Crop Oil Concentrate Research Articles

Efficacy of dicamba and dicamba/tembotrione with and without ammonium sulfate for broadleaf weed control

Abstract Mixing ammonium sulfate (AMS) can increase dicamba volatility. Therefore, AMS cannot be used with dicamba products in dicamba-resistant soybean. However, most dicamba products applied in corn are labeled to mix with AMS. The objectives of this study were to evaluate broadleaf weed control with dicamba (DiFlexx®) and dicamba/tembotrione (DiFlexx® DUO) applied alone or with AMS or AMS substitute and their effect on broadleaf weed density and biomass. Field experiments were conducted in Illinois, Missouri, and Nebraska in 2018 and 2019. In Illinois and Nebraska, mixing AMS + crop oil concentrate (COC) with dicamba applied at 1,120 g ae ha−1 increased the control of Palmer amaranth and waterhemp (Amaranthus species) from 78% to 92% and velvetleaf from 73% to 96% compared with dicamba applied alone 14 d after application (DAA); however, Missouri data showed no difference. Mixing AMS + COC with dicamba/tembotrione at 597 and 746 g ai ha−1 did not improve broadleaf weed control 14 DAA at any site compared with dicamba/tembotrione applied alone. Control of Amaranthus species was increased from 82% with dicamba applied at 840 g ae ha−1 to 96% when mixed with AMS + COC 28 DAA in Illinois; however, control was similar to dicamba applied at 1,120 g ae ha−1. Broadleaf weed control did not differ among dicamba or dicamba/tembotrione 28 and 56 DAA in Missouri and Nebraska. Broadleaf weed density decreased from 64 plants m−2 to 24 plants m−2 with dicamba at 1,120 g ae ha−1 with AMS + COC 14 DAA in Nebraska; however, no differences were observed in broadleaf weed density or biomass 56 DAA in any state. The results suggest that dicamba or dicamba/tembotrione can be applied without AMS or AMS substitute, especially at higher rates, without losing broadleaf weed control efficacy.

Assessing the toxicity of selected pesticides to Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) pupae as a first step in the development of a potential novel deployment programme

ABSTRACT Trichogramma spp. have been used or have been proposed for use in biological control programmes of lepidopteran pests, including the European corn borer, Ostrinia nubilalis, the cotton bollworm, Helicoverpa armigera, and the spruce budworm, Choristoneura fumiferana. Releases are typically made by placing cards with parasitised eggs at set points in the field. However, this method can be cost-prohibitive due to its laborious nature. As a result, labour-saving mechanised release programmes have been developed, including distribution by spray equipment. However, few have investigated applying Trichogramma with a standard pesticide application (i.e. ‘tank mix’). As a first step to ascertain the feasibility of such a system, we observed the effect of immersion of T. ostriniae pupae in field-relevant concentrations of eight herbicides (bentazon, clethodim, fomesafen, quizalofop, Glacial acetic acid, glyphosate, imazamox, imazethapyr), three fungicides (Copper Hydroxide, flutriafol, and penthiopyrad), one insecticide (K+ salt of fatty acid), and five adjuvants (Ammonium Sulfate, Crop Oil Concentrate, Methylated seed oil, Non-ionic surfactant, and Urea-Ammonium Nitrate) on the emergence of T. ostriniae adults. The herbicides GAA and clethodim; the fungicides copper hydroxide, flutriafol, and penthiopyrad; and the adjuvants COC, MSO, and NIS all reduced T. ostriniae emergence compared to a water control. No emergence was observed with exposure to quizalofop, GAA, or K+ salt of fatty acid treatments. Other treatments did not affect emergence compared to water. Thus, deploying Trichogramma with a standard pesticide application may be a feasible labour-saving distribution method that warrants further investigation.

