Woody plant herbicide screening techniques were evaluated to expedite the screening process and decrease amounts of herbicide active ingredient required. Rapid greenhouse screening of woody plant seedlings was performed in less than 6 months, and rapid seed screening was performed in less than 20 days. A traditional field screen, requiring 10 months from application to final evaluation, was performed for comparison and regression modeling purposes. Imazapyr and triclopyr were used as test chemicals and linear regressions were generated to predict traditional field screen results from rapid screens. Significant regressions were produced that predicted field responses of loblolly pine, sweetgum, and yellow-poplar with the use of both herbicides and either rapid screening technique. This indicated that rapid screening techniques could determine herbicide efficacy and/or species spectrum in much less time with significantly less herbicide. Rapid greenhouse screens of triclopyr produced more statistically significant regressions than those using imazapyr. Rapid seed screens could estimate species spectrum within 5 days after treatment. These results indicate that rapid greenhouse screen and rapid seed screen techniques can provide woody plant herbicide developers initial efficacy and spectrum of control data in a cost- and-time effective manner.

In an effort to find safe natural products to function in traditional agricultural chemical roles, short-chain fatty acids were evaluated as desiccants for dry beans. Desiccation was evaluated in greenhouse studies on three dry bean cultivars: ‘Montcalm’ kidney, ‘Midnight’ black turtle, and ‘Vista’ navy bean. Caprylic (C8) and pelargonic acid (C9) were the most effective in the C2 through C10 range. Effective emulsifiers with C8 were Henkel Emsorb 6900 and Henkel Emsorb 6915. Organosilicone, saponified, methylated, and ethylated seed oil activator adjuvants enhanced the efficacy of the caprylic acid. C8 was also phytotoxic to velvetleaf, giant foxtail, and common lambsquarters; esters of C6, C8, and C10 fatty acids were comparatively less effective than C8.

Studies were conducted in 1999, 2000, and 2001 to evaluate broadleaf weed control in cotton from POST applications of trifloxysulfuron plus pyrithiobac. Trifloxysulfuron was applied at 2.5, 5, and 7.5 g ai/ha, and pyrithiobac was applied at 0, 17, and 35 g ai/ha in a factorial treatment arrangement. Cotton injury was affected by rates of both herbicides at 7 and 14 d after treatment (DAT) with injury ranging from 19 to 26%. Broadleaf weed control at 28 DAT from mixtures of the herbicides was generally commercially acceptable. Combinations of 17 or 35 g/ha pyrithiobac plus trifloxysulfuron controlled common ragweed, velvetleaf, common lambsquarters, annual morningglory species (ivyleaf morningglory, pitted morningglory, and tall morningglory), common cocklebur, spurred anoda, and jimsonweed at least 73% at 28 DAT. Trifloxysulfuron applied alone failed to control velvetleaf, spurred anoda, and jimsonweed. Cotton yield reflected weed control and yields increased with pyrithiobac rates. It is concluded that the spectra of the weeds controlled by trifloxysulfuron and pyrithiobac were highly complementary in these studies.

Weed interference experiments have not been extensively conducted in Oklahoma peanut. Research was conducted in three environments to evaluate usefulness of single-weed density experiments with the use of several weeds to measure their relative competitive abilities with a crop. These data can be used to validate current competitive indices (CIs) used by a model to predict peanut yield loss due to weeds. This model is used by the Herbicide Application Decision Support System (HADSS) and Pesticide Economic and Environmental Tradeoffs (PEET), two decision-support systems (DSSs) available for Oklahoma peanut. Six weeds common in Oklahoma peanut were used: crownbeard, eclipta, ivyleaf morningglory, johnsongrass, Palmer amaranth, and prickly sida plus two others, barnyardgrass and common cocklebur, as benchmark species. Each weed was planted into peanut uniformly at eight weeds/10 m of row. Dry weed biomass accounted for 77 to 90% of variation in in-shell peanut yield loss; however, model parameters only allow for weed number. Yield losses from these experiments were compared to those predicted by the model to test original CI accuracy. Treatment means were compared to the prediction model with the use of protected LSD. Several significant differences were noted, and the CIs for those weed species were adjusted accordingly. Adjusting CIs improved actual yield data goodness of fit to model predictions specific to environment in question, but not necessarily in different environments. The CI changed at Ft. Cobb were eclipta from 1.8 to 4.5 and ivyleaf morningglory from 3.4 to 5.0. CI adjustments at Perkins were common cocklebur from 10.0 to 5.8 and johnsongrass from 3.0 to 4.6. Collecting data for several weed species at uniform density in a crop provides a more time-efficient method for obtaining accurate relative weed interference data; this method is useful in validating or establishing CI lists in areas and/or crops with limited data.

