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Peanut injury in the field can occur from flumioxazin applied PRE, but this is associated with plants that have emerged, or are about to, emerge from soil. The direct effect of flumioxazin on peanut seed germination and radicle development has not been evaluated. Therefore, research was conducted to determine peanut seed radicle development response to flumioxazin at different concentrations (0.0, 0.01, 0.10, 1.0 and 10.0 ppb) when tested at multiple temperatures (20, 23, 26, and 29 C) in laboratory experiments on a thermogradient table. Data analysis indicated that flumioxazin concentration was not different from the nontreated control (0.0 ppb) for 0.01, 0.1, and 1.0 ppb for peanut germination. Flumioxazin at 10.0 ppb was different from all other treatments and the nontreated control. However, comparing linear regression models for each flumioxazin concentration across all temperatures indicated no differences for slope. These data indicate that when there is direct peanut seed exposure to flumioxazin at field application rates, there is no impact on germination and radicle development. Temperature was noted to affect radicle development greater than field application rates of flumioxazin. As temperature decreased, germination and radicle length was inhibited or decreased, respectively. Nomenclature: Flumioxazin, peanut, Arachis hypogaea (L.), radicle, seed germination

Peanut is an important oilseed crop and legume species, with more than 1.9 M tons produced annually in the U.S. Being indeterminate, peanut continually flowers and sets pods throughout the growing season, leading to the potential harvest of both mature and immature pods. To quantify the physiological impacts of peanut seed maturity, a two-year field study was conducted to elucidate the difference in canopy structure and reproductive characteristics, including flower production, yield, and grade between seed obtained from immature and mature seed of two commercial peanut cultivars: TUFRunner™ ‘727’ and FloRun™ ‘107’. Data indicated that seed from the yellow class of pods have lower vigor and overall plant development and performance; further, plants developed from immature seed never achieved a level of performance comparable to that of the mature brown/black pod classes. There were differences between cultivars in the severity of the impact of immaturity, with larger detrimental effects on immature TUFRunner™ ‘727’, which exhibited reduced emergence. Despite these cultivar differences, this study illustrated that mature seed performs better in a field setting than immature seed. These results are critically important to disproving the ‘catch-up' assumption: seed maturity not only has an impact on emergence, but on subsequent life history and performance traits through the remainder of the season.

Foliar application of nutrients is used by growers to remediate crop nutrient deficiencies, but anecdotal reports indicate there may be associated effects of accelerated crop maturity, particularly for irrigated peanut (Arachis hypogaea L.). Research was conducted to determine whether application of foliar fertilizers during early pod set could increase the proportion of early-maturing pods, and thereby increase the mature proportion of the profile under irrigated conditions. Field experiments were conducted in Florida at Citra in 2016, Jay in 2016 and 2017with a randomized complete block with four foliar fertilizer treatments, applied to GA-06G at R1 and again two wks later at R2. Treatments consisted of no foliar fertilizer (control), 10.0 kg N/ha, 1.0 kg P2O5/ha, and 0.34 kg B/ha at each application and two harvest timings. Harvest treatments were based on the adjusted growing degree d model for peanut and were timed to represent early and optimal crop maturity. Leaf tissue nutrient concentrations were determined from samples collected 24h after each foliar treatment application. Yield and proportion of mature pods were quantified after each digging date. Normalized difference vegetation index data showed no treatment differences. The maturity profile (percentage of mature pods present in the sample) was not consistently different from respective controls during either harvest period. Results indicate foliar fertilizer applied during flowering had little effect on maturity acceleration in peanut, though foliar fertilization may still be effective at alleviating in-season nutrient deficiencies. Within site-year, application of foliar fertilizer did not increase yield. Under sound soil fertility management programs, foliar fertilizers did not increase yield or the maturity profile of peanut.

