thifensulfuron applied POST provided 90 to 97% control of giant foxtail and barnyardgrass. Metolachlor, EC-acetochlor, SAN 582H, and rimsulfuron plus thifensulfuron provided 85 to 92% control of yellow nutsedge (Cyperus esculentus) compared with 63 to 74% control for BAY FOE 5043 plus metribuzin and ME-acetochlor. Corn grain yield was greater with herbicides applied either PRE or POST than applied EPP. Grass control and grain yield were greater with herbicides applied either PRE or POST compared with EPP. Nomenclature: Acetochlor, 2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide; BAY FOE 5043 (proposed name, flufenacet), N-(4-fluorophenyl)-N-(1-methylethyl)-2-[[5-(trifluoromethyl)-1,3,4-thiadiazol-2-yl]oxy]acetamide; metolachlor, 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide; metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one; rimsulfuron, N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(ethylsulfonyl)-2-pyridinesulfonamide; SAN 582H (proposed name, dimethenamid), 2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl) acetamide; thifensulfuron, 3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl] amino]sulfonyl]-2-thiophenecarboxylic acid; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; giant foxtail, Setaria faberi Herrm. # SETFA; yellow nutsedge, Cyperus esculentus L. # CYPES; corn, Zea mays L. ‘Pioneer 3335’. Additional index words: Early preplant, preemergence, postemergence. Abbreviations: DAP, days after planting; EC, emulsifiable concentrate formulation; EPP, early preplant; ME, microencapsulated formulation; POST, postemergence; PRE, preemergence.

Deep soil carbon after 44 years of tillage and fertilizer management in southern Illinois compared to forest and restored prairie soils

No-till (NT) management can reduce soil erosion and increase soil carbon (C) in agricultural systems, but there is less certainty regarding deeper soil and how long-term tillage and fertilization practices compare to other land-use systems. The objective of this study was to quantify tillage and fertilizer management effects after 44 years (20 years in continuous corn [Zea mays L.] and 24 years in corn–soybean [Glycine max L.] rotation) on bulk density and soil C concentrations and stocks to a 1 m (3.3 ft) depth in a somewhat poorly drained Bethalto silt loam near Belleville, Illinois, and compare to nearby forest and restored prairie soils. Four tillage (moldboard plow, chisel tillage [ChT], alternate tillage, and NT) and five fertilizer (no fertilization control, nitrogen [N]-only, N + N-phosphorus-potassium [NPK] starter, NPK + NPKstarter, and NPK broadcast) treatments showed bulk density was lower in NT than moldboard plow treatments in 0 to 15 (0 to 6 in) and 25 to 50 cm (10 to 20 in) depths. Complete NPK treatments generally resulted in higher C stocks than N-only and control treatments from 0 to 25 cm (0 to 10 in), but no differences were detected from 25 to 100 cm (10 to 39 in) or 0 to 100 cm (0 to 39 in) due to fertilizer. No-till management increased C stocks compared to tillage treatments for 0 to 15 cm (0 to 6 in) and was greater than the ChT treatment for 0 to 100 cm (0 to 39 in). No-till/NPK maintained greater cumulative soil C stocks to 1 m than either undisturbed forest soils or restored prairie soils. Additionally, NT/NPK had the maximum soil C increase over time of 0.36 Mg C ha−1 y−1 (0.16 tn C ac−1 yr−1) for the top 15 cm (6 in) over 44 years.

Control of Volunteer Horseradish and Palmer Amaranth (Amaranthus palmeri) with Dicamba and Glyphosate

Management of volunteer horseradish is a challenge when it is grown in rotation with other crops, such as corn and soybean. Although volunteer horseradish may not cause yield loss, these plants serve as hosts for various soilborne pathogens that damage subsequent horseradish crops. In addition to volunteer horseradish, glyphosate-resistant Palmer amaranth is becoming difficult to control in southwestern Illinois, as a consequence of the plants ability to withstand glyphosate and drought, produce many seeds, and grow rapidly. Field studies were conducted to evaluate the effect of glyphosate and dicamba on volunteer horseradish and Palmer amaranth control in 2014 and 2015. Glyphosate alone (1,265 and 1,893 g ae ha-1) and glyphosate plus dicamba at the high rate (1,680 g ae ha-1) provided the greatest volunteer horseradish control, ranging from 81% to 89% and 90% to 93%, respectively. Measures of root biomass reduction followed similar trends. Glyphosate alone provided the greatest reduction in volunteer horseradish root viability (79% to 100%) but was similar in efficacy to applications of glyphosate plus dicamba in most comparisons. Efficacy of PRE-only applications on Palmer amaranth control ranged from 92% to 99% control in 2014 and 68% to 99% in 2015. However, PRE-only applications were often similar in efficacy to PRE followed by (fb) glyphosate plus dicamba applied POST. Treatments containing flumioxazin did not control Palmer amaranth as well as other treatments. POST applications alone were not effective in managing Palmer amaranth. Many of the PRE fb POST treatment options tested will improve resistance management over PRE-only treatments, provide control of Palmer amaranth, and allow horseradish to be planted the following spring. Nomenclature: Dicamba; flumioxazin; glyphosate; horseradish, Armoracia rusticana P.G. Gaertn., B. Mey. & Scherb. ARWLA; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; corn, Zea mays L.; soybean, Glycine max (L.) Merr.