Field trials were conducted to evaluate weed control and crop safety with postemergence-applied herbicides in two cultivars of low-tannin seedling sericea lespedeza (Lespedeza cuneata). Two applications of either 2,4-D amine at 0.28 kg ae/ha or 2,4-DB amine at 0.56 kg ae/ha controlled sicklepod (Senna obtusifolia) ≥ 90%. Equivalent control of smallflower morningglory (Jacquemontia tamnifolia) required either two applications of 2,4-D or three of 2,4-DB. Three applications of either herbicide were required for comparable spotted spurge (Euphorbia maculata) control. Sericea lespedeza was not adversely affected when either herbicide was applied up to three times per season over two consecutive seasons. Tolerance to 2,4-D and 2,4-DB was equal between two sericea lespedeza cultivars. Absorption of foliar-applied 14C-2,4-D was greater in sicklepod and smallflower morningglory than in sericea lespedeza. Translocation of absorbed 14C-2,4-D was equivalent between sicklepod and sericea lespedeza but greater in smallflower morningglory than in sericea lespedeza. Absorption and translocation of foliar-applied 14C-2,4-DB was equivalent between sicklepod and sericea lespedeza. Furthermore, 14C-2,4-DB absorption was less in smallflower morningglory than in sericea lespedeza.

The weed control spectrum of clomazone, the influence of clomazone on the performance of other herbicides, and the performance of tank mixtures containing clomazone were evaluated from 1985 through 1987. Clomazone applied preemergence at 280 g ai/ha controlled 90 to 100% of barnyardgrass, giant foxtail, goosegrass, large crabgrass, seedling johnsongrass, prickly sida, and velvetleaf. Clomazone at reduced rates was more effective applied preemergence than preplant-incorporated for 10 of 23 weed species. Clomazone enhanced imazaquin activity on entireleaf morningglory and sicklepod in 1986. A tank mixture of clomazone, imazaquin, and metribuzin at half the labeled rates reduced soybean injury, increased soybean yield, and controlled weeds as well as the mixture at labeled rates.

Greenhouse and field studies demonstrated that naptalam reduced paraquat activity by as much as 30% on sicklepod, smallflower morningglory, Florida beggarweed, and peanut Sequential application experiments, i.e. naptalam applied 2 or 24 h prior to an application of paraquat, as well as absorption studies utilizing 14C-paraquat, indicated that the antagonism was due largely to reduced paraquat absorption. Scanning electron microscopy revealed that application of naptalam, as well as naptalam applied with paraquat, resulted in amorphous deposits on the leaf surface which may account for the antagonism.

Field experiments were conducted in 1994 and 1995 to determine if the sodium salt of pyrithiobac or bromoxynil applied in a low-volume, air-assist spray system controlled entireleaf morningglory, pitted morningglory, and smallflower morningglory as well as treatments applied with a conventional hydraulic fan spraying system, and to determine if herbicide rates could be reduced when using the low-volume spraying system. Pyrithiobac at 0.035 and 0.071 kg ai/ha and bromoxynil at 0.56 and 1.12 kg ai/ha were applied alone and in combination with DSMA at 1.7 kg ai/ha or MSMA at 1.7 kg ai/ha. Spraying systems were calibrated to deliver 26 L/ha and 140 L/ha for the low-volume and conventional systems, respectively. No significant differences in control were noted between low-volume and conventional spray systems when herbicides were applied at the suggested use rates of 0.071 and 1.12 kg ai/ha for pyrithiobac and bromoxynil, respectively. Morningglory control was reduced when pyrithiobac and bromoxynil were applied at one-half the suggested use rate regardless of the spraying systems. Bromoxynil alone generally controlled pitted and entireleaf morningglory better than pyrithiobac alone regardless of rate and application method. However, pyrithiobac generally provided better control of smallflower morningglory than bromoxynil. Adding MSMA or DSMA to bromoxynil and pyrithiobac increased control of both weed species.

Freshly harvested smallflower morningglory [Jacquemontia tamnifolia (L.) Griseb. # IAQTA] seed germinated best after 25 to 60 s of scarification in an electric scarifier equipped with 100 to 120 grit emery cloth. Optimum temperature for germination was 25C. At 10 and 45C no germination occurred for up to 7 days. Eight and 12 days after planting in silt loam soil there was 85 and 98% emergence of smallflower morningglory from depths of 0.5 to 1 cm, whereas no emergence was observed from depths of 6 cm or greater 12 days after seeding.

