Chlorsulfuron [2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-amino] carbonyl] benzenesulfonamide], applied at 9 to 560 g ai/ha to the soil surface, stopped shoot elongation of well established Canada thistle [Cirsium arvense (L.) Scop. #4 CIRAR] plants in the greenhouse. Root fresh weight decreased progressively as chlorsulfuron rate was increased when measured 1 month after treatment. In contrast, the number of visible root buds plus secondary shoots increased 1.9- to 2.3-fold between 9 and 67 g/ha chlorsulfuron 1 month after soil surface treatment. Despite more numerous root buds, the number of secondary shoots arising from adventitious root buds progressively decreased as chlorsulfuron rate was raised. Increases in the number of visible root buds were observed first between 3 and 4 weeks following soil application with 67 g/ha of chlorsulfuron, 2 weeks after shoot growth stopped.

Field studies were conducted at Tifton, GA to quantify phytotoxicity of flumetsulam on peanut as influenced by application rate and timing in a weed free experiment. Flumetsulam PPI at rates up to 0.14 kg ai/ha visibly injured peanut and reduced canopy width, but injury from PPI flumetsulam at 0.07 kg/ha or less was no worse than a standard early postemergence (EPOST) treatment of bentazon (0.6 kg ai/ha) plus paraquat (0.14 kg ai/ha). Flumetsulam EPOST at rates up to 0.07 kg/ha visibly injured peanut and reduced peanut canopy width. Flumetsulam injury at rates of 0.035 kg/ha EPOST was similar to that caused by bentazon plus paraquat. Interactive effects of PPI and EPOST flumetsulam reduced early and mid-season pod and foliage biomass more than either application alone. However, peanut recovered with final yields not affected by flumetsulam, regardless of rate or time of application.

Herbicides may be exposed to a broad range of anaerobic conditions in the environment. This range can extend from weakly reducing conditions within typically aerobic compartments to stable, strongly reducing conditions in sites well removed from oxidative conditions. Currently, Federal Insecticide Fungicide and Rodenticide Act (FIFRA) regulatory guidelines specify the design criteria for guideline studies that frequently result in highly stable, strongly reducing test systems. These test systems do not simulate environments where herbicides are likely to occur. Design criteria for anaerobic aquatic test systems can influence the nature of the results of anaerobic aquatic metabolism studies as well as the relevance of these results to natural environmental processes. Design criteria which should be considered are the effects of sediment to water ratio, establishment of an anaerobic system, monitoring the reducing potential (Eh) of the system and the system Eh-pH relationship. These criteria influence how results are interpreted and the extrapolation of data to field environments where herbicides are likely to occur.

Oil-water emulsion stability was determined for crop origin and refinement of seed oils and their methyl esterified fatty acids (methylated seed oil) as influenced by emulsifiers and herbicides. Oil-in-water emulsion stability of one-refined, degummed, and crude seed oils was affected by the emulsifier. However, emulsion stability of methylated seed oil was not affected by the refinement of the seed oil used to produce the methylated seed oil or by the emulsifier. Oils without emulsifiers or emulsifiers alone added to formulated herbicide-water emulsions reduced emulsion stability depending upon the herbicide and emulsifier. Further, emulsion stability of formulated herbicides plus oil adjuvants was influenced by the oil type, the emulsifier in the oil adjuvant, and the herbicide. Oil-in-water emulsions improved or were not affected by increasing concentration of the emulsifier in the oil. However, T-Mulz-VO at a concentration greater than 10% with soybean oil or 5% with methylated soybean oil reduced emulsion stability with sethoxydim. Emulsion stability of herbicides with adjuvants depends upon the herbicide, the emulsifier, emulsifier concentration, and the crop origin, type, and refinement of oil.