Influence of 2,4-D, dicamba, and glyphosate on clethodim efficacy of volunteer glyphosate-resistant corn

AbstractManagement of volunteer glyphosate-resistant (GR) corn may be problematic in soybean resistant to glyphosate and 2,4-D or dicamba, as auxinic herbicides often antagonize graminicide efficacy. Field and greenhouse trials were conducted using mixtures of 2,4-D or dicamba in combination with glyphosate and clethodim-A (formulated without an adjuvant) or clethodim-SM (adjuvant-inclusive formulation) to determine the effect on volunteer GR corn control. Neither auxinic herbicide reduced clethodim efficacy, regardless of clethodim rate or formulation in field trials. However, the addition of glyphosate to these mixtures at the 35 g ai ha−1 clethodim dose reduced control from clethodim-A and clethodim-SM by 62% to 75% and 27% to 47%, respectively. Increasing the clethodim dose to 105 g ha−1 or greater in combination with glyphosate and either auxinic herbicide generally restored clethodim efficacy (74% to 98% control); in one site-year, the addition of glyphosate plus dicamba to clethodim-A at 140 g ha−1 still reduced control by 34%. In greenhouse experiments, clethodim-A efficacy was reduced by 17% and 28% when applied with glyphosate plus 420 and 1,680 g ae ha−1 2,4-D, respectively, in the absence of crop oil concentrate (COC). Increasing the dose of dicamba in a similar mixture had a negligible effect. Irrespective of auxinic herbicide dose, the inclusion of COC to clethodim-A mixtures with glyphosate plus 2,4-D or dicamba resulted in ≥ 90% control. These results specify an enhanced risk of reduced clethodim efficacy on volunteer GR corn when glyphosate is added to mixtures containing 2,4-D or dicamba. To optimize control from these mixtures, clethodim should be applied at ≥ 105 g ha−1 and should include an activator adjuvant in the form of COC and/or an adjuvant-inclusive clethodim formulation. This recommendation contrasts with several labels of clethodim that do not require COC when applied with adjuvant-loaded glyphosate products.

Do adjuvants reduce the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na?

AbstractAcetyl co-enzyme A carboxylase (ACCase)-resistant rice allows quizlaofop-p-ethyl to be applied as a POST control of troublesome grass weeds. A field study was conducted in 2017 and 2018 at the H. Rouse Caffey Rice Research Station near Crowley, LA, to evaluate the influence of a crop oil concentrate (COC), a silicon-based surfactant plus a nitrogen source (SNS), or a high-concentrate COC (HCOC) in overcoming the grass weed control antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na. Quizalofop-p-ethyl was applied at 120 g ai ha−1, bispyribac-Na was applied at 34 g ai ha−1, and all adjuvants were applied at 1% vol/vol. Antagonistic interactions were observed at 14 d after treatment (DAT) when quizalofop-p-ethyl was mixed with bispyribac-Na with no adjuvant for control of barnyardgrass, the non–ACCase-tolerant rice cultivars ‘CL-111’ and ‘CLXL-745’, and red rice. At 14 DAT, antagonism of quizalofop-p-ethyl for control of barnyardgrass was observed when mixed with bispyribac-Na plus COC, SNS, or HCOC, with an observed control of 43%, 63%, and 86%, respectively, compared with an expected control of 95% for quizalofop-p-ethyl alone. However, the antagonism of quizalofop-p-ethyl when mixed with bispyribac-Na plus HCOC for barnyardgrass control at 14 DAT was overcome by 28 DAT, with an observed control of 91%, compared with an expected control of 97%. Synergistic or neutral interactions were observed at 14 and 28 DAT when COC, SNS, or HCOC was added to a mixture of quizalofop-p-ethyl plus bispyribac-Na for CL-111, CLXL-745, and red rice control. According to the results of this study, HCOC is the most effective adjuvant for quizalofop-p-ethyl and bispyribac-Na mixtures for control of weedy rice and barnyardgrass.

Adjuvants for Prohexadione‐Calcium Applied to Alfalfa Interseeded into Corn

Core Ideas Optimal adjuvant selection for ensuring effectiveness of prohexadione‐Ca applied to interseeded alfalfa is unknown. All adjuvants tested provided equivalent effectiveness for prohexadione‐Ca applied to interseeded alfalfa. Supplemental ammonium sulfate did not further enhance the effectiveness of prohexadione‐Ca. Application of the growth retardant prohexadione‐calcium (calcium 3‐oxido‐5‐oxo‐4‐propionylcyclohex‐3‐enecarboxylate; PHD) on interseeded alfalfa (Medicago sativa L.) improves its establishment under silage corn (Zea mays L.). This study evaluated the relative effectiveness of crop oil concentrate (COC), high surfactant oil concentrate (HSOC), methylated seed oil (MSO), and nonionic surfactant (NIS) as adjuvants for commercially formulated PHD (Apogee) when applied with and without supplemental ammonium sulfate (AMS). Acidified solutions of PHD (0.25 kg a.i. ha−1) plus adjuvants were sprayed on 23 to 27 cm tall glyphosate‐resistant alfalfa seedlings that were interseeded immediately after corn planting at two sites in Wisconsin. All PHD–adjuvant–AMS combinations were equally effective, reducing alfalfa height by an average of 16% within 4 wk after treatment and increasing alfalfa stand counts after corn harvest by 30% compared with the non‐PHD treated control. The results suggested a variety of adjuvants may be used when applying PHD to interseeded alfalfa.