Growers from three counties in Virginia have recently experienced difficulty controlling shattercane in corn with acetolactate synthase (ALS)–inhibiting herbicides. Seed was collected from these locations and from a susceptible biotype and tested for resistance to imazethapyr, imazapyr, and nicosulfuron in greenhouse trials. Seedlings from these locations were also treated with glufosinate and glyphosate. Greenhouse experiments indicated that one of the four shattercane biotypes was resistant to ALS-inhibiting herbicides. Effective control of the resistant biotype was possible with glufosinate or glyphosate. Field experiments were conducted in 2003 and 2004 to determine the most effective herbicide program utilizing herbicide-tolerant/-resistant corn hybrids for the control of shattercane. Early postemergence (EP) and late postemergence (LP) applications of imazethapyr plus imazapyr or EP nicosulfuron did not control shattercane, and yield from the imidazolinone-tolerant (IT) hybrid was equivalent between these treatments and was equivalent to yield from the weedy control (WC). At 23 wk after planting (WAP), EP applications of glyphosate controlled shattercane 71 and 75% compared to only 21 and 66% with EP applications of glufosinate in 2003 and 2004, respectively. In both years, LP applications of glufosinate or glyphosate controlled shattercane better than did EP applications of glufosinate or glyphosate. Treatment timing with respect to corn yield within either the glufosinate-resistant (LL) or glyphosate-resistant (RR) corn hybrid was critical. EP treatments of glufosinate or glyphosate resulted in yields that were equivalent to yield from the weed-free control (WFC) of each hybrid. LP treatments of glufosinate or glyphosate, however, resulted in yields that were equivalent to only 90 and 91% of yield from the WFC of each hybrid, respectively.

Greenhouse and laboratory experiments were conducted to investigate the response of common lambsquarters to POST applications of halosulfuron–methyl plus 2,4-D admixtures and to investigate the effects of 2,4-D on the absorption, translocation, and metabolism of halosulfuron. In the greenhouse, halosulfuron at 0, 4.5, 9, 18, and 36 g ai/ha was applied alone and mixed with 2,4-D at 0, 17, 35, and 70 g ai/ha POST to 7.5- to 9-cm seedlings, and plant fresh weights were determined 4 wk after treatment (WAT). Halosulfuron alone did not control this weed, while fresh weights of common lambsquarters treated with 2,4-D declined hyperbolically as rates increased. A synergistic response for mixtures of these herbicides occurred, as observed fresh weights for all combinations were less than expected based on independent action and the calibrated marginal responses. In the laboratory, 7.5- to 9-cm seedlings were treated POST with commercially formulated halosulfuron at 9 and 18 g/ha and 2,4-D at 0, 70, and 140 g/ha, respectively, followed by foliar-applied 14C-halosulfuron. Absorption of 14C-halosulfuron increased with time, and absorption and translocation were not influenced by the addition of 2,4-D. Results from these studies inferred that halosulfuron and 2,4-D were generally synergistic on common lambsquarters and that mechanisms other than absorption, translocation, and metabolism may explain this response.

