Sorghum Injury Research Articles

Grain Sorghum Response to Simulated Fomesafen and Terbacil Carryover from Watermelons in Georgia

Abstract Georgia growers can benefit from double-cropping grain sorghum following watermelon to maximize land use and add economic value to their operations. However, capitalizing on the economic advantages of harvesting two crops within a single season must account for potential herbicide injury to rotational crops. An integrated weed management strategy that includes a preplant application of fomesafen and terbacil is recommended for weed control in watermelon production systems. However, currently labeled plant-back restrictions for grain sorghum require a minimum of 10 and 24 months for fomesafen and terbacil, respectively. Therefore, this research aimed to determine the tolerance of grain sorghum to fomesafen and terbacil following soil applications applied 90 to 100 d before planting (DBP). Experiments were conducted at the University of Georgia Ponder Research Farm from 2019 to 2023. The experimental design was a randomized complete block with 4 replications. Five rates of fomesafen (35, 70, 140, 210, 280 g ai ha-1), four rates of terbacil (3.5, 7.0, 10.5, 14.0 g ai ha-1) and a non-treated control, were evaluated. In 2019, fomesafen caused significant sorghum leaf necrosis, plant density reductions, height reductions, and yield reductions of at least 16%, especially when applied at rates ≥ 210 g ai ha-1. Terbacil had little to no effect on sorghum injury, density, height, or yield in any year. These results suggest that sorghum has sufficient tolerance to terbacil when applied 90-100 DBP. In 4 of 5 years, sorghum had an acceptable tolerance to fomesafen when applied 90 to 100 DBP. However, yield losses observed in 2019 suggest that caution should be taken when fomesafen is applied 90 to 100 DBP grain sorghum at ≥ 210 g ai ha-1.

Applying unoccupied aerial systems to assess genetic gain from mass selection for tembotrione tolerance in sorghum (Sorghum bicolor)

AbstractThe post‐emergent herbicide options to control grasses in sorghum have historically been limited. Therefore, a mass selection program was implemented to increase the tolerance of sorghum to the broad‐spectrum herbicide tembotrione. The objectives of this study are to determine (i) which observation timing and vegetative indices are most effective in assessing sorghum injury to tembotrione using unoccupied aerial system imagery and (ii) if mass selection can be used to increase the tolerance of sorghum to tembotrione. Using an unoccupied aerial system, several vegetative indices, collected at either 14 or 21 days after tembotrione application, accurately measured sorghum injury. Over four cycles of selection, tembotrione tolerance increased in a linear and consistent manner. This demonstrates that mass selection can be used as a strategy for developing herbicide tolerance in crops. The modest, but steady genetic gain indicates both the quantitative nature of the trait and sufficient heritability to improve it. Given further development, tembotrione‐resistant sorghum hybrids could provide an effective means of post‐emergent weed control for a range of common weeds.

Influence of fluazifop timing and rate on johnsongrass (Sorghum halepense) control in ACCase-resistant grain sorghum (Sorghum bicolor)

Abstract Genetic similarities between johnsongrass and grain sorghum leave producers with limited herbicide options for postemergence johnsongrass control. TamArkTM grain sorghum with resistance to acetyl-CoA carboxylase-inhibiting herbicides was developed through a collaboration between the University of Arkansas System Division of Agriculture and Texas A&M AgriLife Research. Two field experiments were conducted in 2021 in two locations each: Keiser and Marianna, AR, or Fayetteville and Marianna, AR. The objective of the first was to determine the optimal rate and application timing of fluazifop-butyl for control of natural johnsongrass populations in a noncrop setting, and the objective of the second was to evaluate johnsongrass control and TamArkTM grain sorghum tolerance in response to fluazifop-butyl applied at different timings and rates based on crop growth stage. The highest levels of johnsongrass control occurred when sequential applications of fluazifop-butyl were utilized. All sequential treatments provided at least 80% johnsongrass control at any rate or application timing tested. A single application of fluazifop-butyl provided greater than 90% johnsongrass control when applied at 210 g ai ha−1 to johnsongrass with fewer than 6 leaves. Weed size played a role in achieving high levels of johnsongrass control. Greater than 90% control was achieved when johnsongrass had 6 leaves or fewer at the initial application for the sequential application treatments. A single application of fluazifop-butyl at 105 g ai ha−1 resulted in no more than 82% johnsongrass mortality at any application timing. TamArk™ grain sorghum injury did not exceed 6% at any application timing or rate. It was therefore considered to be safe even if the initial application was made before the 6-leaf crop stage. Because no unacceptable levels of injury were observed with TamArk™ grain sorghum for fluazifop-butyl, johnsongrass size at the time of application should be the most critical aspect for control with this herbicide.