Growth Regulation with Lactofen Does Not Affect Seed Yield of Irrigated Soybean

Soybean [Glycine max (L.) Merr.] producers have considered the use of lactofen herbicide (2‐ethoxy‐1‐methyl‐2‐oxoethyl 5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoate) as a growth regulator part of management systems for high‐yielding soybean, believing that lactofen can reduce plant height and lodging or increase node number. Previous research on non‐irrigated soybean was largely unable to show significant benefits for lactofen applied during early vegetative growth (V1–V4) as a growth regulator. However, it is unclear how early‐season lactofen applications affect soybean growth and seed yield in high‐yielding, irrigated soybean management systems common in the midsouthern United States. The purpose of this study was to investigate the effect of early‐season lactofen application on soybean injury, stunting, plant height, node number, intercepted photosynthetically active radiation, lodging, and seed yield at multiple planting dates. Trials were established during the 2013 and 2014 growing season in Stoneville, MS. Soybean was planted at four planting dates: 15 April, 1 May, 15 May, and 1 June. Crop oil concentrate (COC) and lactofen plus COC were applied to soybean at the second trifoliate growth stage (V2). Lactofen plus COC application resulted in early‐season injury and stunting, but did not affect intercepted photosynthetically active radiation, plant height at harvest, lodging, or seed yield while, planting date affected soybean plant height, but did not affect seed yield. The findings of this study suggest that the use of lactofen as a growth regulator for irrigated soybean production in the midsouthern United States is not necessary.Core Ideas Early‐season lactofen application results in temporary injury and stunting in high‐yielding, irrigated soybean in the midsouthern United States. Early‐season lactofen application does not affect soybean seed yield in high‐yield irrigated midsouthern U.S. environments. Soybean planting date failed to affect soybean seed yield in growing seasons with above‐average precipitation.

Evaluation of Saflufenacil in Drill-Seeded Rice (Oryza sativa)

Palmer amaranth is the most common and troublesome broadleaf weed species of rice in Mississippi because of the effects of early-season interference and infestations on rice levees, and herbicides for residual or POST control of Palmer amaranth in rice are limited. Three studies were conducted in 2012 and 2013 to evaluate application rates and timings of saflufenacil in rice and to determine the influence of adjuvants when mixed with saflufenacil applied POST. In a PRE study, no injury occurred after saflufenacil PRE, and no control was observed from carfentrazone. Hemp sesbania and Palmer amaranth control increased with increasing saflufenacil rate when applied PRE. Hemp sesbania control with saflufenacil at any rate PRE was ≤ 25% at 35 d after treatment (DAT). Palmer amaranth and ivyleaf morningglory control with saflufenacil at 75 g ai ha−1PRE was ≥ 94% 35 DAT. In a POST study, rice injury was influenced by application timing and rate of saflufenacil; however, efficacy was not. Rice injury with saflufenacil at 25 g ha−1and carfentrazone early POST (EPOST) and late POST was similar 7 DAT. Saflufenacil at 50 and 75 g ha−1EPOST were the most injurious 7 DAT. Control of hemp sesbania and ivyleaf morningglory was similar for all rates of saflufenacil and carfentrazone; however, Palmer amaranth control with saflufenacil at any rate was greater than that of carfentrazone 14 and 28 DAT. In an adjuvant study, rice injury was influenced by adjuvant and saflufenacil rate. Saflufenacil applied alone or in mixture with crop oil concentrate (COC) was least injurious, and saflufenacil at 50 g ha−1was more injurious than saflufenacil at 25 g ha−1. Saflufenacil applied in combination with any adjuvant provided better control of hemp sesbania and Palmer amaranth than saflufenacil alone. On the basis of this research, saflufenacil should be applied PRE at 50 or 75 g ha−1, depending on weed spectrum, and POST applications should be made at 25 g ha−1in combination with COC after the two-leaf rice growth stage.

