Mark M. Claassen

Performance of wheat variety blends in Kansas

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Grain Sorghum Response to Simulated Drift from Glufosinate, Glyphosate, Imazethapyr, and Sethoxydim1

Field experiments were conducted at four locations in Kansas in 1999 and 2000 to evaluate grain sorghum response to simulated drift rates of four herbicides. Imazethapyr, glufosinate, glyphosate, and sethoxydim were applied at 1/3, 1/10, 1/33, and 1/100 of the use rate when plants were 10 to 20 cm tall. Visible crop injury increased as rates of each herbicide increased. Glyphosate and imazethapyr caused the most injury and glufosinate the least. Data show that some plants that were significantly injured 2 wk after treatment (WAT) recovered 8 WAT. However, some plants that received the highest rate of imazethapyr or glyphosate died. Grain sorghum yields were reduced only when injury was severe. This research showed that the potential for sorghum injury from off-target herbicide drift is greater from imazethapyr and glyphosate than from sethoxydim or glufosinate. Nomenclature: Glufosinate; glyphosate; imazethapyr; sethoxydim; sorghum, Sorghum bicolor (L.) Moench. Additional index words: Crop injury, herbicide drift, herbicide symptoms. Abbreviations: DAT, days after treatment; WAT, weeks after treatment.

Analysis of cold tolerance in sorghum under controlled environment conditions

Grain sorghum (Sorghum bicolor (L.) Moench) originated in the semi-arid tropics and is generally sensitive to low-temperature stress. Early planting and use of minimum tillage necessitate the development of sorghum hybrids with early season cold tolerance. Genetic variability for cold tolerance exists in sorghum and has been detected by early planting under field conditions and by analysis of seeds and plants under growth chamber conditions. There is limited information on the efficiency of evaluating cold tolerance under growth chamber conditions and the relationship with field performance. The objectives of this study were to quantify the variability of cold tolerance in commercial hybrid seed lots under growth chamber conditions, to exam different components of cold tolerance and their relationships, and to evaluate the consistency of lab test results with data from field tests. Thirty commercial hybrid seed lots were evaluated by growing the entries under 15/10, 13/10, 11/8, and 25/20 °C day/night temperature in a 13/11 h cycle in a growth chamber. Traits measured included emergence percentage, emergence index, shoot and root dry weight, seedling height, and vigor score. Significant genotypic differences were detected for all traits. Correlations among the traits were significant and favorable, which confirmed that simultaneous improvement of these traits should be possible. The same seed lots were also evaluated in a soil-free plate-based assay, in which percent germination, and shoot and root elongation of the seed lots grown in dark at 15 °C were measured. Results from both laboratory tests, soil-based and plate-based, were correlated with data collected in a field study, which was conducted to evaluate cold tolerance of commercial sorghum hybrids at Manhattan, Hesston, Bellville, and Garden City, KS in 1998 and 1999. Single-trait correlations between lab and field studies were significant. Differentiation based on rank-summation index of common traits, rank-summation index correlations and the overlap of best entries, further provided strong support of the efficiency of predicting and identifying elite hybrids using growth chamber assays.

Differential Response of Grain Sorghum Hybrids to Foliar-Applied Mesotrione

Abstract The selection of herbicide-resistant weeds in grain sorghum production has prompted researchers to explore alternative herbicides to prevent, delay, and manage herbicide-resistant weed biotypes. Greenhouse and field experiments were conducted to evaluate the differential response of sorghum hybrids to POST application of mesotrione. In a greenhouse experiment, 85 sorghum hybrids were treated with 0, 52, 105, 210, and 315 g ai/ha mesotrione when plants were at the three- to four-leaf collar stage. Sorghum response ranged from susceptible to tolerant sorghum hybrids. ‘Pioneer 84G62’, ‘Pioneer 85G01’, and ‘Triumph TR 438’ were the three most susceptible, whereas ‘Dekalb DKS35-70’, ‘Frontier F222E’, and ‘Asgrow Seneca’ were the three most tolerant hybrids. One week after treatment (WAT), the mesotrione rate causing 50% visible injury ranged from 121 to 184 and 64 to 91 g/ha in the most tolerant and susceptible hybrids, respectively. Mesotrione dose–response studies were conducted under field conditions on four sorghum hybrids. One WAT, injury symptoms were greater (up to 23%) in Pioneer 85G01 than in Asgrow Seneca (< 14%). However, all plants appeared normal by the end of the growing season. In addition, sorghum yields were not reduced by mesotrione treatments as verified by correlation coefficient analysis. Nomenclature: Mesotrione; sorghum, Sorghum bicolor (L.) Moench. SORBI

Seed Treatment Effects on Early-Season Pests of Corn and on Corn Growth and Yield in the Absence of Insect Pests