Johnsongrass control in fallowed sugarcane fields was evaluated with glyphosate and the graminicides quizalofop, fluazifop, and clethodim applied in soybean compared with nonsoybean tillage and glyphosate programs. Glyphosate was applied to glyphosate-resistant soybean as a single early postemergence (EPOST) treatment around 30 d after planting (DAP) at rates of 840, 1,120, or 2,240 g ai/ha; as sequential treatments EPOST and late postemergence (LPOST) around 60 DAP at 560 followed by (fb) 560 or 1,120 fb 1,120 g/ha; or as a single LPOST treatment at 2,240 g/ha. Quizalofop at 77 g ai/ha, fluazifop at 420 g ai/ha, and clethodim at 280 g ai/ha were also evaluated as single EPOST treatments. In 1996 johnsongrass control 7 d after EPOST treatment (DAT) was at least 90% for glyphosate treatments but control was 73 to 77% for the graminicides. In 1997 johnsongrass control 7 DAT was at least 82% for all herbicide treatments. Excellent johnsongrass control approximately 50 DAT was achieved both years with all the glyphosate and graminicide treatments. In the nonsoybean fallow weed control programs where plots were tilled twice or three times fb one or two glyphosate applications, complete control of johnsongrass was obtained both years. In 1996 when glyphosate was applied EPOST or EPOST fb LPOST, soybean yields were equivalent and averaged 3.3 times that of the single LPOST glyphosate application. Soybean yields where the graminicides were used and where glyphosate was applied as a single LPOST treatment were no greater than the nontreated control. Economic analysis on the basis of soybean yield data and variable costs of herbicides, seed, field application, seedbed preparation, tillage, labor, fuel, repairs, and custom harvest expense in 1996 showed a positive net return only for glyphosate applied EPOST at 840 g/ha ($99.82/ha) or 1,120 g/ha ($46.94/ha) and for glyphosate applied at 560 g/ha EPOST fb LPOST ($10.41/ha). Although showing a negative net return, glyphosate applied EPOST at 2,240 g/ha ($−8.32/ha) or EPOST fb LPOST at 1,120 g/ha ($−50.97/ha), the loss was less than that for nonsoybean fallow tillage and glyphosate programs ($−155.70/ha and $−157.78/ha). In 1997, when soybean was not harvested because of environmental conditions, variable costs exceeded those of the nonsoybean programs, indicating that planting soybean strictly as a cover crop would not be economically advantageous. Sugarcane growth and yield the year following the fallow programs was not negatively affected by production of soybean regardless of herbicide program.

The response of the sugarcane cultivars HoCP 91-555, HoCP 85-845, and LCP 85-384 to flumioxazin during the first (plant cane) and second (first ratoon) production years was evaluated within two identical experiments, the first starting in 2000 and the second in 2001. In the plant-cane crop, flumioxazin application timings were PRE immediately following planting, fall postemergence (FPOST) 6 wk after planting, early spring postemergence (ESPOST), postemergence-directed spray (PDS) following layby cultivation, and sequential applications of FPOST followed by ESPOST. During the first-ratoon crop, flumioxazin was applied ESPOST, late-spring (LSPOST), PDS following layby cultivation, and sequentially LSPOST followed by PDS. Flumioxazin injury to sugarcane consisted mainly of stunted growth and reddening and necrosis of treated leaves. In plant cane, injury was 28% 2 wk after treatment (WAT) when applied ESPOST in one experiment but less than 10% in the other, and was no more than 13% in either experiment at 6 WAT. In the first-ratoon crop, injury was around 15% when applied ESPOST in the first experiment, but no injury was observed 6 WAT. However, in the first ratoon, injury to all cultivars was 25 to 30% when following a LSPOST application. When applied as a PDS, injury was no more than 15% 4 WAT in either plant-cane or first-ratoon sugarcane. Stalk height was reduced 15 cm compared to the nontreated control when flumioxazin was applied as a sequential application (FPOST followed by ESPOST) in plant cane and by 23 cm (LSPOST followed by PDS) in first-ratoon sugarcane. In plant cane ESPOST applications of flumioxazin reduced sugar yield (9 to 28%) within all three cultivars used in this study in both experiments with only one exception. Sequential (FPOST followed by ESPOST) applications reduced sugar yield within all cultivars (6 to 37%). PDS applications at layby reduced yields (7 to 12%) in the first experiment, but not in the second experiment. In the first-ratoon crop, LSPOST applications of flumioxazin reduced sugar yield (7 to 11%), sequential flumioxazin applications (LSPOST followed by PDS) reduced sugar yields (8 to 19%), and PDS applications at layby did not reduce yield. It appears that there is little if any difference in tolerance to flumioxazin for the cultivars used in this experiment. To avoid risk of yield loss, flumioxazin should not be applied as an over-top POST treatment to weeds in actively growing sugarcane, and care should be taken to minimize spray contact with sugarcane leaves when applying flumioxazin as a PDS at layby.