Dispersion and evaporation of droplets amended with adjuvants on soybeans

Quantification of the effects of adjuvants on droplet behaviour on plant surfaces is needed to improve pesticide spray application efficiency for soybeans. Dispersion and evaporation of single 300-μm diameter droplets amended with each of four spray adjuvants at five concentrations were investigated for four soybean plant surfaces (abaxial and adaxial leaflet surfaces, petiole, basal stem). The four adjuvants were a crop oil concentrate (COC), a modified seed oil (MSO), a non-ionic surfactant (NIS) and an oil surfactant blend (OSB). A single-droplet generator was used to produce and deposit 300-μm diameter droplets on target surfaces under controlled environmental conditions. Adjuvants significantly increased the dispersion (or wetted area) of droplets on plant surfaces. Droplet-wetted areas increased with increased adjuvant concentrations but not in direct proportion. The average increases of wetted areas across the four soybean plant surfaces were 443, 462, 416, or 343% when the spray mixture was amended with COC, MSO, NIS or OSB at the manufacturer-recommended concentrations, respectively. Among the four surfaces, the largest wetted area was on the abaxial surface, followed by the adaxial surface, the petiole and then the basal stem. Droplet evaporation times were inversely proportional to the wetted areas. The evaporation time of 300-μm diameter droplets ranged from 36 to 142s on the four surfaces when the spray mixture was amended with an adjuvant, whereas the water-only droplets ranged from 161 to 190s. The results demonstrated that use of adjuvants offers great potential to improve the homogeneity of sprayed pesticides, to increase spray coverage and to reduce pesticide application rates on soybean plants. These effects could benefit farmers economically and reduce environmental contamination by pesticides.

Droplet evaporation and spread on waxy and hairy leaves associated with type and concentration of adjuvants

Adjuvants can improve pesticide application efficiency and effectiveness. However, quantifications of the adjuvant-amended pesticide droplet actions on foliage, which could affect application efficiencies, are largely unknown. Droplet evaporation rates and spread on waxy or hairy leaves varied greatly with the adjuvant types tested. On waxy leaves, the wetted areas of droplets containing crop oil concentrate (COC) were significantly smaller than those containing modified seed oil (MSO), non-ionic surfactant (NIS) or oil surfactant blend (OSB), whereas the evaporation rates of COC-amended droplets were significantly higher. On hairy leaves, COC-amended droplets remained on top of the hairs without wetting the epidermis. When the relative concentration was 1.50, the wetted area of droplets with NIS was 9.2 times lower than that with MSO and 6.1 times lower than that with OSB. The wetted area increased as the adjuvant concentration increased. MSO- or OSB-amended droplets spread extensively on the hairy leaf surface until they were completely dried. These results demonstrated that the proper concentration of MSO, NIS or OSB in spray mixtures improved the homogeneity of spray coverage on both waxy and hairy leaf surfaces and could reduce pesticide use. This article is a US Government work and is in the public domain in the USA.

Environmental Effects on Velvetleaf (Abutilon theophrasti) Epicuticular Wax Deposition and Herbicide Absorption

Controlled environment experiments showed that velvetleaf plants grown under drought stress or low temperature (LT) treatments had greater leaf epicuticular wax (ECW) deposition compared to plants grown in soil with moisture at field capacity (FC) or a high temperature (HT) regime. Light intensity did not affect ECW deposition; however, increasing light intensity decreased the leaf ECW ester content and increased the secondary alcohol content. Plants grown at an LT regime or under FC had leaf ECW with fewer hydrocarbons and more esters than those grown at an HT or drought stress regime. Velvetleaf absorption of acifluorfen increased as light intensity decreased for plants grown in adequate soil water content, while the opposite was true for drought-stressed plants. Velvetleaf absorption of acifluorfen was approximately 3 and 10 times greater, respectively, with the addition of 28% urea ammonium nitrate (UAN) in comparison to crop oil concentrate (COC) or no adjuvant, regardless of the environmental treatments. Plants absorbed more acifluorfen when subjected to the LT regime in comparison to the HT regime when UAN was the adjuvant, while the opposite was true when COC was the adjuvant. Velvetleaf absorption of acifluorfen was not affected by drought stress when COC or no adjuvant was used and varied between studies when UAN was used. Velvetleaf absorption of bentazon was greatest for plants grown under HT/FC or high light/FC treatments and least with plants grown under HT/drought stress or low light/drought stress treatments, regardless of the adjuvant. However, bentazon absorption was higher with the addition of an adjuvant and for plants grown at a high light intensity or FC condition compared with medium to low light intensity or drought stress treatments.