Abstract Second-generation neonicotinoid insecticides are being used to protect seeds and seedlings against injury by early season insects on a wide variety of crops. Seed-applied insecticides have recently been commercialized in the USA for early season insect control in corn. The systemic insecticides clothianidin (Poncho®) and thiamethoxam (Cruiser®) applied as seed treatments were evaluated for their effect on corn yield in the absence of noticeable insect attack over a three year period at a number of locations representing diverse growing environments in Kansas. No consistent effect on yield was detected for either compound at either high or low rates in locations where insects were not observed at damaging populations. Controlled-environment studies detected no differences in early season growth in the absence of insect pests in response to the same two rates of both insecticides. Both compounds were evaluated for their effect on early season corn pests and were found to be effective at high and low rates on wireworm, white grub, flea beetles and chinch bugs. Higher rates of both compounds were needed to reduce feeding damage caused by black cutworm. Seed treatments with either compound would be useful where early season pests are chronic problems.

Cotton Response to Simulated Drift of Seven Hormonal-Type Herbicides

Field experiments were conducted at Manhattan and Hesston, KS, in 2004, and at Manhattan, KS, in 2005, to evaluate cotton response to seven hormonal-type herbicides. Herbicides 2,4-D amine, 2,4-D ester, clopyralid, picloram, fluroxypyr, triclopyr, and dicamba were each applied at 0, 1/100, 1/200, 1/300, and 1/400 of the herbicide use rates on cotton in the six- to eight-leaf stage. Herbicide use rates were 210 and 280 g ae/ha for fluroxypyr and clopyralid and 561 g ae/ha, for 2,4-D amine, 2,4-D ester, dicamba, picloram, and triclopyr. At 14 d after treatment (DAT), all herbicides caused leaf cupping and epinasty, except triclopyr and clopyralid, which caused severe bleaching and chlorosis. The order of visual injury ratings was 2,4-D ester > 2,4-D amine > picloram > dicamba > fluroxypyr > triclopyr > clopyralid. By 56 DAT, slight injury symptoms were observed on plants treated with all herbicides, except all rates of 2,4-D, from which symptoms were severe. All rates of 2,4-D and the highest rate of picloram caused more than 60% flower abortion. Ranking of fiber yield reduction after herbicide treatment was 2,4-D ester > 2,4-D amine > picloram > fluroxypyr > dicamba > clopyralid > triclopyr. This research demonstrated that cotton is extremely susceptible to simulated drift rates of 2,4-D and picloram, whereas clopyralid and triclopyr caused early injury, with minimal effect on cotton yield. Nomenclature: Tribufos; S,S,S-tributyl phosphorotrithioate; cotton, Gossypium hirsutum L. ‘PM 2145 RR’.

Risk Analysis of Tillage and Crop Rotation Alternatives with Winter Wheat

The economic feasibility of soybeans, grain sorghum, and corn in annual rotation with winter wheat using reduced tillage and no-tillage systems in the Central Great Plains was evaluated, with continuous wheat and grain sorghum also analyzed. Net returns were calculated using simulated yield and price distributions based on historical yields, two historical annual price series, and 2011 costs. Stochastic Efficiency with Respect to a Function was used to determine the preferred strategies under various risk preferences. The no-till wheat-soybean and reduced-till wheatsoybean systems are the first and second most preferred, regardless of the level of risk aversion.

Pyroxsulam Compared with Competitive Standards for Efficacy in Winter Wheat

Abstract Field studies at six locations over 3 yr in Kansas compared pyroxsulam at two application timings to competitive standards for winter annual weed control in winter wheat. Pyroxsulam applied fall-POST (FP) controlled downy brome 84 to 99% and was similar to or greater than sulfosulfuron, propoxycarbazone, or propoxycarbazone plus mesosulfuron. Downy brome control was lower when application timing was delayed until spring (SP), such that no herbicide provided more than 90% downy brome control. Cheat control was 97% or more with almost all herbicides applied FP, and greater than 90% in most locations when herbicides were applied SP. Sulfosulfuron was the exception with only 30 to 81% cheat control. All FP-applied herbicides, except sulfosulfuron at Manhattan, KS, controlled blue mustard 95% or more. Pyroxsulam and propoxycarbazone plus mesosulfuron FP completely controlled henbit at Hesston, KS, in 2009, but no herbicide treatment provided more than 60% control when applied SP. Averaged over application timings, pyroxsulam provided the greatest henbit control (76 and 78%) at Manhattan and Hays, respectively, in 2009, and FP treatments were 33 and 28 percentage points more effective than SP treatments at those locations. Averaged over application timing, wheat yields did not differ between herbicide treatments in five of six locations. Averaged over herbicide treatment, FP-treated wheat yielded more grain than SP-treated wheat at three of the six locations. Nomenclature: Mesosulfuron; propoxycarbazone; pyroxsulam; sulfosulfuron; blue mustard, Chorispora tenella (Pallas) DC. COBTE; cheat, Bromus secalinus L. BROSE; downy brome, Bromus tectorum L. BROTE; henbit, Lamium amplexicaule L. LAMAM; common wheat, Triticum aestivum L.