Paraquat postemergence (POST) applied is often used to control broadleaf and grass weed species in peanut in the Southeast US. The objective of this study was to determine the effects of POST herbicide tank-mixtures including paraquat on vegetation, yield, and grade for runner-type peanut cultivars under irrigated and non-irrigated conditions. Two separate experiments (irrigated and non-irrigated) were conducted in 2016 and 2017 in Ty Ty and Plains Georgia. Georgia-06G, Georgia-14N, TUFRunner™ ‘511’, and FloRun™ ‘157’ cultivars were evaluated. Herbicide tank-mixtures included paraquat, paraquat plus acifluorfen plus bentazon, paraquat plus acifluorfen plus bentazon plus S-metolachlor, and paraquat plus acifluorfen plus bentazon plus acetochlor. Leaf burn, stunting injury, yield, and grade were evaluated. There were no interactions between herbicide and cultivar for all variables. Paraquat alone resulted in significantly greater foliar injury (3 DAT) than the other herbicide treatments for the irrigated (34 to 16%) and non-irrigated (28 to 15%) studies. Stunting for paraquat alone was noted at 15 and 35% for irrigated and non-irrigated, respectively. Similarly, in both studies, Georgia-06G and TUFRunner™ ‘511’ yielded 10 to 12% greater than Georgia-14N and FloRun™ ‘157’. Overall, the herbicide tank-mixtures did not have a negative effect on yield. With no interactions observed, these herbicide treatments can be used in conjunction with the given runner-type peanut cultivars in either irrigated or non-irrigated conditions without concern for excessive injury or decline in yield or grade.

Acetochlor, a chloroacetamide herbicide, is now registered for preplant (PPI), preemergence (PRE), and postemergence (POST) application in peanut. Field research was conducted during 2011 and 2012 in Georgia and North Carolina to determine peanut response and weed control by acetochlor compared with S-metolachlor alone and in programs with other herbicides. In weed-free experiments, peanut tolerance to acetochlor (1.26 and 2.52 kg ai/ha) and S-metolachlor (1.42 kg ai/ha) were evaluated when applied PPI, PRE, early postemergence (EPOST), or POST. Peanut tolerance to acetochlor was similar to S-metolachlor with no negative impact of either herbicide on peanut yield compared with non-treated peanut in absence of weed interference. When applied PRE, acetochlor controlled Palmer amaranth, pitted morningglory, sicklepod, and Texas millet similarly to S-metolachlor while control of broadleaf signalgrass was greater with S-metolachlor. Weed control programs containing EPOST and/or POST applications of herbicides following PRE herbicides provided the best overall weed control but did not affect yellow nutsedge control regardless of whether acetochlor or S-metolachlor were applied. Herbicide programs including PRE, EPOST, and POST herbicides most often resulted in the greatest yields. There was no difference in peanut yield regardless of the presence of acetochlor or S-metolachlor in a comprehensive herbicide program.

Calcium (Ca) availability in the 0 to 8 cm soil depth often limits peanut yield and influences grade in the southeastern United States. Field experiments were conducted in 2012 and 2013 at the University of Georgia's Coastal Plain Experiment Station, Tifton, GA (CPES) and the Southwest Georgia Research and Education Center, Plains, GA (SWREC) to determine large-seeded (Georgia-06G) and medium-seed sized (Georgia Greener) runner-type cultivar response to gypsum application rates of 0, 560, 1120, 1650 kg/ha. Peanut pod yield and grade (TSMK) were significantly different between locations with 7610 and 6540 kg/ha at CPES and SWREC, respectively. However, there were no differences between peanut cultivars or gypsum rates. Standard germination, seed vigor (cold germination), and seed Ca content analysis were also conducted on subsamples from each plot. Average peanut seed germination was 97% across all samples. No differences were observed for standard germination or vigor testing. Differences in locations were observed for yield, TSMK, percent jumbo, percent medium kernels, and seed Ca content. Peanut cultivar and gypsum application rate had effects on seed Ca concentration. Seed Ca concentration levels were 825 and 787 mg/kg for Georgia Greener and Georgia-06G, respectively. Seed Ca content increased as field gypsum application rate increased at both locations.