In 1986 and 1987, imazethapyr at 0.11 or 0.14 kg ai/ha and metolachlor plus imazaquin at 1.4 plus 0.16 kg/ha, applied preplant incorporated, controlled greater than 85% of red rice in soybeans. Red rice was controlled similarly by standard herbicide treatments of alachlor at 2.8 kg ai/ha, metolachlor at 2.2 kg ai/ha, and alachlor plus imazaquin at 2.5 plus 0.14 kg ai/ha. Eighty-four percent or more of red rice was controlled with single postemergence herbicide treatments of DPX-Y6202-31 at 0.14 kg ai/ha or imazethapyr at 0.11 kg ai/ha or by sequential postemergence treatment of DPX-Y6202-31 (0.07 plus 0.07 kg ai/ha) or clethodim (0.1 plus 0.1 kg ai/ha). Soybean injury was insignificant, and yields from treated plots were superior or equal to those from untreated plots.

The tolerance of canola and wild mustard to postemergence HOE 075032 was investigated in greenhouse and field studies. In the greenhouse, the tolerance of canola to HOE 075032 applied at the 2 Ho 3-leaf stage was approximately twice the tolerance of wild mustard. In the field, HOE 075032 applied at 5 and 10 g ai/ha at the 2 to 3-leaf stage reduced wild mustard plant density and fresh weight by over 95%. Wild mustard contamination in canola seed was reduced from 45 to less than 1%. Application of HOE 075032 at 5 g/ha significantly increased canola yield and fresh weight in each year. Canola yield increases of 25, 139, and 86% were observed for the 5 g/ha treatment in 1991, 1992, and 1993, respectively. HOE 075032 could provide a postemergent alternative to the existing herbicide for wild mustard control in canola.

Field studies were established to evaluate several herbicides for buckbrush control in tall fescue pastures. Buckbrush was controlled most consistently by 2,4-D amine or low volatile ester, or package-mixes of 2,4-D plus dicamba or triclopyr. Two consecutive years of herbicide application was more effective for reducing buckbrush stem populations than one application.

Recent advances in genetic engineering have led to the development of glyphosate-resistant (GR) crops for genetic markers and selective weed control. The effects of glyphosate residue on turfgrass clippings could be toxic to non-GR species. The objective of this experiment was to determine whether glyphosate would retain activity within clippings of creeping bentgrass when applied to Kentucky bluegrass and perennial ryegrass. Greenhouse-grown ‘Penncross’ and GR ‘ASR-368’ were treated with glyphosate at 2.24 kg/ha. Clippings were collected 1, 3, 7, and 12 d after application and applied to greenhouse-grown Kentucky bluegrass and perennial ryegrass. Kentucky bluegrass and perennial ryegrass dry weight and percent cover were reduced by clippings receiving glyphosate that were harvested 1 and 3 d after glyphosate application from both susceptible and resistant creeping bentgrass. Results indicate that glyphosate remains active in clippings for up to 3 d after treatment within creeping bentgrass clippings. Glyphosate-applied creeping bentgrass clippings will need to be managed to prevent injury to susceptible species.

Two field experiments were conducted to evaluate the reduction of torpedograss canopy by multiple split applications of quinclorac applied postemergence (POST) to bermudagrass golf course roughs in Florida. In one experiment, quinclorac treatments were reapplied for a second year to the same plots, followed by biomass harvest, to evaluate the reduction of torpedograss rhizomes. Quinclorac sprayed at 1.68 kg/ha/yr visually reduced torpedograss canopy to a varying extent, depending on the number of split applications. The most effective treatment, 0.42 kg/ha quinclorac applied four times each year for 2 yr, reduced torpedograss canopy to 10% compared with 86% torpedograss canopy in the untreated plots, and reduced torpedograss dry weight to 1,570 kg/ha compared with 8,010 kg/ha in the untreated plots. After reapplication for 2 yr with the commercially labeled treatment, quinclorac at 0.84 kg/ha applied twice per year, torpedograss canopy was reduced to 45% and dry weight to 4,640 kg/ha. Visual evaluation of canopy was too optimistic in representing the herbicidal control of torpedograss by quinclorac because torpedograss regrew from rhizomes, and canopy was a relatively small part of the plant. In plots not chemically treated, pachymorph rhizomes were 63%, leptomorph rhizomes were 24%, and leaves were only 13% of the total dry weight of torpedograss.