Herbicide evaluation trials are typically conducted with the objective of rating herbicide efficacy and assessing crop yield loss. There is little if any attempt to quantify the economic risk associated with each treatment. The objective of this research was to use second-degree stochastic dominance to evaluate the economic stability of corn and soybean weed management systems between two contrasting environments. Weed management systems were evaluated in small-plot replicated trials over a 3-yr time period at two locations in southern Minnesota. One location (Waseca) had a slightly cooler and wetter environment than the second location (Lamberton). The Waseca location also had higher weed density and greater weed species diversity. Adjusted returns from weed management were calculated for each system by measuring economic returns, as determined by deducting weed management costs from the product of crop price and grain yield. Stochastic dominance is a technique that considers the entire distribution of net returns from weed management and compares these cumulative distributions as a basis for analyzing risk. Climate, soils, and weed diversity dictated differences in risk efficiency and effectiveness of the various weed management systems evaluated between the Waseca and Lamberton sites. Stochastic dominance testing is a useful tool for understanding long-term risk across environments. Results can be used to develop effective long-term weed management systems that minimize risk while maximizing profit potential.

Research was conducted to determine the minimum number of between-row mowings necessary to control annual weeds, chiefly giant foxtail and common waterhemp, without corn yield loss. Over 2 yr in Missouri, the between-row mowing systems that were evaluated consisted of a 38-cm band of PRE atrazine plus metolachlor at 2.2 plus 2.2 kg ai/ha applied over corn grown in 76-cm rows shortly after planting followed by one, two, or three between-row mowings close to the soil surface. Based on rated total weed control, between-row total weed cover, and corn yield, the weed-free check was statistically indistinguishable from a treatment in which banded PRE herbicide was followed by only one between-row mowing, late, when weeds were relatively large. When mowed once at 52 to 64 days after planting (DAP), giant foxtail and common waterhemp were greater than 85 cm tall. The yield was not increased by mowing earlier or more than once.

A replacement series study was conducted to describe the aggressivity between cucumber, smooth pigweed, and livid amaranth. Cucumber was three times more competitive than smooth pigweed or livid amaranth, under the conditions of this study. However, there was equal competition and no antagonism between smooth pigweed and livid amaranth. Where cucumbers were planted in mixture with either of the two weeds, the relative yield total values were approximately 10 to 20% higher than the monocultures. Cucumber was a superior competitor when grown in mixture with smooth pigweed or livid amaranth, and the following aggressivity hierarchy exists: cucumber > livid amaranth = smooth pigweed. Results from the additive field study indicated that amaranth dry weights were significantly affected by smooth pigweed and livid amaranth density. Dry weight of amaranth was decreased by 48% at Gainesville and 25% at Live Oak, at 18 plants/m2. Despite differences between the Gainesville and Live Oak results, the dry weight data were similar for both smooth pigweed and livid amaranth at each location.