Field studies were conducted from 1995 to 1997 near Tifton, GA, to determine the benefits of stale seedbed weed control in cucumber. Three stale seedbed management systems—(1) power till stale seedbeds twice (2 ×), (2) glyphosate application immediately after planting, and (3) combination system of stale seedbeds power tilled once 2 wk prior to planting followed by glyphosate application immediately after planting cucumber—were evaluated as main plots. Subplots were weed management systems after planting cucumber: intensive, basic, and cultivation alone. Weed densities were generally greater in 1996 and 1997 than in 1995. Yellow nutsedge was the overall predominant species in 1995 (46 plants m−2), with Florida pusley being the predominant species in 1996 and 1997, at 80 and 124 plants m−2, respectively. Generally, stale seedbeds shallow tilled 2 × had fewer weeds and greater cucumber yields than stale seedbeds treated with glyphosate. Glyphosate did not adequately control emerged Florida pusley on stale seedbeds, resulting in reduced cucumber yield. Clomazone preemergence and bentazon/halosulfuron postemergence were used for broadleaf weed control in the intensive weed management system. These herbicides injured cucumber plants, delayed maturity, and reduced yield. Based on our results, stale seedbeds shallow tilled 2 × can be integrated into cucumber production and provide effective cultural weed control. Furthermore, these systems will replace the need for potentially injurious herbicides.

Bentazon reduced paraquat phytotoxicity to Texas panicum, sicklepod, Florida beggarweed, and peanut. Bentazon applied alone had minimal effect on these species. Smallflower morningglory was more sensitive to bentazon than to paraquat; the interaction of paraquat and bentazon varied from antagonistic to synergistic depending upon the specific combination of rates. Antagonism with tank-mixed combinations was also obtained by applying bentazon prior to paraquat, but not with the reverse. Studies with 14C-labeled herbicides revealed that each herbicide inhibited foliar penetration of the other. In field studies, adding bentazon to paraquat reduced crop injury. However, except for smallflower morningglory, weed control was also reduced.

Field experiments were conducted in 1986, 1987, and 1988 to evaluate imazethapyr rate and time of application on postemergence control of 24 weed species. Contour graphs were developed that predicted imazethapyr rates required for various levels of weed control based upon weed leaf number at application. Rates below the labeled rate (70 g ha−1) provided 90% or greater control of common cocklebur, smallflower morningglory, and smooth pigweed if applied to 3 true-leaf or smaller weeds and of barnyardgrass, seedling johnsongrass, and Palmer amaranth if applied while weeds were in the cotyledon or 1 true-leaf stage. A rate of 70 g ha−1 provided 90% control of large crabgrass in the 1 true-leaf stage. Entireleaf morningglory, red rice, pitted morningglory, and velvetleaf are not susceptible enough to imazethapyr for 90% or greater control to be obtained with rates lower than 70 g ha−1 at the 1 true-leaf growth stage. These data demonstrate how control data can be used for developing effective reduced-rate herbicide recommendations based on weed leaf number.

Alachlor, chloramben, cinmethylin, diphenamid, fluazifop, fluazifop-P, metolachlor, metribuzin, napropamide, oryzalin, and sethoxydim were applied on transplanted sweet potato at Tifton, GA, during 1982 to 1985. The weeds most prevalent were large crabgrass, Florida pusley, smallflower morningglory, and yellow nutsedge. No significant phytotoxicity was observed from any herbicide treatment over the 4 yr. Cultivation at 4 wk is advantageous to eliminate early flushes of weeds which escape control and reform the beds. Alachlor or metolachlor at 4.5 and 3.4 kg ha-1, respectively, and metribuzin controlled weeds best. Although no serious phytotoxicity was evident, these treatments tended to cause lowered yields of marketable roots while marginally affecting total yields in most cases. Metribuzin was the only compound which controlled late-season broadleaf weeds such as smallflower morningglory effectively.