Control of goosegrass and large crabgrass with different preemergence herbicides for the initial and sequential application was studied at four locations in Indiana. Pendimethalin at 1.1 kg ai ha-1 was used as the initial application in all treatments. Sequential treatments applied 6 wk after the initial treatment consisted of: 2.2 kg ha-1 benefin; 1.4/0.7 kg ha-1 benefin/trifluralin; 8.4 kg ha-1 bensulide; 11.8 kg ha-1 DCPA; 0.6 kg ha-1 dithiopyr; 2.2 kg ha-1 oxadiazon; 1.1 kg ha-1 pendimethalin; or 0.6 kg ha-1 prodiamine. Dithiopyr at 0.6 kg ha-1 with no initial application was also included. Highest large crabgrass control ratings were obtained through September with pendimethalin + pendimethalin, pendimethalin + dithiopyr, and dithiopyr alone postemergence. All other sequential applications tested improved control over a single application of 1.1 kg ha-1 pendimethalin, but rarely gave adequate season long control.

The regulation of transgenic plants is at the very early stages of dialog between the U.S. Environmental Protection Agency (EPA), the Food and Drug Administration (FDA), and the U.S. Department of Agriculture (USDA). Herbicide resistance is discussed in the broader terms of resistance management and of the cooperative efforts underway involving governments, industry, academia, and the environmental community on an international level. A new body, the International Organization for Resistant Pest Management (IOPRM) was formed to implement pesticide resistance management programs worldwide. The research base for integrated pest management programs which form the context for pesticide resistance management programs is in need of expansion. Public and private efforts to expand this base converge in an ambitious collaborative program between the U.S. EPA and USDA entitled the National Integrated Pest Management Forum. Finally, the potential role of EPA in the regulation of resistance management is discussed.

Field studies to evaluate the response of cotton to flame cultivation were conducted in 1994, 1995, and 1996. Flame cultivation at different liquid propane-gas (LP-gas) pressure settings (100 and 175 kPa) with or without watershield protection was applied to cotton at two stages of growth (20 to 25 cm and 40 to 45 cm tall). In 1994, younger cotton was more susceptible to flame cultivation than older cotton, and flaming at an LP-gas pressure of 175 kPa without watershield protection increased plant injury regardless of growth stage, whereas injury was not evident in 1995 and 1996. Injury caused by flame cultivation was a transient browning of lower leaf margins. The use of a watershield sprayed above the burner reduced injury. Flame cultivation applied to cotton 20 to 25 cm tall slightly elevated the first fruiting node, but no effects were noted on other vegetative and reproductive growth parameters or yield regardless of pressure setting or watershield protection. Flame cultivation applied to cotton 40 to 45 cm tall did not affect the position of the first fruiting node. Although flame cultivation caused some injury one year, total seed cotton and cotton lint yields were not reduced.

Experiments were conducted from 1987 through 1989 to determine the most effective and consistent control of velvetleaf in cotton with soil-applied herbicides. Norflurazon was applied at 1.1 or 1.7 kg ha-1 either preplant (PPI) or preemergence (PRE) or by splitting these rates and applying half PPI and the other half PRE. All methods of norflurazon application were compared with and without a PRE application of diuron at 1.1 kg ha-1. The most consistent control was achieved with PPI norflurazon at either 1.1 or 1.7 kg ha-1 followed by diuron. In 1988, crop injury at 2 wk varied and was 29% or greater for preemergence norflurazon tank-mixed with diuron.

Field experiments were conducted to evaluate the effect of application time on common waterplantain control in wild rice with MCPA and 2,4-D. Common waterplantain control was greatest when MCPA or 2,4-D were applied at 1.1 or 1.7 kg ai/ha at the two-aerial leaf stage. The best late-season control was MCPA applied at the scape elongation growth stage. Common waterplantain was controlled adequately when 0.6 to 0.8 kg/ha of MCPA were applied at the scape elongation or early flowering stage. However, because of common water plantain interference and sensitivity of wild rice to late herbicide applications, the best treatment stage for wild rice yield was when MCPA was applied at 0.6 kg/ha to common waterplantain at the two-aerial leaf stage. Wild rice at this time is at the more tolerant one-aerial leaf growth stage.