The development of 2,4-D-resistant cotton and soybean cultivars has created great concern about the potential off-target movement of 2,4-D onto sensitive broadleaf crops. Peanut is often grown in close proximity to cotton and soybean. Therefore, field studies were conducted during 2012 and 2013 at Plains, Ty Ty, and Attapulgus, GA to evaluate peanut response to 2,4-D at 67, 133, 266, 533, and 1066 g ae ha−1 applied at preemergence (PRE), 10, 20, or 30 d after planting (DAP), corresponding to PRE, V2, V3, and V5 peanut growth stages. Nontreated controls (NTC) were included for comparison. Treatment timing by rate interactions were significant (P < 0.0001). As 2,4-D rate increased peanut injury increased. There was variation in yield loss response dependent on peanut growth stage at application timing. Peanut that was treated preemergence and at the V2 growth stage did not have yield loss at any of the 2,4-D evaluated rates (67 to 1066 g ha−1) relative to the NTC. When peanut was treated at V3 and V5 growth stages with 2,4-D, injury estimates were 5 to 32% from the 67 to 1066 g ha−1 rates respectively, and peanut canopy diameter was stunted 5 to 35% at the same rates. The resulting peanut yield loss was 23 and 36% from 533 and 1066 g ha−1 of 2,4-D applied at V3 and V5 growth stages; in part due to reproductive growth being initiated during that time-frame and peanut had less time to recuperate before harvest. Linear regression models were used to evaluate peanut injury and peanut yield results. Significant correlations were established for V3 and V5 treatments between injury and yield, injury and canopy diameter, and canopy diameter and yield (P < 0.0001), with correlation coefficients of − 0.48, − 0.76, and 0.51, respectively. Growers and extension agents will be able to use these peanut injury estimates and canopy diameter data to make improved predictions of potential peanut yield loss where off-target movement of 2,4-D or sprayer contamination has occurred.

Determining an optimum harvest maturity for indeterminate crops such as peanut is critical because it directly affects yield and grade. Historically, the assumption has been that growers will harvest at optimum maturity due to the positive impact on these two characteristics. However, the increased acreage under management by a single farmer may cause growers to harvest prior to optimum maturity. The impact of peanut maturity on seed quality may not be fully understood by producers, where immature seed may have reduced emergence and vigor. Research was conducted to quantify the maturity of seed peanuts received by the Florida Foundation Seed Producers, Inc. (FFSP) at various stages of the shelling process: samples received from the field; after the in-shell samples were cleaned; after in-shell pre-sizing into two size classes; and after separation of in-shell samples at the gravity deck. Samples collected at each stage were pressure-washed to remove the exocarp and then separated into yellow and brown/black color classes based on the maturity board. Pods within each color class were counted, dried, weighed, and graded. Maturity at each sheller stage was assessed for three peanut cultivars. For the field stage, across all cultivars, 56% of pods were in the mature, or brown/black color class. This was well below the level of 70-80% in the brown/black class purported to be the maturity level that optimizes yield and grade. Cleaning had a minor impact on maturity percentages (average percent mature was 64% across all cultivars after passing through the mechanical cleaning process); however, in the pre-shelling sizing process where pods are sorted into “lead” and “small” baskets representing large and small pods, respectively, the maturity percentage was improved to 75% in the large pods and declined to 45% in the small pods. These results indicate that: 1) maturity levels of cultivars harvested in the field may not be optimal; and 2) that improvements could be made in maturity percentages by modifying the shelling process to separate the larger pods which are more likely to be mature than the smaller pods. These results also suggest that seed peanut lots are unlikely to be composed entirely of mature pods, that large numbers of immature pods could make it through the shelling process and that immature seed are planted by farmers. This could explain some cases of suboptimal plant stands in peanut.