Studies were conducted for 12 wk from June 16 to September 8, 2003 and July 10 to October 4, 2004 with the objective of evaluating growth regulation, lateral regrowth, and injury of Tifway bermudagrass [Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy Tifway] in response to two GA-inhibiting plant growth regulators, trinexapac-ethyl and flurprimidol. Trinexapac-ethyl was applied alone at 0, 0.052, and 0.104 kg ai/ha and flurprimidol alone at 0, 0.14, and 0.28 kg ai/ ha, plus all combinations. Applications were made every 3 wk for the duration of the study. Tifway bermudagrass clipping yield was reduced 33% and 54% by trinexapac-ethyl at 0.104 kg/ha at 4 and 8 wk after initial treatment (WAIT), respectively. Flurprimidol at 0.28 kg/ha reduced clipping yield 49% 8 WAIT. Lateral regrowth was reduced 20% 2 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 26% 2 WAIT by flurprimidol at 0.28 kg/ha. Lateral regrowth was reduced 13% 4 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 15% 4 WAIT by flurprimidol at 0.28 kg/ha. Overall, acceptable injury (<30%) was observed with a trinexapac-ethyl and flurprimidol tank mixture; however, this evaluation did not indicate an advantage in growth regulation when using a tank mixture of these products, compared to using them alone.

The “micro-rate” application, a POST combination of desmedipham plus phenmedipham at 0.045 + 0.045 kg ai/ha (desphen) or desmedipham plus phenmedipham plus ethofumesate (1:1: 1 ratio) (desphenetho) at 0.09 kg ai/ha plus triflusulfuron at 0.004 kg ai/ha plus clopyralid at 0.026 kg ae/ha plus 1.5% methylated seed oil received registration in 1998 and 2000 in North Dakota and Michigan, respectively. Herbicide rates are reduced by 80%, compared to standard-split applications, and growers typically apply the micro-rate three to five times to very small weeds that are 1 cm or less in height. In standard-split applications, growers make two sequential applications, the first when weeds are 1.5 cm tall and the sequential application usually 10 to 14 d later. Research was conducted in small plots and large grower plots in 2001 and 2002 to determine the effect of PRE herbicides on weed control and sugarbeet injury from micro-rates compared to standard-split POST herbicide applications. Sugarbeet populations were reduced in the cycloate treatment compared to all other PRE and the no-PRE treatment in 2001 and in the S-metolachlor compared to the ethofumesate treatment in 2002. Sugarbeet injury was 6% or less from POST-only treatments in 2001. Control of common lambsquarters and Amaranthus spp. by desphen and desphenetho treatments was similar. Sugarbeet injury in 2002 was 29 to 43% from POST-only treatments. The standard-split of desphenetho was more injurious than the standard-split of desphen. Common lambsquarters control was greater in both the standard-split and micro-rate of desphenetho compared to the standard-split of desphen in 2002. However, sugarbeet populations and recoverable white sucrose per hectare did not differ among POST herbicide treatments in either year. No herbicide program provided 100% control of all weeds in both years. In the seven large production fields, PRE herbicide treatments did not reduce sugarbeet populations or recoverable sucrose per hectare compared to the no-PRE control. Weed control from four POST micro-rate applications only was similar to weed control in instances in which PRE herbicides were applied prior to the POST micro-rate applications.

The potential for future commercialization of glyphosate-resistant wheat necessitates evaluation of agronomic merits of this technology. Experiments were established to evaluate glyphosate-resistant wheat and weed responses to glyphosate rate, application timing, and tank mixtures. Glyphosate at 1,680 g/ha did not injure wheat. Wheat response to glyphosate applied to one- to three- or three- to five-leaf wheat was not different from that of untreated wheat. Wheat was injured more from glyphosate plus thifensulfuron or glyphosate plus dicamba than from individual herbicides at one of six locations, but grain yield was not affected by glyphosate tank mixtures. Glyphosate application timing did not affect control of wild oat or common lambsquarters 56 d after treatment. Glyphosate when applied to one- to three-leaf wheat provided better control of wild buckwheat than later glyphosate application, whereas glyphosate applied to three- to five-leaf wheat provided the best control of green and yellow foxtail, redroot pigweed, and Canada thistle. Weed control with glyphosate tended to be better than with conventional herbicides, and wheat treated with glyphosate produced approximately 10% more grain than wheat treated with conventional herbicide tank mixes.