An educational software program was developed to demonstrate the interactions among weed population demographic processes, plant community interactions, and grassland noxious weed management options. The software includes an example model parameterized to simulate yellow starthistle population dynamics and graphic output. The software allows students to change weed and competing grass population demographic parameters, herbicide, and biological control management options. The graphic output allows the user to observe the outcome of integration of weed biology and various weed management options.

Field studies were conducted in 2002 and 2003 to determine the effects of herbicides applied below suggested use rates on weed management, yield, and estimated net return of peanut in both narrow and wide row-spacing regimes. In the single row-spacing regime study, diclosulam at 6 g/ha (1/4×) (1/4 labeled use rate) plus flumioxazin at 26 g/ha (1/4×) applied PRE followed by (fb) imazapic POST at 17, (1/4×), 35, (1/2×), or 70, (1×) g/ha was the lowest herbicide input that provided at least 80% control of sicklepod, yellow nutsedge, Florida beggarweed, and hairy indigo at 21 d after treatment (DAT). By 42 DAT, weed control was ≥ 80%, similar to herbicide treatments applied at labeled rates. In the twin row-spacing regime study at Jay, FL, and Citra, FL, in 2003, yellow nutsedge control was lowest (83 to 85%) from diclosulam applied at 1/4× in combination with flumioxazin at 1/4× PRE and flumioxazin at 1/4× or 52 g/ha (1/2×) PRE alone. All other herbicide treatments provided > 90% control. Diclosulam at 13 g/ha (1/2×) fb imazapic at 1/2× and flumioxazin at 1/4× fb imazapic at 1/2× was the lowest rate combination that provided > 80% control of sicklepod. Florida beggarweed control was > 90% with all rate combinations except diclosulam PRE alone, diclosulam at 1/4× PRE fb imazapic at 1/4× POST, and imazapic at 1/4× alone POST. Net return in the single-row spacing regime was highest for flumioxazin at 105 g/ha (1×) PRE alone, diclosulam at 1/4× applied with flumioxazin at 1/4× PRE alone or fb imazapic at 1× ($1,114, $1,094, and $990/ha, respectively). The twin row-spacing regime net return was highest with diclosulam PRE alone at 1/4, 1/2, or 26 g/ha (1×) ($2,063, $1,846, $1,734/ha, respectively). Diclosulam applied with flumioxazin at 1/2× fb imazapic at 1/2× was the lowest herbicide tank-mix input providing high net return at $1,162/ha.

Broadleaf weed control with postemergence applications of CGA-248757 and flumiclorac applied alone and in tank mixtures was evaluated in greenhouse and field studies. In greenhouse studies velvetleaf, common lambsquarters, redroot pigweed, common ragweed, common cocklebur, eastern black nightshade, and wild mustard shoot weight were reduced by 50% from 0.1, 2.9, 0.9, 1.1, 0.8, 0.4, and 1.2 g/ha of CGA-248757 and 0.7, 3.0, 2.4, 3.3, 3.0, 3.4, and 74.1 g/ha of flumiclorac, respectively. Under greenhouse conditions, tank mixtures of CGA-248757 or flumiclorac with atrazine, bentazon, bromoxynil, dicamba, halosulfuron, imazethapyr, lactofen, primisulfuron plus prosulfuron, or 2,4-D increased velvetleaf, common lambsquarters, redroot pigweed, or common ragweed control 14 d after treatment (DAT) when compared with the control provided by atrazine, bentazon, bromoxynil, dicamba, halosulfuron, imazethapyr, lactofen, primisulfuron plus prosulfuron, or 2,4-D applied alone. In field studies, adding CGA-248757 or flumiclorac to atrazine, bentazon, bromoxynil, dicamba, halosulfuron, imazethapyr, lactofen, CGA-277476, primisulfuron plus prosulfuron, or 2,4-D increased crop injury 3 DAT, but there was no reduction in corn or soybean yields as a result. In corn, tank mixtures of CGA-248757 or flumiclorac plus atrazine, dicamba, or 2,4-D increased velvetleaf control compared with treatments without CGA-248757 or flumiclorac. Tank mixtures of CGA-248757 or flumiclorac with primisulfuron plus prosulfuron increased common lambsquarters control compared with primisulfuron plus prosulfuron alone. Similarly, in soybean CGA-248757 or flumiclorac tank mixtures with bentazon or CGA-277476 increased control of redroot pigweed, and tank mixtures with lactofen increased common lambsquarters control. However, season-long broadleaf control in soybean with bentazon, lactofen, and CGA-277476 tank mixtures with CGA-248757 or flumiclorac did not provide acceptable weed control. Compared with imazethapyr alone the addition of CGA-248757 and flumiclorac improved soybean yield and provided season-long eastern black nightshade, common lambsquarters, redroot pigweed, and common ragweed control.