Achieving and maintaining an adequate plant stand is a major priority when making planting and early season management decisions in peanut (Arachis hypogaea L.). Unpredictable and often extreme weather and high disease pressure in the southeastern United States can contribute to poor emergence and below-optimum plant stands. When plant stand is affected, replanting may be agronomically justified. This study was designed to determine i) the effect of plant stand on pod yield, market grade, and disease incidence in peanut seeded in a twin row pattern, (ii) if replanting is a viable option in a field with a below adequate stand and, iii) the best method for replanting peanut when an adequate stand is not achieved. Field trials were established at two locations in south Georgia in 2012 and 2013 to evaluate peanut production at four plant stands (7.4, 9.8, 12.3, and 14.8 plants/m [total plants/m across both units, or ‘twins' of the twin row pattern) and four replant methods (no replant, destroy the original stand and replant at a full seeding rate, add a reduced rate of seed to supplement the original stand with a single row between the original rows, and supplement with two additional rows with one between and the other next to the original rows). Replanting occurred when the stand had been established, an average of 24 days after initial planting. Pod yield at a stand of 12.3 plants/m was 6.6 and 5.8% greater than at a stand of 7.4 and 9.8 plants/m, respectively, with no benefit from increasing plant stand beyond 12.3 plants/m. Market grade was also maximized at 12.3 plants/m. Disease incidence was unaffected by plant stand. Yield was increased by supplementing an initial stand of 9.8 plants/m in both a single additional row and in two additional rows by 8.3 and 6.6%, respectively. A full replant of the original stand always resulted in lower yield, while grade was slightly increased in the full replant treatment. While an initial stand of 12.3 plants/m was needed in order to maintain yield potential, replanting via supplemental seed addition can recover lost yield at stands below this level.

The University of Georgia Extension recommendation for optimum plant stand in peanut (Arachis hypogaea L.) is 13.1 plants/m, although previous work has shown that yield potential can be maintained at lower plant stands. The unpredictable and often extreme weather and the ubiquity of pathogens in the region often contribute to poor emergence and poor plant stands. When plant stand is adversely affected, replanting the field may be a practical option. The objectives of this study were to determine i) the effect of plant stand on yield, grade and disease incidence, ii) at what plant stand peanut gains an advantage from replanting and iii) the best method for replanting peanut when an adequate stand is not achieved. Field trials took place in Plains, GA in 2011, 2012, and 2013; and Tifton, GA in 2012 and 2013 to evaluate peanut production at six plant stands (3.3, 4.9, 6.6, 8.2, 9.8, and 11.5 plants/m, in addition to a 13.1 plants/m control) in combination with three replant practices; i) no replant, ii) destroy the original stand and replant at a full seeding rate, and iii) add a reduced rate of seed to supplement the original stand) in a randomized complete block design. A positive linear trend for yield and a negative linear trend for tomato spotted wilt Tospovirus incidence were discovered as plant stand increased. Yield advantages from replanting occurred via supplemental seed addition to initial stands of 3.3 and 8.2 plants/m. Destroying the initial stand and completely replanting was never beneficial when compared to the other two replant practices. Replanting is warranted via supplemental seed addition at plant stands equal-to or below 8.2 plants/m.