Field studies in 1990 and 1991 evaluated treatment timings of nicosulfuron and bentazon alone and in mixture for weed control, peanut injury, and yield. The experimental areas were treated with a broadcast PPI application of benefin at 1.68 kg ai ha-1. Nicosulfuron was applied at 40 g ai ha-1 and bentazon at 560 g ai ha-1. Nicosulfuron mixed with bentazon applied 1 wk after crop emergence (WAE) controlled yellow nutsedge 81%. Bentazon or bentazon plus nicosulfuron applied 1 or 3 WAE controlled smallflower morningglory at least 94%. Nicosulfuron controlled sicklepod at least 76% in 1990. However, control of sicklepod was 71% from 1 WAE nicosulfuron application in 1991 and less than 26% for 3, 5, or 7 WAE application. Bentazon controlled Ipomoea spp. at least 70% but did not control Florida beggarweed and sicklepod. Nicosulfuron alone controlled Florida beggarweed and Ipomoea spp. Nicosulfuron reduced early-season peanut growth, but peanut recovered by mid-August. Bentazon reduced nicosulfuron control of Florida beggarweed when applied 1, 3, or 5 WAE, but not 7 WAE. Bentazon mixed with nicosulfuron applied 3 WAE in 1990 reduced weed-free peanut yields compared to nicosulfuron alone. Nicosulfuron and bentazon did not significantly reduce peanut yields under weed-free conditions in 1991.

Interaction of glyphosate and 2,4-DB was evaluated in greenhouse and laboratory studies with respect to control of four species of annual morningglory. The greenhouse study included smallflower, pitted, palmleaf, and ivyleaf morningglory at three growth stages: seedling, juvenile, and vining. A series of glyphosate rates (0.28 to 1.26 kg ae/ha) and 2,4-DB (0.022 and 0.045 kg ae/ha) were applied alone, and in all possible two-way tank mixtures. Morningglory response to both glyphosate and 2,4-DB applied alone was species- and growth stage-dependent. All combinations were either additive or synergistic for control of pitted, palmleaf, and ivyleaf morningglory. Response of smallflower morningglory ranged from antagonistic to synergistic. Absorption and translocation of 14C-2,4-DB was independent of the addition of glyphosate in all four species. By contrast, absorption of foliar-applied 14C-glyphosate and translocation of 14C from treated leaves to other plant parts were enhanced by the addition of 2,4-DB in all species except palmleaf morningglory. In palmleaf morningglory, 14C-glyphosate absorption and translocation were independent of the addition of 2,4-DB. Absorption and translocation data were in agreement with greenhouse studies.

Field studies conducted at six locations in Georgia and one location in Virginia evaluated imazethapyr and imazethapyr mixtures for weed control, crop tolerance, and peanut yield. Imazethapyr applied early postemergence controlled bristly starbur, coffee senna, common cocklebur, Ipomoea species, jimsonweed, prickly sida, and smallflower morningglory at least 91% and controlled yellow and purple nutsedge 88 and 98%, respectively. Paraquat plus bentazon applied early postemergence did not control the aforementioned weeds as well as imazethapyr or imazethapyr mixtures. Paraquat applied with imazethapyr reduced bristly starbur control 15% compared to imazethapyr alone but did not influence control of the other species. Imazethapyr control of bristly starbur was not improved by the addition of bentazon. Sicklepod control was less than 24% with imazethapyr and was at least 58% with imazethapyr plus paraquat Imazethapyr plus paraquat controlled sicklepod better than paraquat plus bentazon at three of the four locations evaluated. Imazethapyr did not control Florida beggarweed, while imazethapyr plus paraquat controlled at least 53%. Peanut injury was minimal 30 d after application for all treatments.

The optimum pH for germination of smallflower morningglory (Jacquemontia tamnifolia (L.) Griseb. # IAQTA] seed was 8.0. A scarification time of 25 to 60 s using a drum scarifier with medium grit provided the best germination, and the optimum temperature for germination was 35 to 40C. However, the optimum temperature for growth was 25 to 35C, with reductions in growth occurring above or below this range. Emergence after 14 days was 81 and 49% at planting depths of 1.5 and 10 cm, respectively. Shade levels of 30 to 92% reduced smallflower morningglory growth by 38 to 87% compared to plants grown in full sunlight.