FirstAct for Efficacy in ACCase-Tolerant Grain Sorghum

The objective of this study was to compare FirstAct with several tank mix partners for efficacy in herbicide-tolerant grain sorghum. FirstAct (quizalofop) alone or in tank mixtures controlled Johnsongrass 94% or more. However, tank mixing FirstAct with any broadleaf herbicide was generally antagonistic to Palmer amaranth control. Minor sorghum injury was 5% or less by four weeks after postemergence treatment. Sorghum yields increased with all postemergence treatments except with atrazine alone.

Evaluating Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae), Population Dynamics, Feeding Injury, and Grain Yield Among Commercial Sorghum Varieties in Alabama.

The sugarcane aphid, Melanaphis sacchari (Zehntner), emerged as a severe pest of sorghum, Sorghum bicolor (L.), in Texas and Louisiana in 2013 and currently threatens nearly all sorghum production in the United States. Proper management of populations is critical as sugarcane aphid has a high reproductive potential and can rapidly damage plants, resulting in extensive yield losses. The overall objective of this work was to investigate sugarcane aphid population dynamics, and subsequent sorghum injury and grain yield on commercially available grain sorghum varieties in Alabama. This research includes three-site years of data that show variation in plant injury, physiological maturity, and yields among varieties tested. Although performance of each variety was variable among locations, potentially due to abiotic factors, four varieties including DKS 37-07, 1G588, 1G855, and 83P17 exhibited characteristics consistent with resistance and corroborates reports of resistance from other states.

Using Quinclorac to Control Annual Grasses and Palmer Amaranth in Grain Sorghum (Sorghum bicolor L.)

Field studies were conducted during the 2015 and 2016 growing seasons in south-central Texas to determine control of Palmer amaranth and annual grasses along with grain sorghum tolerance to quinclorac alone and in various combinations when applied to weeds < 5 cm (EPOST) or 10 to 16 cm tall (LPOST). When evaluated late-season quinclorac alone at 0.43 kg ae ha-1 controlled broadleaf signalgrass 72% when applied EPOST and 91% when applied LPOST. Combinations of quinclorac with either atrazine, pyrasulfotole + bromoxynil, dicamba, or dimethenamid-P controlled Palmer amaranth 88 to 100% when applied EPOST or LPOST; however, broadleaf signalgrass control with these combination was better when applied LPOST (75 to 95%) compared with EPOST (37 to 72%) applications. Texas millet control with quinclorac was poor in both years and was never greater than 54%. Quinclorac plus either atrazine, pyrasulfotole + bromoxynil, dicamba, or atrazine + dimethenamid-P caused at least 20% sorghum injury at one of three locations. No yield reductions from the untreated check were noted in either year; however, in 2016 all treatments with the exception of quinclorac alone at 0.29 kg ha-1 applied EPOST, quinclorac + pyrasulfotole + bromoxynil applied LPOST, quinclorac + atrazine + pyrasulfotole + bromoxynil applied LPOST, and quinclorac + dicamba at either application timing produced yields that were greater than the untreated check.

Reducing Grain Sorghum (Sorghum bicolor L. Moench) Injury From Postemergence Application of Mesotrione With Dicamba

Weed management in grain sorghum is limited by the number of herbicide options. A two-year (2017-2018) field study was conducted at the Mississippi State University Delta Research and Extension Center, in Stoneville, MS to evaluate the response of grain sorghum to mesotrione application alone or when tank-mixed with dicamba at the two-leaf and four-leaf growth stage of sorghum. Mesotrione was applied at 0.07 and 0.105 kg ai ha-1 alone or was tank-mixed with dicamba at 0.28 kg ae ha-1. Significant injury to grain sorghum from all herbicide treatments was observed compared with the untreated check. Increase in mesotrione application rate increased injury to grain sorghum from 14 to 19% at two-leaf and from 10 to 24% at the four-leaf stage by 4 weeks after application (WAA) in 2017. Adding dicamba to mesotrione reduced grain sorghum injury in both years. At 4-leaf sorghum application stage, mesotrione applied at 0.07 kg ha-1 resulted in greater grain yield than all other herbicide treatments, except mesotrione (0.105 kg ha-1) + NIS in 2017. Our results indicate that adding dicamba to mesotrione safes grain sorghum from injury caused by mesotrione alone.