Laboratory and greenhouse studies were conducted to determine the absorption, translocation, dose response, efficacy, and effects on biomass of the herbicide diclosulam on bristly starbur (Acanthospermum hispidum DC.) In laboratory experiments, 14C-diclosulam absorption and translocation was evaluated in bristly starbur. Greenhouse studies determined bristly starbur growth response to postemergence applied diclosulam at 0, 0.2, 0.4, 0.8, 1.6, 3.3, and 6.5 g ai/ha. Bristly starbur seed were collected from two Georgia locations, hand cleaned, and grown in the greenhouse. Bristly starbur plants were then foliar treated with diclosulam when plants were in the 4 to 6 leaf stage of growth. 14C-diclosulam was applied to a single non-treated, most fully developed bristly starbur adaxial leaf, after the rest of the plant was foliar treated with 0.8 g ai/ha of diclosulam. At 24 and 48 hours after treatment, 14C-diclosulam was translocated acropetally in bristly starbur to the plant apex, with little to no movement to the lower plant parts including lower leaves, stem and roots. For the dose response studies, bristly starbur growth reduction dry weight (GR50) and efficacy (I50) for diclosulam ranged from 0.95 to 0.92 g ai/ha, respectively. Based on these data, bristly starbur susceptibility to diclosulam was due to its translocation to apical growing points within 24 to 48 hours where acetoacetate synthase (ALS) inhibition occurred resulting in eventual plant death. While bristly starbur is controlled with diclosulam rates below the standard use rate of other weeds, the standard field rates in combination with other herbicide mechanisms of action will continue to be recommended to peanut growers to reduce the potential for bristly starbur ALS resistance selection.

Field studies were conducted at 13 locations across the US peanut belt during 2010–2012 to evaluate peanut response to postemergence applications of glufosinate. Glufosinate was applied at 0, 41, 82, 164, 328 and 656 g ai/ha 30, 60, and 90 days after planting (DAP). There was a significant interaction for peanut yield between application time and glufosinate rate; peanut yield data were regressed on rate of glufosinate and fit to a log-logistic dose response curve by application timing. At 30 DAP, peanut yield ranged from 16 to 92% of the non-treated control, with glufosinate at 266 g/ha causing an estimated 50% reduction in yield (Y50). At 60 DAP, peanut yield ranged from 16 to 82% of the nontreated control, with Y50 = 266 g/ha of glufosinate. Peanut yield when glufosinate was applied at 90 DAP ranged from 20 to 78% of the non-treated control; Y50 = 187 g/ha of glufosinate, which was lower than that at 30 DAP and indicated greater peanut sensitivity. Peanut plants treated at 30 DAP had more time to recover from glufosinate injury at the lower rates and/or were in a less susceptible stage of growth relative to 90 DAP. These data provide peanut growers across the US with an estimate of potential yield losses associated with mis-application, off-target movement, or sprayer contamination of glufosinate.

Field experiments were conducted at nine locations in Texas and Georgia in 2005 and 2006 to evaluate peanut tolerance to lactofen. Lactofen at 220 g ai/ha plus crop oil concentrate was applied to peanut at 6 leaf (lf), 6 lf followed by (fb) 15 days after the initial treatment (DAIT), 15 DAIT alone, 6 lf fb 30 DAIT, 30 DAIT alone, 6 lf fb 45 DAIT, 45 DAIT alone, 6 lf fb 60 DAIT, and 60 DAIT alone in weed-free plots. Lactofen caused visible leaf bronzing at all locations. Yield loss was observed when applications were made 45 DAIT, a timing that would correspond to plants in the R5 (beginning seed) to R6 (full seed) stage of growth. At all locations except the Texas High Plains, this application timing was within the 90 d preharvest interval. Growers who apply lactofen early in the peanut growing season to small weeds should have confidence that yields will not be negatively impacted despite dramatic above-ground injury symptoms; however, applications made later in the season, during seed fill, may adversely affect yield.

Due to limited hectares and production in comparison to field corn, soybean, and wheat, commercial research and development efforts by major manufacturers for potential new peanut herbicides are minimal. Therefore, new herbicides developed for large hectare crops should be evaluated for potential use in peanut. Field trials were conducted in Ty Ty and Plains Georgia in 2007 and 2008 to evaluate the tolerance of peanut to PRE and POST applications of pyroxasulfone at five rates (0, 120, 240, 360, and 480 g ai/ha). Pyroxasulfone did not cause significant peanut injury at the Ty Ty location. In Plains, PRE applications of pyroxasulfone caused significant crop stunting, particularly at the 360 and 480 g/ha rates. In Ty Ty, PRE applications of pyroxasulfone also resulted in greater expression of tomato spotted wilt virus than POST applications. Peanut yields were not reduced by any rate or timing of pyroxasulfone. These results suggest that pyroxasulfone may have some potential to be utilized in peanut.