Experiments were conducted in 1991 and 1992 to evaluate the weed control effectiveness from several rates of AC 263,222 applied PPI and PRE (36 and 72 g ai/ha), early POST (EPOST) (18, 36, 54, or 72 g/ha), POST (18, 36, 54, or 72 g/ha), and EPOST followed by (fb) POST (27 fb 27 g/ha or 36 fb 36 g/ha). These treatments were compared to the commercial standard of bentazon at 0.28 kg ai/ha plus paraquat at 0.14 kg ai/ha EPOST fb bentazon at 0.56 kg/ha plus paraquat at 0.14 kg/ha plus 2,4-DB at 0.28 kg ae/ha. Application method had little effect on weed control with AC 263,222. In contrast, application rate affected control. Purple nutsedge, yellow nutsedge, prickly sida, smallflower morningglory, bristly starbur, common cocklebur, and coffee senna were controlled at least 82% with AC 263,222 at 36 g/ha (one-half the maximum registered use rate) regardless of application method. AC 263,222 at 72 g/ha (registered use rate) controlled sicklepod 84 to 93%, Florida beggarweed 65 to 100%, and Ipomoea morningglory species 89 to 99%. A single application of AC 263,222 at 36 g/ha or more controlled all weeds (with the exception of Florida beggarweed) as well or greater than sequential applications of bentazon plus paraquat fb bentazon, paraquat, and 2,4-DB. All rates of AC 263,222 applied POST and all application methods of AC 263,222 at 72 g/ha had better yields than the pendimethalin control.

Studies were conducted from 1990 through 1994 near Tifton, GA, on the population dynamics of yellow nutsedge and certain annual weeds in peanut—corn and peanut—cotton rotations. Converse rotation sequences were included to eliminate year effects. Continuous fallow plots (noncrop) were included for comparison. Within each crop, including fallow, were 3 levels of weed management: low, moderate, and intensive. Weed densities and numbers of yellow nutsedge tubers were not affected by crop rotations, but they were affected by individual crops and weed management systems in each crop. Fallow plots, including those with intensive fallow weed management using tillage and nonselective herbicides, consistently contained more yellow nutsedge plants and tubers than other plots. Moderate and intensive weed control systems in peanut and cotton reduced yellow nutsedge densities and tubers, but only peanut yields were increased by intensive weed management. Weed management systems did not affect yellow nutsedge densities in corn, although yields were increased by moderate and intensive systems due to improved control of other weeds. Our results suggest that uninterrupted plantings of peanut, corn, or cotton with moderate levels of weed management are generally sufficient to suppress yellow nutsedge and allow for optimum crop yield. If fields are fallow, yellow nutsedge population densities and tubers will increase exponentially, even with intensive fallow weed management.

Sulfentrazone was foliar applied at 34 and 56 g ai ha−1 alone or in combination with surfactants to soybean cultivars Hutcheson and Centennial and to sicklepod, coffee senna, smallflower morningglory, velvetleaf, and yellow nutsedge. The most sensitive weeds, including coffee senna, smallflower morningglory, and velvetleaf, were severely injured by the lowest rate when sulfentrazone was applied with surfactants. Sulfentrazone provided the highest control of yellow nutsedge with X-77. Soybeans were not severely injured by sulfentrazone applied alone, but 55% foliar injury occurred when the herbicide was applied with X-77. However, the seedlings were not killed. Sicklepod was the most tolerant of the weeds tested. In the absence of surfactants, the order of radiolabeled sulfentrazone absorption by the foliage was Centennial (5.8%) = Hutcheson (8.5%) = coffee senna (10.4%) < yellow nutsedge (17.0%) < velvetleaf (22.3%) = smallflower morningglory (24%). Sicklepod leaves did not retain droplets containing sulfentrazone when no surfactant was used. Species with the highest foliar absorption also showed the greatest phytotoxic response to the herbicide. Addition of surfactants to the spray mixture enhanced the foliar absorption and overall phytotoxicity of sulfentrazone in the weeds. An inverse relationship was detected between the foliar absorption of sulfentrazone without surfactants and the amount of cuticular wax present on the leaves. No such correlation was observed when surfactants were used. Thus, surfactants overcame the barrier to absorption imposed by the cuticular wax and, under these conditions, selectivity apparently became dependent upon species-specific cellular tolerance to sulfentrazone.

Field studies in 1990 and 1991 at six locations in Georgia and one location in North Carolina evaluated AC 263,222 for weed control, peanut tolerance, and yield. AC 263,222 applied early postemergence at 71 g ai ha−1 controlled bristly starbur, coffee senna, common lambsquarters, Ipomoea species, prickly sida, sicklepod, smallflower morningglory, and yellow nutsedge at least 91%. AC 263,222 controlled common cocklebur 77% and Florida beggarweed from 47 to 100%. Crop injury was 4% for AC 263,222 applied once and 12% or less from two applications. Mixtures of bentazon with AC 263,222 did not improve control compared to AC 263,222 alone. Imazethapyr did not improve control of AC 263,222 systems. In several locations, bentazon reduced control of Florida beggarweed with AC 263,222 when applied in a mixture compared to AC 263,222 alone. Weed control from the standard of paraquat plus bentazon applied early postemergence followed by paraquat, bentazon plus 2,4-DB applied POST did not provide the level or spectrum of weed control as AC 263,222 systems.