Persian darnel control options are limited and unmanaged populations can cause substantial crop yield loss. Integrating crop diversification and higher crop seeding rates into a cropping system might improve Persian darnel management. Field experiments were conducted to determine the effect of different crops and increased crop seeding rates on Persian darnel fecundity. Persian darnel produced up to 2,800 seeds per plant and 53,000 seeds/m2 when grown without competition. Increasing crop density reduced Persian darnel tillers per plant, seed weight, and fecundity. Increasing crop density reduced Persian darnel fecundity 0.4 to 0.2% per spring wheat plant, 0.6 to 0.1% per canola plant, and 16 to 8% per sunflower plant. Persian darnel fecundity was impacted the greatest by reduced weed seedling establishment, which was caused by crop competition and seeding sunflower late in the spring preceded by a nonselective herbicide application. Results indicated delaying the seeding of spring crops or including a late-seeded warm season crop, like sunflower or safflower, in the cropping system is an effective weed management tool for reducing Persian darnel fecundity.

Experiments were conducted to study the effect of application rate, growth stage, and tank-mixing azimsulfuron or bentazon on the activity of cyhalofop, clefoxydim, and penoxsulam against two morphologically distinct Echinochloa species from rice fields in Greece. Mixtures of penoxsulam with MCPA were also evaluated. Cyhalofop (300 to 600 g ai/ha) applied at the three- to four-leaf growth stage provided 62 to 85% control of early watergrass but 41 to 83% control of late watergrass averaged over mixture treatments. Control ranged from 37 to 80% for early watergrass and from 35 to 78% for late watergrass when cyhalofop was applied at the five- to six-leaf growth stage averaged over mixture treatments. Mixtures of cyhalofop with azimsulfuron or bentazon reduced efficacy on both species irrespective of growth stage or cyhalofop application rate compared with cyhalofop alone. Clefoxydim (100 to 250 g ai/ha) applied alone at the three- to four-leaf growth stage provided 98 to 100% control of early watergrass and 91 to 100% control of late watergrass; when clefoxydim was applied alone at the five- to six-leaf growth stage the control obtained was 91 to 100% for early watergrass and 79 to 100% for late watergrass. Mixtures of clefoxydim with azimsulfuron or bentazon reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Penoxsulam (20 to 40 g ai/ha) applied alone provided 94 to 100% control of both species at both growth stages. Mixtures of MCPA with penoxsulam reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Mixtures of penoxsulam with azimsulfuron or bentazon reduced efficacy only on late watergrass at the late growth stage.

Experiments were conducted to investigate the effects of depth and duration of burial on seasonal germination, primary and secondary dormancy, viability, and seedling emergence of ivyleaf speedwell (Veronica hederifolia L.) seeds. The seeds were buried at 0, 5, 10, or 20 cm and retrieved from the field at monthly intervals. The exhumed seeds were germinated at 5 C. In the second experiment, seeds were stored in the laboratory after harvest and tested for germination at monthly intervals. In each experiment, nongerminated seeds were treated with triphenyltetrazolium chloride at monthly intervals to test their viability. The effects of stratification and burial depth on seedling emergence were observed for 1 yr. The seeds exhumed from the soil were dormant at the beginning of the experiment and exhibited dormancy/nondormancy/conditional dormancy cycling throughout the experiment. Depth of burial and time affected seed germination. Seeds retrieved from the soil surface germinated well initially, but germination decreased as depth of burial increased. In the dry storage experiment, seeds had a high level of primary dormancy, and viability decreased over time. Seedling emergence decreased when depth of burial increased. Seedlings emerged nonuniformly throughout the year and demonstrated typical winter annual characteristics.