Sequential Pyroxasulfone Applications with Fluxofenim Reduce Sorghum Injury and Increase Weed Control

Core Ideas Selective control of weedy grasses is difficult in grain sorghum due to the presence of wild relatives. Pyroxasulfone provided greater weed control than S‐metolachlor but caused more crop injury. Sorghum protection from pyroxasulfone provided by fluxofenim was dependent on the environment. Split applications of pyroxasulfone equal to the highest single rate provided similar weed control. Controlling weeds selectively is a challenge when producing grain sorghum [Sorghum bicolor (L.) Moench]. Pyroxasulfone, a preemergence (PRE) herbicide, has demonstrated excellent grass and broadleaf control in maize (Zea mays L.) and soybean [Glycine max (L.) Merr]. However, pyroxasulfone is not labeled for grain sorghum because crop injury is a major limitation. Our first objective was to evaluate five herbicide safeners in the greenhouse to determine their ability to protect sorghum from pyroxasulfone. Growth data indicated seed‐applied fluxofenim provided the highest level of protection to emerging seedlings. A second objective was to evaluate fluxofenim for protecting sorghum from single and sequential pyroxasulfone applications in the field. A split‐plot in a randomized complete block design evaluated six pyroxasulfone (whole plot) and two fluxofenim treatments (subplot) in 2015 and 2016. A single PRE treatment of S‐metolachlor, an untreated‐weedy control, and weed‐free control were compared with pyroxasulfone to assess weed control, crop injury and stand count, and grain yield. Pyroxasulfone provided greater weed control than S‐metolachlor. However, as pyroxasulfone rates increased both weed control and crop injury increased, regardless of safener. In contrast, sequential pyroxasulfone applications (90/120 or 120/90 g ai ha−1) did not elicit as much crop injury or stand reductions as a single PRE application at the same total rate (210 g ai ha−1) and maintained weed control, which resulted in higher yields. Despite increased crop tolerance and yield with sequential relative to single pyroxasulfone applications, these findings indicate a more effective herbicide safener for pyroxasulfone in grain sorghum is required.

Palmer amaranth control and grain sorghum injury with pyrasulfotole plus bromoxynil and tank mixtures

Palmer amaranth control and grain sorghum injury with pyrasulfotole plus bromoxynil and tank mixtures

Palmer Amaranth (Amaranthus palmeri) Control and Grain Sorghum (Sorghum bicolor) Injury with Pyrasulfotole plus Bromoxynil and Tank Mixtures

Field studies were conducted in 2009 and 2010 to determine control of Palmer amaranth and crop injury resulting from a postemergence (POST) premix application of pyrasulfotole + bromoxynil and various tank‐mix partners. The objectives were to (i) determine the effects of different pyrasulfotole + bromoxynil rates and tank‐mix partners applied at early and mid‐POST (EPOST and MPOST) on Palmer amaranth control; (ii) evaluate weed control following application at different Palmer amaranth sizes; and (iii) assess sorghum injury and yield as affected by herbicides applied at the 4‐leaf, 10‐leaf, and boot stages. At both EPOST and MPOST, pyrasulfotole + bromoxynil + atrazine alone or mixed with 2,4‐D or dicamba consistently provided better Palmer amaranth control (>98% at EPOST and >90% at MPOST) than bromoxynil + atrazine (94% at EPOST and 58% at MPOST). At EPOST, control of Palmer amaranth by pyrasulfotole + bromoxynil alone varied with year, but the control was 100% at 42 days after treatment (DAT) when pyrasulfotole + bromoxynil was tank‐mixed with atrazine at 0.50 lb a.i./acre or dicamba at 0.20 lb a.i./acre. Pyrasulfotole + bromoxynil at more than 0.02 + 0.14 lb a.i./acre plus atrazine at 0.50 lb a.i./acre provided 100% control at 42 DAT when Palmer amaranth was less than 9 inches tall. In controlling 15‐ to 18‐inch‐tall Palmer amaranth, the efficacy of pyrasulfotole + bromoxynil + atrazine ranged from 83% to 99%. Pyrasulfotole + bromoxynil + atrazine resulted in up to 28% leaf burn at 3 DAT when applied to 4‐leaf sorghum, but plants completely recovered from the injury within 28 DAT. Addition of dicamba to pyrasulfotole + bromoxynil + atrazine tended to reduce sorghum injury. However, application of pyrasulfotole + bromoxynil + atrazine + dicamba at the boot stage reduced sorghum grain yields up to 37%.