Winter Annual Broadleaf Weeds and Winter Wheat Response to Postemergence Application of Two Saflufenacil Formulations

Field experiments in winter wheat were initiated at two locations in the fall of 2006 and 2007 to evaluate winter annual broadleaf weeds and winter wheat response to POST applications of two saflufenacil formulations applied alone and in combination with 2,4-D amine. Emulsifiable concentrate (EC) and water-dispersible granule (WG) formulations of saflufenacil at 13, 25, and 50 g ai ha−1were applied with 1.0% (v/v) crop oil concentrate (COC) and mixed with 2,4-D amine at 533 g ae ha−1without adjuvant. Regardless of rate or formulation, saflufenacil plus COC and saflufenacil plus 2,4-D amine controlled blue mustard ≥ 91% at 17 to 20 d after treatment (DAT) compared with ≤ 50% control with 2,4-D amine alone. At least 25 g ha−1of saflufenacil EC was necessary to control flixweed > 90%. Excluding COC from saflufenacil plus 2,4-D amine reduced flixweed control from the saflufenacil WG formulation more than the EC formulation. Most saflufenacil treatments did not control henbit satisfactorily (≤ 80%). Wheat foliar necrosis increased with increasing saflufenacil rate to as high as 30% at 3 to 6 DAT, but declined to < 15% at 10 to 20 DAT and was not evident at 30 DAT. Saflufenacil rate, formulation, and mixing with 2,4-D amine also influenced wheat stunting, but to a lesser extent than foliar necrosis. Saflufenacil EC consistently caused greater foliar necrosis and stunting on wheat than saflufenacil WG. Leaf necrosis and stunting were reduced by tank-mixing saflufenacil formulations with 2,4-D amine without COC. Grain yields of most saflufenacil treatments were similar to 2,4-D amine under weedy conditions and herbicide treatments had no effect on grain yield in weed-free experiments. Saflufenacil formulations at 25 to 50 g ha−1with 2,4-D amine and saflufenacil WG at 25 to 50 g ha−1with COC can control winter annual broadleaf weeds with minimal injury (< 15%) and no grain yield reductions. The addition of saflufenacil as a POST-applied herbicide would give wheat growers another useful tool to control annual broadleaf weeds, including herbicide-resistant weed species.

Effects of Adjuvants, Halosulfuron, and Grass Herbicides onCucurbitaspp. Injury and Grass Control

Greenhouse experiments were conducted to evaluate pumpkin cultivar injury and control of three grass species from tank-mixtures of halosulfuron with either clethodim or sethoxydim in combination with nonionic surfactant (NIS), crop-oil concentrate (COC), methylated seed oil (MSO), and high-surfactant oil concentrate (HSOC). Pumpkin injury, in the form of chlorosis and visual growth reduction, was 13 to 21% by 7 d after treatment (DAT) for all pumpkin cultivars. The specific adjuvant used with halosulfuron did not influence pumpkin injury or final plant dry weight. Pumpkin growth reduction at 21 DAT from halosulfuron was less than 9% for all pumpkin cultivars with the least growth reduction (5% or less) observed withCucurbita pepo‘Howden’,C. pepo‘Appalachian’, andCucurbita moschata‘Libby's Select’. The efficacy of sethoxydim or clethodim on large crabgrass was antagonized by the addition of halosulfuron with NIS or COC. However, only combinations of sethoxydim and halosulfuron with COC or MSO were antagonistic on smooth crabgrass. Giant foxtail dry weight reduction was decreased 4 to 24% by the addition of halosulfuron to sethoxydim with NIS and clethodim regardless of adjuvant. Although the frequency and magnitude of grass antagonism was variable, the use of clethodim and MSO with halosulfuron most often provided the greatest level of grass control compared with sethoxydim or other adjuvants.