During routine use of fluazifop-P-butyl for grass control, county extension agents in Georgia observed control of bristly starbur in grower fields. Experiments to characterize the activity of fluazifop-P-butyl on bristly starbur were conducted under greenhouse conditions in Gainesville, FL, during 2001 and 2002. Fluazifop-P-butyl activity was characterized as a function of herbicide rate and time after application. Commercially available fluazifop-P-butyl was compared to technical fluazifop-P-butyl as a function of herbicide rate and bristly starbur height. Finally, injury to bristly starbur was evaluated when clethodim, diclofop, fluazifop-P-butyl, haloxyfop, quizalofop-p, and sethoxydim were applied at two growth stages. Fluazifop-P-butyl caused >90% injury to bristly starbur with all other post graminicides displaying <8% injury. Nonlinear regression revealed a sigmoidal response of bristly starbur injury to fluazifop-P-butyl. Estimates for 50 and 90% bristly starbur injury (I50 and I90) were 0.07 and 0.14 kg ai/ha, respectively. There was no difference in activity of technical and commercial fluazifop-P-butyl formulations. There was a differential response of bristly starbur to fluazifop-P-butyl over time as a function of plant height at the time of treatment. However, 14 days after treatment (DAT) all treatments displayed >89% injury. Bristly starbur response to fluazifop-P-butyl was similar to injury associated with contact-type herbicides.

The objectives of this research were to evaluate herbicide safeners and water repellents for their efficacy in reducing injury caused by isoxaflutole to corn at four application timings (PRE, spike, two-leaf, and four-leaf), and to evaluate the retention of the combinations of isoxaflutole, herbicide safeners, and water-repellent adjuvants. The safeners R-29148 and furilazole decreased injury from isoxaflutole when applied PRE. Corn injury increased from POST applications at the two-leaf and four-leaf stage of isoxaflutole mixed with safeners compared with isoxaflutole alone. The safeners may have acted as adjuvants to increase isoxaflutole absorption. The water-repellent adjuvants did not reduce injury when applied POST with isoxaflutole. However, the combination of safener plus the water repellent DC 1-6184 reduced corn injury from POST applications of isoxaflutole. The water repellent DC 1-6184 reduced spray retention of spray solutions containing isoxaflutole or isoxaflutole plus safener.

Trials were conducted under weed-free conditions in 2001, 2002, and 2003 on a loamy sand soil in Georgia to investigate the phytotoxicity of flumioxazin on peanut, and in separate trials, the effects on peanut maturity. The first study evaluated time of flumioxazin application (0, 2, 4, 6, 8, and 10 d after planting [DAP]) and flumioxazin rate (nontreated, 71, and 105 g ai/ha). Peanut (variety ‘C99R’) were seeded 3.2 cm deep and irrigated immediately after seeding. Flumioxazin applied to peanut 6, 8, and 10 DAP significantly injured peanut (20 to 59%) early season, with more phytotoxicity from flumioxazin at 105 g/ha than 71 g/ha. However, peanut stand was not reduced by any of the times of application or rates. Peanut recovered by midseason, except in cases of severe (up to 49%) visual phytotoxic injury. Peanut yields were not affected by either flumioxazin application timing or rate. The second study (variety ‘Georgia Green’) evaluated flumioxazin applied at 105 g/ha at varying intervals after planting to determine the phytotoxic effects on peanut maturity using the hull-scrape method. Peanut maturity was delayed by flumioxazin when applied 1 d after planting and later. These results show that the optimum time of application is from immediately after planting to 2 d after planting, but ideally, the application should be made immediately after planting. The highest recommended flumioxazin rate, 105 g/ha, is not significantly phytotoxic when applied within the recommended range of timings and has no effect on yield. However, there is potential for yield loss as peanut maturity is delayed in cases of severe injury.