Effect of Carrier Volume on Grain Sorghum Response to Simulated Drift of Nicosulfuron

Research was conducted in 2010 and 2012 to determine the effect of simulated drift of nicosulfuron on growth and yield of grain sorghum. Herbicide rates represented 25, 12.5, and 6.3% of the use rate of nicosulfuron at 52 g ai ha−1. Nicosulfuron was applied in a constant carrier volume of 224 L ha−1where herbicide concentration decreased with reduction in rate, and in carrier volumes of 56, 28, and 14 L ha−1proportional to the 25, 12.5, and 6.3% herbicide rates, respectively. In 2010, grain sorghum injury and yield were greater when nicosulfuron was applied in constant compared to proportional carrier volume. Grain sorghum injury and plant height reduction increased with increasing nicosulfuron rate when averaged across carrier volume both years. In 2012, there was a greater reduction in grain sorghum yield from nicosulfuron applied in proportional carrier volume. These data indicate that simulated drift of nicosulfuron onto conventional grain sorghum causes significant height and yield reduction even at the lowest herbicide rate tested, and the effect of carrier volume may be influenced by seasonal rainfall.

Grain sorghum response to saflufenacil applied preemergence

Field studies were conducted in 2008 and 2009 at three locations on the Texas Southern High Plains to evaluate grain sorghum response to saflufenacil alone or in combination with dimethenamid. Hybrids ‘Pioneer 85G01’ and ‘Dekalb 44-20’ were planted and saflufenacil at 0.5–0.70 kg ai ha−1 or saflufenacil + dimethenamid at 0.05 + 0.44 to 0.2 + 1.75 kg ai ha−1 was applied preemergence. Injury to sorghum increased with increasing rates at all locations. Saflufenacil + dimethenamid was less injurious than saflufenacil applied alone at similar rates. ‘Pioneer 85G01’ was more susceptible to herbicide injury than ‘Dekalb 44-20.’ Differences in soil texture and organic matter likely contributed to saflufenacil-induced injury across locations. Rainfall within 10 days after planting appeared to increase sorghum injury.

The effect of mesotrione applied with adjuvants on weed control efficacy and forage sorghum tolerance

Field experiments were conducted over 2 years to determine the influence of timing, rate, and method of application of mesotrione on weed control, forage sorghum injury, and fresh weight biomass. Sucrosorgo 506 sorghum was treated with 120 and 80 g ha^{-1} of mesotrione with petroleum oil (PO) or methylated seed oil (MSO) plus 28% N urea-ammonium nitrate liquid fertilizer (UAN). Mesotrione was applied once between the 4- and 6-leaf stages of sorghum or split and applied between the 2- and 3-leaf and the 6- and 7-leaf stages in 2 equal applications, with or without adjuvants. Mesotrione at 120 g ha^{-1} effectively controlled all weed species, except Geranium pusillum. At 80 g ha^{-1} it effectively controlled Chenopodium album, Polygonum convolvulus, and Polygonum aviculare, and at the 80 g ha^{-1} split application (40 + 40 g ha^{-1}) it effectively controlled P. convolvulus and P. aviculare. Both PO and MSO, added to the spray liquid containing mesotrione at 80 g ha^{-1}, made it possible to effectively eliminate weeds; a split application with PO effectively reduced the occurrence of C. album, Brassica napus, Thlaspi arvense, P. convolvulus, and P. aviculare, and application with MSO reduced the occurrence of C. album, P. convolvulus, and P. aviculare. Mesotrione at 120 and 80 g ha^{-1} as a single application and at an 80 g ha^{-1} split application did not cause injury to sorghum plants. The addition of PO or MSO adjuvant to 80 g ha^{-1} of mesotrione applied at a single rate caused slight injury to sorghum plants, which quickly recovered. No injury or slight symptoms were found after a few weeks on sorghum plants treated with a mesotrione at 80 g ha^{-1} split with PO and MSO. The addition of UAN to the spray mixture, apart from mesotrione and PO and MSO, inhibited growth and chlorosis on the leaves. The rate of 80 g of mesotrione with adjuvants is recommended for forage sorghum.