Research was conducted at eight locations across the United States peanut belt during 2008 to evaluate peanut response to postemergence applications of dicamba. Dicamba was applied at 0, 40, 70, 140, 280 and 560 g ai/ha at 30, 60, and 90 days after peanut planting (DAP). In 5 of 8 locations, peanut yield losses were greater when dicamba was applied at 30 and 60 DAP when compared to 90 DAP. Estimated yield losses for dicamba applied at 40 g ai/ha ranged between 2% to 29%. Estimated yield losses for dicamba applied at 560 g ai/ha ranged between 23% to 100%. These data may aid peanut growers in making appropriate management decisions in situations where off-target movement of dicamba has occurred or sprayer contamination is suspected.

Most peanut (Arahcis hypogaea L.) production occurs under highly intensive conventional tillage systems. With recent volatility in input prices, reducing tillage trips is a viable way of reducing production costs. However, growers can experience yield loss when switching from conventional tillage to strip-tillage in peanut on certain soil types due to the lack of an elevated bed at harvest time. Studies were conducted to compare standard strip-till with strip-till on two-row raised beds as well as rip and beds prepared in the fall. Comparisons were made on a coarse textured soil at Tifton, GA and a fine textured soil at Plains, GA. The three bed types, with and without wheat cover, were evaluated over two years at both locations. No effects of cover or interactions with bed type were present. At Plains, the rip and bed and raised bed reduced digging losses by 62 and 47%, respectively. Soil compaction within the harvest depth was reduced by 3.3 and 4.7 times by the raised bed and rip and bed, respectively compared to flat strip-till. The rip and bed increased peanut yield by 465 kg ha−1 over flat bed. At Tifton, no significant differences in yield or digging losses occurred between tillage methods. Soil compaction in the harvest depth was reduced by 1.9 and 2.5 times by raised bed and rip and bed, respectively on this coarse soil type. Reduced compaction and digging losses along with increased yield suggest bedding is more important on finer textured soils.

Field experiments were conducted to evaluate the emergence and control of Florida beggarweed in peanut. Diclosulam preemergence (PRE), flumioxazin PRE, and imazapic postemergence (POST) were evaluated at three rates, along with paraquat plus bentazon plus 2,4-DB POST, and a nontreated control. These treatments were applied alone, or followed by chlorimuron applied late postemergence (LPOST). Variable Florida beggarweed control (16 to 90%) was observed when flumioxazin PRE, diclosulam PRE, paraquat plus bentazon plus 2,4-DB EPOST, or imazapic POST were applied alone. The pre-harvest population of Florida beggarweed was significantly reduced by the application of any residual herbicide (flumioxazin, diclosulam, or imazapic) alone at any rate either PRE or POST as compared to the nontreated control. Use of the contact treatment of paraquat plus bentazon plus 2,4-DB EPOST alone did not reduce Florida beggarweed populations as compared to the nontreated control. Adding chlorimuron LPOST to any treatment did not reduce Florida beggarweed populations, but provided suppression and reduced the biomass of existing plants. Consistent Florida beggarweed control (86 to 95%) was achieved with combinations of flumioxazin PRE at 105 g ha−1, diclosulam PRE at 53 g ha−1, and imazapic POST at 71 g ha−1 followed by chlorimuron LPOST at 9 g ha−1. The benefit of chlorimuron LPOST was greatest when early season control was least.

Greenhouse experiments were conducted to determine the effect of soil type, residual herbicide, and herbicide rate on peanut seedling development. Diclosulam, flumioxazin, and sulfentrazon...