Cyhalofop application timing and adjuvant selection for Echinochloa crus-galli control in rice

Field experiments were conducted in Stuttgart, Arkansas, in 2007 and 2008 to evaluate cyhalofop application timing and adjuvant selection for Echinochloa crus-galli L. Beauv. (barnyardgrass) control in drill-seeded rice. In the application timing experiment, cyhalofop was applied at 1 d prior to flooding (PREFL) and at 7, 14, and 21 d post-flood (POSTFL) as single (314 g a.i./ha) or sequential application (first application at 314 g a.i./ha followed by a second application 14 days later at 213 g a.i./ha). In the adjuvant study, the adjuvants evaluated were non-ionic surfactant (NIS) at 0.25% v/v, crop oil concentrate (COC) at 1% v/v, methylated seed oil (MSO) at 1% v/v, 28% urea ammonium nitrate (UAN) at 2.5% v/v, combination of NIS or COC or MSO with UAN, a proprietary blend of MSO/organosilicone (OSL)/UAN at 2.5% v/v, and MSO/OSL/UAN applied with NIS or COC. All adjuvants applied with cyhalofop (314 g a.i./ha at 14 d after flood establishment) resulted in E. crus-galli control and rice yields comparable to cyhalofop alone. In 2007, a single application of cyhalofop controlled E. crus-galli 98–100% by the end of the season, except in the 14-d POSTFL timing (90%). In 2008, E. crus-galli plants were more robust, and control was inconsistent and less than in 2007 (10–91%). At the PREFL timing, sequential applications were needed to improve end-of-season E. crus-galli control. The 7-d POSTFL timing was one of the best single application timings for increased E. crus-galli control and rice yield. Delaying the cyhalofop application to 21-d POSTFL resulted in unacceptable E. crus-galli control of 10 and 46% with single and sequential programs, respectively. Average rice yield was reduced almost three-fold when the first cyhalofop application was at 21-d POSTFL compared with 7-d POSTFL.

Tolerance of winter wheat ( Triticum aestivum L.) to pre-emergence and post-emergence application of saflufenacil

Saflufenacil is a new herbicide being developed for pre-plant burndown for non-selective removal of broadleaf weeds and pre-emergence (PRE) broadleaf weed control in field crops, including maize, soybean, sorghum and wheat. As part of studying the potential use pattern of this herbicide, four field studies were conducted in 2006 and 2007 at Concord, northeast Nebraska, to determine winter wheat tolerance to PRE and post-emergence (POST) applications of saflufenacil. The fall POST applications were conducted at the 2–3 leaf stage (5 cm height) whereas the spring POST and tank-mixes studies were sprayed at the 4th node stage (40 cm height) of crop. Dose-response curves based on log-logistic model were used to determine the ED (effective dose) values of saflufenacil for visual ratings of crop injury and relative yield. There was no crop injury or yield reduction with PRE applied saflufenacil dose of up to 400 g a.i. ha −1. However, there was significant crop injury in the POST applications in the fall (up to 95%) and in the spring (up to 67%). There was also yield reduction of as much as 66% in the fall and 58% in the spring POST applications. Addition of adjuvants also increased crop injury levels. For example, at 14 days after treatment in the fall applications, about 5% visual crop injury (ED 5) was evident with 82, 67 and 10 g a.i. ha −1 of saflufenacil compared with 51, 30 and 11 g a.i. ha −1 in the spring, with no adjuvant, or non-ionic surfactant (NIS), or crop oil concentrate (COC), respectively. Saflufenacil at half the proposed used dose of 25 g a.i. ha −1 was safe to mix with the currently used POST herbicides of wheat with no visible crop injury and yield reduction. PRE applications of saflufenacil would be safe for use in winter wheat; however, the POST application of saflufenacil alone or with the adjuvant NIS or COC produces unacceptable injury and yield loss. These results are similar to the proposed PRE use pattern of saflufenacil. In addition, the proposed label does not suggest the POST use of saflufenacil in winter wheat, or any other cereal crops, which is similar to what we have concluded from this study.