Response of Aryloxyphenoxypropionate-Resistant Grain Sorghum to Quizalofop at Various Rates and Application Timings

Conventional grain sorghum is highly susceptible to POST grass control herbicides. Development of aryloxyphenoxypropionate-resistant grain sorghum could provide additional opportunities for POST herbicide grass control in grain sorghum. Field experiments were conducted at Hays and Manhattan, KS, to determine the effect of quizalofop rate and crop growth stage on injury and yield of aryloxyphenoxypropionate-resistant grain sorghum. Quizalofop was applied at 62, 124, 186, and 248 g ai ha−1at sorghum heights of 8 to 10, 15 to 25, and 30 to 38 cm, which corresponded to early POST (EPOST), mid-POST (MPOST), and late POST (LPOST) application timings, respectively. Grain sorghum injury ranged from 0 to 68% at 1 wk after treatment (WAT); by 4 WAT, plants generally recovered from injury. The EPOST and MPOST applications caused 9 to 68% and 2 to 48% injury, respectively, whereas injury from LPOST was 0 to 16%, depending on rate. Crop injury from quizalofop was more prominent at rates higher than the proposed use rate in grain sorghum of 62 g ha−1. Grain yields were similar in treated and nontreated plots; applications of quizalofop at different timings did not reduce yield except when applied MPOST at the Manhattan site.

Efficacy of postemergence herbicides tankmixes in aryloxyphenoxypropionate-resistant grain sorghum

The development of aryloxyphenoxypropionate (APP)-resistant grain sorghum could provide additional opportunities for postemergence herbicide grass control in grain sorghum. Field experiments were conducted in Texas (Bushland, and Yoakum), Kansas (Dodge City, Garden City, Hays, Manhattan, Colby, Ottawa, and Tribune), and South Dakota (Highmore) to evaluate the efficacy of quizalofop tank mixes in APP-resistant grain sorghum. Quizalofop was applied alone or in combination with dicamba, 2,4-D, prosulfuron, 2,4-D + metsulfuron methyl, or halosulfuron methyl + dicamba. Herbicides were applied when sorghum was 12–50 cm in height. Overall weed control was greater when quizalofop was applied with other herbicides than when applied alone. At 2 and 4 weeks after treatment (WAT), large crabgrass [ Digitaria sanguinalis (L.) Scop.], giant foxtail ( Setaria faberi Herrm.), and green foxtail [ Setaria viridis (L.) Beauv.] control were greater than 90% when quizalofop was applied alone or in combination with dicamba, halosulfuron methyl + dicamba, or prosulfuron. Palmer amaranth ( Amaranthus palmeri S. Wats.), puncturevine ( Tribulus terrestris L.), and tumble pigweed ( Amaranthus albus L.) control were greater than 90% in all treatments except when quizalofop was applied alone. Herbicide treatments, except those that included 2,4-D, caused slight to no sorghum injury. Grain sorghum yield was greater for all herbicide treatments compared to the weedy check. This research showed that application of quizalofop in combination with broadleaf weed herbicides provided excellent weed control in sorghum.

Effect of Postemergence Mesotrione Application Timing on Grain Sorghum

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.

Atividade residual de (imazethapyr+imazapic) para sorgo granífero (Sorghum bicolor) semeado em rotação com o arroz irrigado

Este trabalho teve por objetivo avaliar a atividade residual da mistura formulada dos herbicidas (imazethapyr+imazapic), marca comercial Only, para a cultura do sorgo granífero, cv. BR 304, semeado em rotação, após um, dois e três anos com arroz irrigado, no sistema de produção Clearfield® (CL). Os experimentos foram conduzidos em campo, em área da Universidade Federal de Pelotas, município de Capão do Leão-RS. Considerou-se o arroz como a cultura principal, o azevém como cultura sucessora e o sorgo como substituinte do arroz no sistema de rotação. À exceção da primeira semeadura de arroz, em cada ano, todas as culturas foram conduzidas pelo sistema direto. O delineamento experimental foi o de blocos ao acaso, com quatro repetições. Os tratamentos foram arranjados em esquema fatorial, em que o fator A comparou resíduo em diferentes ambientes (anos de cultivo de arroz CL) e o B avaliou o efeito de doses sobre o residual dos herbicidas. O arroz semeado foi o cv. IRGA 422 CL, e os tratamentos herbicidas foram doses da mistura formulada de (imazethapyr+imazapic) a 0, (75+25), (112,5+37,5) e (150+50) g ha-1, acrescidos de Dash a 0,5% v/v. Os experimentos ou ambientes foram denominados de A1, A2 e A3, respectivamente para um, dois e três anos de cultivo de arroz irrigado pelo sistema CL. Como espécie indicadora da presença de resíduos dos herbicidas utilizou-se o sorgo granífero, cv. BR 304. As variáveisresposta consideradas foram: população e estatura média das plantas, rendimento biológico, peso de mil grãos e produtividade do sorgo. Quanto a estatura de plantas e peso de mil grãos, ocorreu interação entre os fatores ambiente e dose dos herbicidas; já para as demais variáveis verificou-se significância estatística somente para doses dos herbicidas. Concluise que o cultivo de arroz irrigado no sistema de produção CL deixa resíduos dos herbicidas (imazethapyr+imazapic) no solo, capazes de causar danos irrecuperáveis ao sorgo cultivado em safra subsequente ao arroz.