Two or three applications of MSMA applied alone were ineffective in controlling smutgrass in common bermudagrass turf. Where atrazine at 2.2 kg ai/ha or simazine at 2.2 kg/ha was followed by two or three MSMA applications at 2.2 or 4.5 kg/ha, smutgrass control was increased. Metribuzin followed by two or three applications of MSMA was only slightly better than MSMA applied alone. Up to 35% injury to bermudagrass was observed 2 wk after the initial MSMA or the MSMA-triazine treatment, but complete recovery was evident 2 to 4 wk later, even with one or two follow-up MSMA applications at weekly intervals. Bermudagrass injury from the application of triazines followed with MSMA did not differ from MSMA applied alone in two of three experiments. In one experiment, atrazine or metribuzin followed with MSMA applications caused 10 to 25% more bermudagrass injury than MSMA applied alone.

Plantain, which weary toilers dig from their lawns, hoe from their gardens, or cultivate from their fields was brought to the United States to serve man. Originally considered a valuable medicinal herb and an edible green, it was grown in monastery gardens and was cultivated in botanic gardens. It still is raised as a crop for bird feed.

Three experiments were conducted in the field using common cocklebur as a test species to identify weed growth differences due to propagation method and weed age when transplanted (with no crop and with soybean). Two experiments involved weed establishment in noncrop areas using four propagation methods (direct seeded–transplanted, peat tablets, peat pots, and plastic inserts) in a factorial arrangement with three transplant timings (at the cotyledon stage, at two true leaves, and at four true leaves). A direct-seeded method was also included as a check. Propagation methods and transplant timings were contrasted to the direct-seeded method because it was the “most natural” method of those tested. Based on results from the first year, the peat tablet method at the three transplant timings plus the direct-seeded method were used to establish the weed in a field experiment with soybean. In 1996 at 4 wk after emergence (WAE), 8 WAE, and senescence, weeds planted in peat tablets and transplanted at the cotyledon stage were most similar to the direct-seeded method. Peat pots and plastic inserts displayed an intermediate number of differences, whereas direct-seeded–transplanted weeds exhibited the most differences of any propagation method. Transplanting at the two-leaf stage showed more differences, with the four-leaf stage showing even more. In 1997 at 4 WAE, few propagation methods or transplant timings were different from the direct-seeded method. Results from harvests at 8 WAE and at senescence were comparable to those in the previous year. Differences between years at 4 WAE were attributed to greater heat stress and less moisture early in 1996. When common cocklebur was grown in soybean, no differences were detected at 4 WAE between peat tablets transplanted at the cotyledon stage vs. direct-seeded weeds and only one difference when transplanted at the two- and four-leaf stages. At 8 WAE, the early transplant was again the most comparable treatment to direct-seeded weeds, with many differences at the later transplant timings. At senescence, weed differences were no longer apparent. Patterns established for peat tablets with the weed growing alone largely held true when it was grown with soybean.