There were usually no significant differences in weed and crop yields between plots receiving aerial and ground applications of herbicides. Where differences were found, aerial application was the more effective.

Two Louisiana sugarcane cultivars (interspecific hybrids of the genus Saccharum) CP 52–68 and L 60-25 were sprayed with herbicides commonly used for preemergence and postemergence control of johnsongrass (Sorghum halepense (L.) Pers.) and other weeds. The preemergence weed control treatments of 3-tert-butyl-5-chloro-6-methyluracil (terbacil) at 1.8 kg/ha and (2,3,6-trichlorophenyl)acetic acid (fenac) at 5 kg/ha were compared to a mixture of sodium salt of trichloroacetic acid (TCA) at 11 or 19 kg/ha plus 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) at 3.4 kg/ha (control). Herbicides were applied after planting in the fall, reapplied the following spring (after sugarcane emerged), and applied again in the second spring on the stubble crop (after sugarcane emerged). In the stubble crop the sodium salt of 2,2-dichloropropionic acid (dalapon) at 0, 5, or 10 kg/ha was applied as a postemergence spray over the top of sugarcane. In the factorial arrangement each cultivar received all combinations of the preemergence x postemergence treatments.

Terbacil did not injure either cultivar, but fenac injured both enough to reduce the yield of sugar in plant cane by about 10% as compared to the TCA plus silvex control. Stubble crop yields were not affected by fenac or terbacil. CP 52–68 was more tolerant to dalapon treatments than L 60–25. Both cultivars tolerated dalapon at 5 kg/ha relatively well although the yield of L 60–25 was reduced by about 5%. However at 10 kg/ha, dalapon reduced yields of CP 52–68 and L 60–25 by about 10 and 18%, respectively. Combinations of preemergence and postemergence treatments did not interact to reduce yields more than the combined effects of each treatment.

Hydrilla is one of the most serious aquatic weed problems in the United States, and fluridone is the only U.S. Environment Protection Agency (USEPA)–approved herbicide that provides relatively long-term systemic control. Recently, hydrilla biotypes with varying levels of fluridone resistance have been documented in Florida. Several biotypes of hydrilla varying in resistance levels were maintained in 950-L tanks under ambient sunlight and day-length conditions from September 2004 to September 2005 in absence of fluridone. Phenotypic measurements were performed during this 1-yr period to monitor differences in growth and reproductive physiology. All fluridone-resistant biotypes (except R3) were growing at the same rate or greater than the susceptible hydrilla. These data suggested that there are no deleterious effects on growth and reproductive physiology because of development of fluridone resistance. Aggressive spread of fluridone-resistant dioecious hydrilla in aquatic ecosystems can severely affect hydrilla management and, consequently, cause substantial and long-lasting ecological and economic problems throughout the southern United States.

Maximum germination of flodman thistle [Cirsium flodmanii (Rydb.) Arthur ♯3 CIRFL] occurred at alternating temperatures of 10 to 20 and 20 to 30 C. Seeds germinated (20%) in 1.7 M NaCl. Light was important in seed germination; however, its absence could be overcome by adding 8.6 × 10-5 M GA3 (gibberellic acid) to the germination medium. The greatest seedling emergence occurred when seeds were planted on the soil surface and was lower when seeds were buried at any depth in the soil. Osmotic potentials at −0.5 MPa and greater reduced germination, but 3% of the seeds germinated at −1.3 MPa. Flodman thistle seedlings tolerated average plant water potentials of −0.9 and −1.1 MPa, but they died when the water potential was decreased to −1.5 MPa. Flodman thistle seedlings 43 days old and with four true leaves resprouted after topgrowth removal. Regrowth was evident on 75% of the clipped plants 13 days after initial topgrowth removal. Flodman thistle rosettes spread more rapidly and rosette survival was enhanced more in a weed-free nursery than in a weedy pasture.

Nine field trials were carried out during 1968 and 1969 to study selective weed control in sugarbeets (Beta vulgaris L.) by preemergence and postemergence applications. The trials were conducted at various regions of Israel, under a wide range of climatic and edaphic conditions. Among the preemergence treatments, the herbicide 1-methyl-3-(2-benzothiazolyl)-urea (hereinafter referred to as benzthiazuron) gave adequate weed control and selectivity to sugarbeets. However, when heavy infestation with grasses was present, an addition of isopropyl carbanilate (propham) was needed to increase the spectrum of weed control. A preemergence application of 1-butyl-3-(3,4-dichlorophenyl)-1-methylurea (neburon) on each side of the drill-row of sugarbeets together with an over-band application of benzthiazuron or 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) improved weed control. Among postemergence treatments, a mixture of pyrazon and propham gave excellent broad-spectrum weed control. Applying this combination in an emulsion with a non-phytotoxic oil considerably improved weed control.