An experiment was conducted at two locations in Georgia and two locations in North Carolina during 1994 and 1995 to evaluate weed management in conventional-tillage bromoxynil-resistant Gossypium hirsutum L. (cotton). The weed management systems evaluated included different combinations of fluometuron preemergence (PRE), bromoxynil or bromoxynil plus MSMA early postemergence (EPOST), bromoxynil postemergence (POST), and cyanazine plus MSMA late post-directed (LAYBY). Fluometuron PRE improved control of Acanthospermum hisptdium DC. (bristly starbur), Cassia occidentalis L. (coffee senna), Chenopodium album L. (common lambsquarters), Desmodium tortuosum (Sw.) DC. (Florida beggarweed), Sida spinosa L. (prickly sida), Jacquemontia tamnifolia (L.) Griseb. (smallflower morningglory), and Anoda cristata (L.) Schlecht. (spurred anoda), compared to system that did not use fluometuron PRE. It also improved G. hirsutum yields at three four locations. Bromoxynil-containing systems provided better weed control and higher G. hirsutum yields than systems without bromoxynil. Bromoxynil EPOST controlled A. hispidium, C. occidentalis, C. album, D. tortuosum, S. spinosa, J. tamnifolia, and A. cristata. Control of these species was frequently improved by a second application of bromoxynil POST. Bromoxynil EPOST, POST, or EPOST plus POST did not control Senna obtusifolia (L.) Irwin and Barneby (sicklepod), but the addition of MSMA to bromoxynil EPOST improved S. obtusifolia control. Control of all dicotyledonous weeds was improved by a LAYBY treatment of cyanazine plus MSMA, and yields were improved at three of four locations with this treatment. Gossypium hirsutum was not injured by POST treatments of bromoxynil, and only temporary injury resulted from POST treatments of MSMA.

Research was conducted from 1978 through 1980 at Headland, AL, to evaluate the use of herbicides, mechanical cultivation, and hand-hoeing as components of a total weed control system for peanuts (Arachis hypogaea L.). Herbicides or two cultivations alone failed to provide acceptable weed control, peanut yields, or net returns for the 3-yr period. However, adding two cultivations to the herbicide treatments produced acceptable weed control, peanut yields, and net returns for the 3-yr period. Average peanut yield for herbicide(s) plus two cultivations was 3200 kg/ha with an average net return of $260/ha. Two cultivations plus two hoeings without herbicide(s) produced good results with an average 3-yr yield of 3380 kg/ha and a net return of $280/ha. Herbicide(s) plus two cultivation treatments that had net returns equal to two cultivations plus two hoeing treatments were: dinoseb (2-sec-butyl-4,6-dinitrophenol) at 5.0 kg ai/ha applied at ground-cracking ($300/ha); dinoseb + alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] at 1.7 + 3.4 kg ai/ha applied at ground-cracking ($310/ha); and alachlor at 4.5 kg/ha applied preemergence ($320/ha). Treatments containing herbicide(s) plus two cultivations plus two hoeings did not substantially improve weed control, peanut yields, or net returns over herbicide(s) plus two cultivations.

Field and laboratory investigations were conducted from 1983 through 1985 to evaluate morphological and environmental influences on the performance of imazaquin on 26 weed species common to the Mississippi Delta. Imazaquin applied preplant incorporated or preemergence at 140 g ai ha–1 controlled 16 species but controlled only five species at 140 g ha–1 foliar applied. Contour graphs accurately predicted imazaquin postemergence rates necessary to control a given weed species at a given time after emergence. Imazaquin applied preemergence with a sequential postemergence application controlled entireleaf morningglory and sicklepod better than a single soil application. Imazaquin at 140 g ha–1 applied preemergence required at least 50 mm of supplemental water following application to control sicklepod and was more phytotoxic to sicklepod grown at 25/10 C day/night temperatures than those grown at 32/22 C.