Application timing and adjuvant type affected saflufenacil efficacy on selected broadleaf weeds

Saflufenacil is a new herbicide being developed for pre-plant burndown and pre-emergence broadleaf weed control in field crops, including maize, soybean, sorghum and wheat. Field experiments were conducted in 2007 and 2008 in northeast Nebraska, USA to describe dose-response curves of saflufenacil applied in mid (early post-emergence, EPOST) and late May (late post-emergence, LPOST) with several adjuvants for spring emerging broadleaf weed control. Dose-response curves based on log-logistic model were utilized to determine the ED 90 values (effective dose that provides 90% weed control efficacy) for Convolvulus arvensis, Lactuca serriola, Lamium amplexicaule, Capsella bursa-pastoris, Taraxacum officinale, Thlaspi arvense and Conyza canadensis. In general, weed control efficacy was influenced by application timing and type of adjuvant. EPOST application of saflufenacil resulted better efficacy of saflufenacil compared to LPOST. Addition of spray adjuvants improved efficacy of saflufenacil. For example, 90% control of T. arvense was obtained at EPOST application with 251, 161, 96 and 59 g a.i. ha −1 for saflufenacil applied alone, or tank-mixed with NIS (nonionic surfactant), COC (crop oil concentrate), or MSO (methylated seed oil), respectively. In contrast, the ED 90 values with LPOST application were 333, 201, 127 and 79 g a.i. ha −1 for saflufenacil applied alone, or with NIS, COC and MSO, respectively. MSO was the best adjuvant, which provided the most enhancement of saflufenacil. COC was the second best, or similar to MSO, on many weed species. NIS provided the least enhancement of saflufenacil. The ED 90 values determined for different broadleaf weed species are within the proposed label dose of saflufenacil.

Adjuvants Influenced Saflufenacil Efficacy on Fall-Emerging Weeds

Saflufenacil is a new herbicide being developed for preplant burndown and PRE broadleaf weed control in field crops, including corn, soybean, sorghum, and wheat. Field experiments were conducted in 2006 and 2007 at Concord, in northeast Nebraska, with the objective to describe dose–response curves of saflufenacil applied with several adjuvants for broadleaf weed control. Dose–response curves based on log-logistic model were used to determine the effective dose that provides 90% weed control (ED90) values for six broadleaf weeds (field bindweed, prickly lettuce, henbit, shepherd's-purse, dandelion, and field pennycress). Addition of adjuvants greatly improved efficacy of saflufenacil. For example, the ED90values for field bindweed control at 28 d after treatment were 71, 20, 11, and 7 g/ha for saflufenacil applied alone, or with nonionic surfactant (NIS), crop oil concentrate (COC), or methylated seed oil (MSO), respectively. MSO was the adjuvant that provided the greatest enhancement of saflufenacil across all species tested. COC was the second-best adjuvant and provided control similar to MSO on many weed species. NIS provided the least enhancement of saflufenacil. These results are very similar to the proposed label dose of saflufenacil for burndown weed control, which will range from 25 to 100 g/ha with MSO or COC. We believe that such a dose would provide excellent burndown control of most broadleaf weed species that emerge in the fall in Nebraska.

Proper adjuvant selection to enhance the activity of triclopyr combined with metsulfuron on the control of Hedyotis verticillata

A study was conducted to evaluate the combined activity of a tank mixture of triclopyr plus metsulfuron with non‐ionic surfactant (NIS), crop oil concentrate (COC), and organosilicon (OS) adjuvants on the control of Hedyotis verticillata under glasshouse and field conditions. The results of both the glasshouse and field experiments showed that 160 g ai ha−1 triclopyr plus 0.2 g ai ha−1 metsulfuron and 320 g ai ha−1 triclopyr plus 0.4 g ai ha−1 metsulfuron, with the addition of 0.25% NIS, 0.05% COC, or 0.05% OS, were effective in controlling H. verticillata. A comparison of the cost revealed that the most cost‐effective combination for controlling H. verticillata is 160 g ai ha−1 triclopyr plus 0.2 g ai ha−1 metsulfuron combined with 0.25% NIS.

The Influence of Tank Mix Additives While Making Low Volume Aerial Fungicide Applications