Preemergence Herbicide Efficacy and Phytotoxicity in Grain Sorghum

Field studies conducted from 2005 to 2007 in Kansas compared the effects of KIH-485 and flufenacet to acetochlor and s-metolachlor applied PRE in grain sorghum. All treatments were combined with 1.12 kg/ha of atrazine for broadleaf weed control. KIH-485 and flufenacet, each at one time (1×) and two times (2×) the labeled rates, controlled large crabgrass 55 to 76% in 2005 and 94% or more in 2006 and 2007. In 2005, all herbicides controlled shattercane less than 20%, and only KIH-485 at the 2× rate controlled shattercane more than 70% in 2006 and 2007. Averaged over herbicides, green foxtail was controlled 98% in 2005, 77% in 2006, and 79% in 2007. Most herbicides controlled foxtail 86% or more when averaged over experiments, however, s-metolachlor at 1×, flufenacet at either rate, or atrazine alone did not. Sorghum was not stunted with KIH-485 or flufenacet in two of seven experiments. However, sorghum growth was reduced 23 to 54% with the 2× rates of KIH-485, flufenacet, or acetochlor in four experiments. Compared to the weed free control, sorghum stand establishment was reduced 18% with the 2× rate of flufenacet at Colby in 2006. At Hays in 2005, stand reductions occurred with acetochlor or KIH-485 at the 2× rates and either rate of flufenacet. Averaged over experiments, grain yields were reduced 9 and 10% with KIH-485 and flufenacet at the 2× rates, respectively. Where precipitation was greatest during the 2 wk following herbicide application, weed control was the best with these herbicides, but sorghum injury was also greatest.

Weed control and grain sorghum tolerance to flumioxazin

Field studies were conducted from 2002 to 2004 to determine weed control and sorghum tolerance to flumioxazin. Flumioxazin at 0.07 and 0.11 kg ai/ha was applied 30, 21, 14, 7, and 0 days prior to sorghum planting. Flumioxazin at either dose provided excellent control of Amaranthus tuberculatus and Parthenium hysterophorus but provided variable control of Panicum texanum. No sorghum injury was noted with flumioxazin at any application timing. Reduction in sorghum yields were noted where annual grasses and broadleaved weeds were not effectively controlled.

Safening grain sorghum injury from metsulfuron with growth regulator herbicides

Abstract Field and greenhouse experiments were conducted to evaluate the efficacy and safening of metsulfuron applied with dicamba, 2,4-D, clopyralid, and fluroxypyr with and without nonionic surfactant. Greenhouse data showed that 2,4-D and dicamba, but not fluroxypyr, safened grain sorghum from metsulfuron injury. In the field study, grain sorghum injury from metsulfuron was decreased when tank mixed with 2,4-D or dicamba but not when tank mixed with clopyralid or fluroxypyr. Tank mixes of 2,4-D or dicamba with metsulfuron did not reduce ivyleaf morningglory or velvetleaf control. At 4 wk after treatment (WAT), ivyleaf morningglory was controlled 95, 84, 59, and 91%, and velvetleaf was controlled 88, 82, 78, and 95% when metsulfuron was tank mixed with 2,4-D, dicamba, clopyralid, and fluroxypyr, respectively. In a separate field study, differential grain sorghum hybrid responses to a tank mix of metsulfuron + 2,4-D was examined. In general, a tank mix of metsulfuron and 2,4-D caused visible injury to al...