Analysis for total carbohydrate content was made on oven dried bermudagrass [Cynodon dactylon (L.) Pers.] dallisgrass (Paspalum dilatatum Poir.) and smutgrass [Sporobolus poiretii (R. & S.) Hitchc.] storage tissue collected at 2, 4, 6, or 36 weeks after fall treatment and at 2, 4, or 6 weeks after fall and spring treatment with three herbicides at varying rates. Those species that survived either fall or fall and spring herbicide application exhibited an initial reduction in carbohydrate content, but it returned to a level comparable to that in the untreated plants in most instances within 6 weeks after treatment. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] at 4.48 and 8.96 kg/ha and bromacil (5-bromo-3-sec-butyl-6-methyluracil) at 2.24 and 4.48 kg/ha resulted in carbohydrate reduction in bermudagrass and dallisgrass for no more than 6 weeks except where both fall and spring treatments were used. Smutgrass was controlled with these two herbicides within 2 weeks so that not enough live tissue was available for analysis. There was no carbohydrate reduction in bermudagrass with the 2.24, 4.48, or 8.96 kg/ha rates of MSMA (monosodium methanearsonate) beyond 2 weeks following treatment. The carbohydrate content of smutgrass was reduced up to 6 weeks after treatment with MSMA, and dallisgrass was controlled at all rates so that no carbohydrate analysis could be made.

Field experiments were conducted to study the effect of fall and spring pre-plant incorporated applications of trifluralin (α,α,α-tri-fluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)-one] alone and in combinations on crop tolerance, seed yield, and weed control in fababeans (Vicia faba L. ‘Diana’). Trifluralin applied either in the fall or the spring resulted in acceptable control of green foxtail [Setaria viridis (L.) Beauv.] and wild oat (Avena fatua L.) while metribuzin resulted in excellent control of wild mustard [Brassica kaber (DC.) L.C. Wheeler var. pinnatifida (Stokes) L.C. Wheeler]. In 2 out of 3 yr, a tank-mixture of trifluralin plus metribuzin applied in the fall at 1.4 and 0.4 kg/ha, respectively, resulted in significantly larger seed yield than the same combination applied at 1.1 and 0.3 kg/ha in the spring. Although the fall treatments generally resulted in higher seed yields, there was no consistent difference in weed densities between fall and spring applications. In both field and growth room studies, trifluralin reduced the injury to fababeans from metribuzin. A postemergence application of metribuzin in the spring at 0.3 kg/ha following a fall-application of trifluralin resulted in good wild mustard control but caused considerable crop damage. Dinoseb (2-sec-butyl-4,6-dinitrophenol) and bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2dioxide] controlled wild mustard effectively with no injury to the crop.

Field experiments were conducted over a 4-yr period to determine the influence of selected herbicides on ozone injury in tobacco (Nicotiana tabacum L.). Isopropalin (2,6-dinitro-N,N-dipropylcumidine), pebulate (S-propyl butylethylthiocarbamate), and diphenamid (N,N-dimethyl-2,2-diphenylacetamide) were applied at the recommended rates of 1.7, 4.5, and 4.5 kg/ha, respectively. Treatment of tobacco plants with isopropalin or diphenamid reduced oxidant injury for the first 2 to 4 weeks after transplanting, but not later in the season. Pebulate had no consistent affect on the sensitivity of tobacco to ozone.

The competitive ability of annual round-leaved mallow was determined in spring wheat and lentil at Indian Head and Regina, Saskatchewan, in 1985 and 1986 using paired quadrats. Significant biomass and seed yield loss occurred in three of four tests in lentil and two of three tests in spring wheat. Differences in numbers of wheat tillers produced between weedy and weed-free plots were found in three of four tests. A two-variable model comprised of early season crop density loss and round-leaved mallow biomass best accounted for the majority of variation in crop yield loss for both lentil and wheat, and tiller density loss in wheat. In 1985 at Indian Head, where no yield loss occurred for either wheat or lentil, round-leaved mallow had been seeded immediately before the crop. Greater yield losses occurred at Regina, in the presence of an older, well-established infestation. In the years and locations with the greatest crop yield losses, round-leaved mallow emerged before the crop causing poor crop emergence. At Regina in 1986, crop yield losses were more than 60% in wheat and 90 to 100% in lentil because of large differences in crop density between weed-free and weedy subplots. Round-leaved mallow exhibited great variability in growth, producing more biomass per plant, more capsules per plant, and more capsules per gram of biomass in the less competitive crop, lentil, than in wheat. Density and biomass of round-leaved mallow were not correlated; with a density of 200 plants m−2, round-leaved mallow biomass in wheat ranged from 100 to 500 g m−2; while in lentil, from 200 to as high as 1000 g m−2, approximately double the range found in wheat. The type of round-leaved mallow infestation (newly seeded or well-established) and environmental conditions (mainly early season precipitation) account for differences between sites and between years.