Effect of postemergence mesotrione application timing on grain sorghum.

Abstract Field experiments were conducted at Belleville, Colby, Hays, Hesston, Garden City, and Manhattan, KS, to determine grain sorghum response to POST application of mesotrione at three application timings. Mesotrione was applied at 52, 105, 157, and 210 g ai/ha in combination with 280 g ai/ha atrazine to grain sorghum at heights of 5 to 8, 15 to 20, and 30 cm, which correspond to early POST (EPOST), mid-POST (MPOST), and late POST (LPOST), respectively. All mesotrione rates caused injury at all application timings. Overall, grain sorghum injury from mesotrione was greatest at 1 wk after treatment (WAT); plants partially recovered from injury by 4 WAT. Mesotrione applied EPOST injured grain sorghum more than when applied at MPOST and LPOST timings. The EPOST application injured grain sorghum 19 to 88%, whereas injury from MPOST and LPOST application was 1 to 66% and 0 to 69%, respectively, depending on rate. Mesotrione injury was least at Belleville and most at the Hesston and Garden City (irrigated) sites regardless of growth stage. Correlation coefficient analyses indicated that observed mesotrione injury symptoms were not well correlated with grain sorghum yield; thus, mesotrione injury to grain sorghum did not influence grain yield. However, initial grain sorghum injury was severe, and this will likely be a major concern to producers. Abstract Se condujeron experimentos de campo en Belleville, Colby, Hays, Hesston, Garden City y Manhattan, KS para determinar la respuesta de aplicaciones post-emergentes en sorgo de grano de mesotrione en 3 intervalos de aplicación. El mesotrione fue aplicado en dosis de 52, 105, 157 y 210 g ia/ha en combinación con 280 g ia/ha de atrazine en etapas de crecimiento de 5 a 8 cm., de 15 a 20 cm y de 30 cm, las cuales corresponden a la emergencia temprana (EPOST), emergencia media (MPOST) y emergencia tardía (LPOST) respectivamente. Todas las dosis de mesotrione causaron daño en todos los intervalos de aplicación. De todos los tratamientos el que mayor daño causó al sorgo de grano fue el de mesotrione aplicado una semana después del tratamiento (1 WAT), las plantas se recuperaron parcialmente de los daños a las 4 semanas después del tratamiento (4 WAT). La aplicación temprana de mesotrione (EPOST) causó más daño al sorgo que cuando fue aplicado en la emergencia media (MPOST) y la emergencia tardía. La aplicación temprana dañó el sorgo de un 19% a un 88% mientras que el daño en la emergencia media y emergencia tardía fue de un 1% a un 66% y de un 0 % a un 69% respectivamente, dependiendo de la dosis. El menor daño causado por mesotrione ocurrió en Belleville y el mayor en Hesston y Garden City, ambos sitios irrigados, independientemente de la etapa de crecimiento. El análisis del coeficiente de correlación indicó que los daños observados por la aplicación de mesotrione no fueron bien correlacionados con los rendimientos del sorgo, mientras que el daño de mesotrione no incluyó los rendimientos del grano. Sin embargo, el daño inicial fue severo, y esto será probablemente una preocupación importante para los productores de sorgo. Nomenclature: Mesotrione, sorghum, Sorghum bicolor (L.) Moench. ‘Pioneer 84G62’ SORBI

Are Bordered Plots Necessary for Corn Performance Tests

The range of heights and maturities present in a corn hybrid test has the potential to influence the relative importance of border rows, yet many breeding and performance testing programs use unbordered, two-row plots. A series of experiments was conducted at three sites in two years to evaluate the need for border rows in small-plot corn hybrid tests containing hybrids that differ in maturity and height. The six environments provided average grain yields of 77 to 227 bu/acre. Four corn hybrids provided contrasting combinations of relative maturity (RM) and height: 102 RM, medium-short; 110 RM, medium-short; 110 RM, medium-tall; and 116 RM, tall. Hybrids were planted in plots with four rows, 30 ft long, in a randomized complete block experimental design. The outer two rows of each plot functioned both as the border rows for the 4-row, bordered plot treatment and as the plot rows for the 2-row, unbordered plot treatment in a type of split-plot arrangement. Hybrid yield ranks did not change significantly in response to presence or absence of border rows in any of the six environments, supporting the conclusion that bordered plots are not necessary for accurate estimation of yield ranks in corn hybrid performance tests.