Our purpose was to investigate the influence of growth reserves of perennial range grasses on their tolerance to applications of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Competing annual grasses were removed with atrazine treatment at 1.1 kg/ha. The carbohydrate reserves of the perennial grasses were reduced by mowing the previous season. Crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] plants with reduced carbohydrate reserves, as indicated by reduced etiolated growth, were less tolerant to atrazine than their nonmowed counterparts. Without reduced carbohydrate reserves, squirreltail [Sitanion hystrix (Nutt.) J. G. Smith] was much more susceptible to atrazine than crested wheatgrass. Thus, the weed control treatment did not necessarily increase the density of desirable perennial grasses.

Field experiments were conducted during 1981 to 1984 to evaluate paraquat for weed control in alfalfa established for less than one year. Treatments were applied in March to alfalfa up to 4 cm tall and/or after cuttings to alfalfa up to 10 cm tall. Weeds were up to 20 cm tall. Paraquat applied in March controlled common chickweed and shepherd's-purse in some experiments. It did not control birdsrape mustard when applied after cuttings. Paraquat suppressed growth of perennial broadleaf weeds and grasses and reduced pressure from annual grasses in some experiments. March treatments generally did not increase, but sometimes decreased alfalfa yields. Paraquat applied after cuttings did not affect alfalfa yields in the majority of the experiments.

CGA 82725 {2-propynyl [2-[4-[(3,5-dichloro-2-pyridinyl)oxy)] phenoxy] propanoate}, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy]phenoxy] propanoic acid}, sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, and fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} were applied postemergence to Texas panicum (Panicum texanum Buckl. # PANTE), large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA], and broadleaf signalgrass [Brachiaria platyphylla (Griseb.)Nash. # BRAPP] in peanut (Arachis hypogaea L. ‘Florunner’). Fluazifop applied at 280 and 410 g ai/ha, sethoxydim at 340 g ai/ha, haloxyfop at 140 g ai/ha, and CGA 82725 at 280 g ai/ha usually gave better control when applied to annual grasses in the two- to four-leaf stage than when applied at the six- to eight-leaf stage. Higher rates of application were required to provide acceptable weed control at the later stage of growth. Peanut yields were usually higher following the early applications, indicating that timing of application is important in obtaining improved yields.

Field experiments were conducted at two locations in Virginia to evaluate the following herbicides: alachlor, diphenamid, diuron, metolachlor, napropamide, norflurazon, oryzalin, oxyfluorfen, paraquat, pendimethalin, and simazine. One experiment involved newly-transplanted apple trees; the others, three in apple and one in peach trees, involved one-year-old trees. Treatments were applied in the spring (mid-April to early-May). Control of annual weed species was excellent with several treatments. A broader spectrum of weeds was controlled in several instances when the preemergence herbicides were used in combinations. Perennial species, particularly broadleaf species and johnsongrass, were released when annual species were suppressed by the herbicides. A rye cover crop in nontreated plots suppressed the growth of weeds. New shoot growth of newly-transplanted apple trees was increased with 3 of 20 herbicide treatments and scion circumference was increased with 11 of 20 herbicide treatments compared to the nontreated control. Growth of one-year-old apple trees was not affected. Scion circumference of one-year-old peach trees was increased with 25 of 33 herbicide treatments.

Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] applied early enough for large crabgrass [Digitaria sanguinalis (L.) Scop.] control provided full season goosegrass [Eleusine indica (L.) Gaertn.] control during bermudagrass [Cynodon dactylon (L.) Pers. ‘Midiron’ and ‘Tufcoat’] establishment from sod strips. Prosulfalin {N-[[4-(dipropylamino)-3,5-dinitrophenyl]sulfonyl]-S,S-dimethylsulfilimine}, DCPA (dimethyl tetrachloroterephthalate), pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] and bensulide [0,0-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] gave full season goosegrass control in well-established Midiron bermudagrass, but not during the initial establishment period where open bare soil was present. Napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] provided long term residual control of goosegrass with some interference with rooting of bermudagrass from stolon nodes. Winter survival of Midiron bermudagrass was superior to Tufcoat bermudagrass. Controlling annual grasses permitted superior bermudagrass growth, and winter survival was improved tremendously. Postemergence goosegrass control was obtained with MSMA (monosodium methanearsonate) and methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] when repeated several times during the season. A mixture of MSMA and methazole was superior to either used alone. The rate of bermudagrass establishment was increased through the control of goosegrass with herbicides.