Field studies were conducted in Alabama and Georgia in 2002 and 2003 to determine whether the peanut cultivar that replaced the cultivar Florunner can tolerate earlier applications of the herbicide chlorimuron than what is registered. The application timing restriction of chlorimuron on peanut had been established in the late 1980s with Florunner. In a factorial treatment arrangement, the cultivars AT201, Georgia Green, Viragard, C99R, and Florunner were treated with chlorimuron at 8.75 g ai/ha at 5, 7, 9, or 11 wk after planting. Only the later two application timings are covered by the current registration. Across all 4 yr-location replications, yield was influenced by the main effect of peanut cultivar. C99R was consistently the highest yielding cultivar. Chlorimuron had no effect on yield, regardless of application timing when compared to the nontreated entries in three of the four repetitions (i.e. Plains 2002, Plains 2003, and Headland 2002). Cultivar-based chlorimuron tolerance differences were detected only at Headland in 2003. For this location, chlorimuron applied at 5 wk after planting reduced yield across all cultivars, while application at 7, 9, and 11 WAP had no effect on yield. Results indicate that chlorimuron possesses a yield-reducing risk only when the crop has been stressed by other factors. Assuming that the crop has been stressed, the potential of yield reduction can be avoided only by observing the currently registered application timing. No clear indication was obtained that one cultivar was more tolerant to chlorimuron than another cultivar.

Imazapic, diclosulam, and flumioxazin have been registered for use in peanut since 1996. These herbicides provide substantial residual control of broadleaf weeds in peanut. A comprehensive review was conducted for these residual herbicides to determine their role in future weed control systems in peanuts. Weed control data for research from over 100 experiments conducted from 1990–2000 by Georgia, Florida, and Auburn Universities and USDA-ARS scientists were compiled. Residual herbicide systems evaluated were imazapic postemergence (POST) at 71 g ai/ha, flumioxazin preemergence (PRE) at 70, 87, and 104 g ai/ha, diclosulam preplant incorporated (PPI) and PRE at 18 and 26 g ai/ha, and paraquat plus bentazon early POST (EPOST). Other treatments included the residual herbicides used in combination with paraquat plus bentazon EPOST, for a total of 17 treatments. Regionally important weeds were selected and included: sicklepod, Florida beggarweed, purple and yellow nut-sedge, Ipomoea morningglory species, and smallflower morningglory. Sicklepod control with imazapic alone was 86% (50 tests), 73% (25 tests) with paraquat plus bentazon, and 63% or less with diclosulam and flumioxazin regardless of rate. Florida beggarweed control was 90% (29 tests) with flumioxazin (104 g/ha PRE); 78% (50 tests) with diclosulam 26 g/ha PPI; 72% (72 tests) with imazapic; and 70% (40 tests) with paraquat plus bentazon. Purple and yellow nutsedge control was 90% with imazapic. Yellow nutsedge control was 78% (18 tests) with diclosulam (26 g/ha PRE) and less than 69% with flumioxazin and paraquat plus bentazon. Paraquat plus bentazon increased weed control over residual herbicides alone.

Field trials were conducted in Georgia, North Carolina, and Texas to evaluate the effects of preplant applications of 2,4-D, dicamba, tribenuron, and tribenuron plus thifensulfuron on peanut yield. Herbicides were applied 30, 15, 7, or 0 d before planting (DBP) in conventional production systems in Georgia and Texas, and 28, 21, 14, 7, and 0 DBP in no- and strip-tillage systems in North Carolina. Amine and ester formulations of 2,4-D did not affect peanut yield at any time of application in any state. Dicamba reduced peanut yield when applied at 0 DBP in two of seven trials. Tribenuron did not affect peanut yield regardless of preplant interval. However, tribenuron plus thifensulfuron reduced yields when applied at 7 DBP in one of five trials. These data suggest that 2,4-D, tribenuron, and tribenuron plus thifensulfuron can be safely used for preplant weed control in peanut when applied 7 DBP. Dicamba should be applied a minimum of 15 DBP.