Abstract Multiple experiments using low volume aerial applications with nine different adjuvants in combination with fungicide were conducted to compare coverage, droplet spectra, yield, and disease control. Four locations were scattered over three states: Arkansas, Kansas, and Illinois. Four aircraft with different nozzle and boom setups were used to complete the studies. Volume median size (DV0.5) ranged from 232 μm to 364 μm. Kromekote® papers used as collectors were placed in the center 9 m of each aerial swath/treatment (20 m) at three different plant heights: top corn leaf, ear leaf, and the leaf three collars below ear leaf. In each treatment, sampling consisted of 30 papers; 10 corn plants at the three heights, with all papers at 30 cm from the main stalk. DropletScan™, utilizing a high resolution color scanner to digitize the images on the Kromekote® papers, was used to analyze each paper. Means for percent area coverage and DV0.5 were used to separate differences in treatments. Relative span was calculated as an indicator of the range in the droplet spectrum. Yields were taken from the center of each treatment. Three to five replications per treatment were completed and a SAS GLIMMIX analysis was performed. Significant differences were measured among adjuvant treatments for both droplet spectra and deposition/coverage. Mixed results are reported across all treatments and locations. A mixture of water, Headline, and Crop Oil Concentrate (Treatment 2) was consistently measured with the lowest amount of coverage, and in two of four locations had the largest DV0.5. Overall, droplet spectra were impacted by the addition of adjuvants to the tank mix. The largest droplets were not associated with the best coverage, and the trend was for the lowest coverage to be associated with the smallest droplets. Treatment 5 (NIS+Interlock) had the smallest DV0.5 in three of the test locations. A limited number of significant yield differences were found. This effect could be due to low disease pressure.

Urea Ammonium Nitrate Effects on Bispyribac and Penoxsulam Efficacy

Experiments were conducted at the Lonoke Extension and Applied Research Center greenhouse at Lonoke, AR, to evaluate the effects of urea ammonium nitrate (UAN) on bispyribac and penoxsulam efficacy on barnyardgrass, hemp sesbania, and broadleaf signalgrass. Herbicide treatments included bispyribac at 17.9 or 35.8 g ai/ha or penoxsulam at 24.4 or 48.9 g ai/ha tank mixed with (1) no adjuvant, (2) a nonionic organosilicone (OSL) adjuvant at 0.125% v/v, (3) a methylated seed oil/organosilicone (MSO/OSL) adjuvant at 0.37 L/ha, (4) a proprietary blend of MSO/OSL/UAN at 2% v/v, (5) UAN at 2% v/v, (6) OSL at 0.125% plus UAN at 2% v/v, or (7) MSO/OSL at 0.37 L/ha plus UAN at 2% v/v. In addition to these adjuvants, penoxsulam was also applied with crop oil concentrate (COC) at 2.34 L/ha and with COC at 2.34 L/ha plus UAN at 2% v/v. The addition of UAN to either herbicide plus an adjuvant increased herbicide efficacy on barnyardgrass in the greenhouse, with 95 to 99% biomass reduction of three- to four-leaf barnyardgrass and 88 to 92% biomass reduction of one- to three-tiller barnyardgrass. UAN did not generally increase efficacy on hemp sesbania, as control was 90% or higher with treatments containing either herbicide and a recommended adjuvant. Adding UAN did not increase efficacy on broadleaf signalgrass. Broadleaf signalgrass control was highly variable and no treatment provided more than 65% biomass reduction.

Halosulfuron Tank Mixtures and Adjuvants for Weed Control in Pumpkin Production

Field studies were conducted to evaluate postemergence combinations of halosulfuron plus sethoxydim or clethodim with various adjuvants for effects on jack-o-lantern pumpkin (Cucurbita pepo L.) injury and yields and control of large [Digitaria sanguinalis (L.) Scop.] and smooth crabgrass [D. ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl.]. Halosulfuron caused 27% and 14% pumpkin injury at 28 d after postemergence treatment (DAPT) in 2004 and 2005, respectively. Tank-mixing sethoxydim or clethodim with halosulfuron did not increase pumpkin injury compared with halosulfuron alone. Pumpkin injury from sethoxydim and clethodim alone at 28 DAPT ranged from 19% to 23% in 2004, but was only 7% to 8% in 2005. The addition of oil-based adjuvants to halosulfuron did not affect pumpkin injury compared with using a nonionic surfactant (NIS). The tank mixture of halosulfuron and sethoxydim did not affect crabgrass control regardless of adjuvant. However, the addition of halosulfuron to clethodim plus NIS reduced control of crabgrass from 89% to 77% at 28 DAPT. Crabgrass control was unaffected by the addition of halosulfuron to clethodim with crop oil concentrate (COC) or a NIS/COC blend. None of the herbicide treatments provided pumpkin yield (fruit no./ha) similar to the weed-free control. The pumpkin yield of treatments using postemergence herbicides was at least 50% less than the weed-free treatment. These low pumpkin yields were most likely the result of the combination of pumpkin injury from the herbicide applications and insufficient weed control.