Rosering gaillardia (Gaillardia pulchella Foug. # GAIPU) and other herbaceous broadleaf plants were effectively controlled for one season by sprays of 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 1.1 kg ae/ha or glyphosate [N-(phosphonomethyl)glycine] at 1.1 kg ai/ha, or a 4:1 combination of 2,4-D and picloram (4-amino-3,5,6-trichloropicolinic acid) at 0.7 kg ae/ha applied in late March in the southern Rolling Plains of Texas. Production of perennial warm-season grasses increased 428, 480, 728, and 1440 kg/ha on a clay site 7 months after spraying with 2,4-D, 2,4-D plus picloram (4:1), atrazine [2-chloro-4-(ethylamino)-6-isopropylamino-s-triazine], and glyphosate, respectively. Application of 4.4 kg ae/ha of dalapon (2,2-dichloropropionic acid) severely damaged perennial warm-season grasses. Annual cool-season grasses were effectively controlled with sprays of atrazine or glyphosate at 1.1 kg ai/ha or dalapon at 4.4 kg ae/ha. Texas wintergrass (Stipa leucotricha Trin. & Rupr.) production was greatest on rangeland treated with 2,4-D or 2,4-D plus picloram (4:1).

Field, greenhouse, and laboratory studies were conducted to examine the potential for antagonism of postemergence graminicides when tank-mixed with cloransulam and to determine the role of herbicide absorption and translocation in observed antagonistic responses. Cloransulam antagonized annual grass control with aryloxyphenoxypropionate herbicides fluazifop-P, quizalofop, and the prepackaged formulation of fluazifop-P plus fenoxaprop. Cloransulam did not affect annual grass control with the cyclohexandiones clethodim and sethoxydim. In the greenhouse, increasing the rate of the graminicides was a more effective strategy for overcoming antagonism for quizalofop than for fluazifop-P or fluazifop-P plus fenoxaprop, and success was species dependent. Annual grass control with clethodim, sethoxydim, and glyphosate was not adversely affected by tank mixtures with cloransulam. Control of large rhizome johnsongrass was initially reduced when cloransulam was mixed with sethoxydim, fluazifop-P plus fenoxaprop, or quizalofop. By 6 wk after treatment, control of rhizome johnsongrass was antagonized only when cloransulam was mixed with sethoxydim. Rainfall within 1.5 h of application reduced johnsongrass control with glyphosate and sethoxydim but did not affect activity of the other herbicides. Absorption of 14C-fluazifop-P and 14C-quizalofop into broadleaf signalgrass was not affected by cloransulam 6 or 24 h after treatment. Translocation of 14C-fluazifop-P to broadleaf signalgrass shoot tissue above and below the treated leaf was decreased when fluazifop-P was combined with cloransulam. Translocation of quizalofop was not affected by cloransulam.

The need for practical revegetation strategies for managing medusahead-infested rangeland is substantial and unmet. Our objective was to test the potential for using the single-entry approach (simultaneous application of herbicide and seed with one entry) developed for other invasive-weed infested systems for revegetating medusahead-infested rangeland. Since areas infested with medusahead are frequently burned and burning may help control medusahead and provide a more suitable seedbed for desired species, we also tested the single-entry approach in conjunction with burning. Our primary hypotheses were that (1) the combination of imazapic and seeding would provide best establishment of desired species and (2) burning would enhance the efficacy of imazapic on medusahead and enhance seedling establishment. Treatments included three seeding rates (none, 13.2, or 25.0 kg ha−1 of an even mixture of all species), two herbicides (0 and 52 g a.i. ha−1 imazapic; with and without), and two burning regimes (burned, not burned) applied mid-October 2006 on two sites. In late July, 2008 through 2010, plant density and biomass were sampled. We found that the simultaneous application of imazapic and seeding resulted in establishment of desired species where they were absent. Imazapic application without seeding increased perennial bunchgrass density where enough residual plants existed before treatment. Burning tended to improve the control of medusahead with imazapic and promoted desired species. Even though follow-up treatments may be necessary, applying imazapic and seeding in a single-entry approach may provide a more practical initial revegetation strategy than multi-entry approaches on rangeland devoid of desired residual species. This procedure should reduce the costs of treatment application and make revegetating annual grass-infested rangeland more affordable.

A survey was conducted in 2000 across 38 counties in Mississippi on 192 randomly selected soybean fields to assess the most common occurring weeds. Statewide, prickly sida, which was present in 40% of the fields sampled, was the most common. Pitted and entireleaf morningglory were present in 34 and 29% of the soybean fields, respectively. Broadleaf signalgrass and barnyardgrass were the most common annual grasses, and yellow nutsedge was the most common sedge observed. Trumpetcreeper and redvine were the most common perennial vines. In the Mississippi Delta region of Mississippi, prickly sida was present in 45% of the fields sampled. The trend of occurrence of other species in the Delta mirrored statewide results. In eastern Mississippi, prickly sida and broadleaf signalgrass were found in 43% of soybean fields. Sicklepod, common cocklebur, and balloonvine were more prevalent in eastern Mississippi, when compared with the Mississippi Delta. Since 1982, there has been a sevenfold decline in the occurrence of common cocklebur and a fourfold decline in the occurrence of johnsongrass in Mississippi soybean. Also, the occurrences of redroot pigweed, common ragweed, and fall panicum have declined. Conversely, the occurrences of yellow nutsedge and broadleaf signalgrass have increased. The occurrences of barnyardgrass, prickly sida, redvine and trumpetcreeper have been relatively static over the past two decades.