Field studies were conducted during 1997 and 1998 at three different locations in Georgia to determine peanut and weed response to pendimethalin at 1.1 kg ai/ha applied preplantincorporated (PPI) followed by flumioxazin at 71, 87, and 105 g ai/ha applied preemergence (PRE). Other residual treatments combinations with pendimethalin PPI included flumioxazin mixed with metolachlor or dimethenamid PRE, diclosulam PRE, norflurazon PRE, and imazapic applied postemergence (POST). Herbicide combinations that included flumioxazin controlled Florida beggarweed, tropic croton, and small flower morningglory at least 78% or greater. Late season Florida beggarweed control was 90% or greater with pendimethalin PPI plus flumioxazin at 87 to 105 g/ha applied PRE. Pendimethalin plus flumioxazin did not control sicklepod or yellow nutsedge. Smallflower morningglory control with all herbicide treatments was 90% or greater. Entireleaf morningglory control (when used in combination with pendimethalin PPI) increased from 80% with flumioxazin at 105 g/ha to 90% for flumioxazin in combination with metolachlor. Yields were similar for flumioxazin, norflurazon, imazapic, and diclosulam treated peanut.

Field studies were conducted from 1996 to 1998 in Georgia to determine peanut (Arachis hypogaea L.) and weed response to ethalfluralin (0.8 kg ai/ha) plus diclosulam applied preplant incorporated (PPI) at 9, 18, 26, 35 and 52 g ai/ha. Other treatments included ethalfluralin PPI followed by paraquat plus bentazon (140 and 280 g ai/ha, respectively) early postemergence (EPOST) applied alone or following ethalfluralin plus diclosulam (18 and 26 g ai/ha) PPI, ethalfluralin PPI followed by imazapic (71 g ai/ha) postemergence (POST), and ethalfluralin PPI. Ethalfluralin was applied PPI in all herbicide programs. Diclosulam controlled Florida beggarweed [Desmodium tortuosum (Sweet) D.C.], sicklepod [Senna obtusifolia (L.) Irwin and Barneby], and yellow nutsedge (Cyperus esculentus L.) inconsistently, and POST application of paraquat plus bentazon was needed for acceptable control. However, diclosulam controlled common ragweed (Ambrosia artemisiifolia L.), tropic croton (Croton glandulosus Muell-Arg.), wild poinsettia (Euphorbia heterophylla L.), and prickly sida (Sida spinosa L.) without the need for POST herbicides. Higher yields were recorded with diclosulam PPI followed by a sequential application of paraquat plus bentazon than herbicide programs not containing diclosulam or diclosulam alone. Diclosulam PPI followed by sequential applications of paraquat plus bentazon provided greater control of sicklepod and prickly sida that resulted in greater yields. Yields from dicosulam PPI followed by paraquat plus bentazon EPOST were equivalent to yields with paraquat plus bentazon EPOST followed by imazapic POST or imazapic EPOST.

The development of dicamba-resistant cotton and soybean cultivars has created great concern about the potential off-target movement of dicamba onto sensitive broadleaf crops. Peanut is often grown in close proximity to cotton and soybean. Therefore, field studies were conducted during 2012 and 2013 at Plains, Ty Ty, and Attapulgus, GA to evaluate peanut response to dicamba rates 35, 70, 140, 280, and 560 g ae ha-1 applied at preemergence (PRE), 10, 20, or 30 d after planting (DAP) corresponding to PRE, V2, V3, and V5 peanut growth stages, respectively. Nontreated controls were included for comparison. Location by rate (P < 0.0002) and location by treatment timing (P < 0.004) interactions were significant. As dicamba rate increased peanut injury and yield loss increased. There was variation in peanut response by location after PRE treatments. Plains peanut was injured less among locations, possibly due to the Greenville soil there having higher organic matter and clay contents at 3.8 and 30%, resp...