The effect of alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] and gibberellic acid (GA3) on increase in length of corn (Zea mays L.) epicotyl segments and the interactions between alachlor (0, 5 × 10-6, 5 × 10-4, 4.4 × 10-4, and 5 × 10 M) and GA3 (0, 1 × 10-6, 2.8 × 10-4, and 1 × 10-4 M) were investigated. Alachlor significantly inhibited growth of these segments while GA3 usually increased growth. GA3 in combination with alachlor caused a significant increase in growth compared to alachlor alone resulting in growth comparable to that occurring in untreated tissues. The magnitude of GA3 induced growth in the presence of alachlor depended upon the concentrations of the herbicide and GA3 employed. Alachlor was, however, able to inhibit the GA3 induced growth. The maximum degree of growth inhibition resulted from exposure of the segments to alachlor with or without GA3 from the start of incubation. This inhibition decreased as the exposure to alachlor was delayed. Alachlor started inhibiting growth in the presence of GA3 after the first 9 hr of incubation and after the first 21 hr of incubation in the absence of GA3.

Alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] at 3.4 kg/ha, EPTC (S-ethyl dipropylthiocarbamate) + R-25788 (N,N-diallyl-2,2-dichloroacetamide) at 4.5 + 0.4 and 9.0 + 0.8 kg/ha, vernolate (S-propyl dipropylthiocarbamate) + R-25788 at 4.5 + 0.4 and 9.0 + 0.8 kg/ha, metolachlor [2-chloro N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] at 1.7 and 3.4 kg/ha, and metolachlor + procyazine {2-[[4-chloro-6-(cyclopropylamino)1,3,5-triazine-2-yl] amino]-2-methylpropanenitrile} at 1.3 + 1.3 kg/ha were preplant incorporated. These herbicides controlled 95% or more of the barnyardgrass [Echinochloa crus-galli (L.) Beauv.], common lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), Powell amaranth (A. powellii S. Wats.), and yellow foxtail [Setaria lutescens (Weigel) Hubb.] without injuring sweetcorn (Zea mays L. ‘Golden Jubilee’) or reducing corn yields or quality. Similar results were obtained with preplant incorporated applications of butylate (S-ethyldiisobutylthiocarbamate) + R-25788 at 4.5 + 0.2 kg/ha followed by a postemergence application of the amine salt of 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 0.6 kg/ha. Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] at 0.3 and 0.6 kg/ha and metribuzin + alachlor at 0.6 + 2.2 kg/ha applied preplant and incorporated reduced corn stands, primary ear production, and corn yields significantly. None of the herbicides significantly affected total sugars, reducing sugars, soluble solids, moisture content, or succulence of the corn.

Spring parsley [Cymopterus watsonii (Coult. & Rose) Jones] was examined for phototoxicity by chick (Gallus domesticus, Arbor Acre 50 x Vantress hybrid) bioassay, after treatment with 2,4,-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 4-amino-3,5,6-trichloropicolinic acid (picloram), and an approximate 4 to 1 mixture of 2,4-D and picloram. Spring parsley leaves treated with picloram and picloram-2,4-D were much less phototoxic to chicks than controls 4 weeks after treatment. When treatment was followed by warm weather, leaves treated with 2,4-D and 2,4,5-T were not phototoxic 4 weeks after treatment at the highest single dose that could be administered.

Mesotrione is an effective herbicide for volunteer potato control but is not selective in several crops, including onion and carrot. Studies were conducted in 2006 to evaluate the effectiveness of wiper-applied mesotrione for control of volunteer potato in a potato crop. Surprisingly, nontreated potatoes growing adjacent to mesotrione-treated plants exhibited bleaching symptoms resembling mesotrione injury. Additional field trials confirmed injury to nontreated plants growing within 26 cm of potatoes treated with mesotrione applied with a wiper at 0.25, 0.5, and 1% (v/v) solutions. Greenhouse bioassays confirmed that mesotrione applied to potato leaves moved down through the plant and was exuded into perlite potting medium in sufficient quantities to injure potato plants that were exposed to the leachate from the perlite pots. In tracer studies, 52% of 14C-labeled mesotrione applied to potato leaves was absorbed into the potato plant by 15 d and 15% of the absorbed 14C-mesotrione was exuded into the soil and soil leachate. Mesotrione applied to potato by the wick application method has potential to injure neighboring susceptible plants from root uptake of exuded mesotrione.

This research studies whether photoprotection mechanisms are able to counterbalance the short-term effect of two herbicides, acifluorfen methyl (AFM) and paraquat (PQ), that generate photo-oxidative stress in different subcellular locations. Duckweed plants grown under three light intensities (high-, medium-, and low light), and consequently expressing three levels of photoprotection, were exposed to both herbicides under the same light regime. Oxidative damage induced by AFM originated mainly from the cytosolic accumulation of protoporphyrin IX, leading to a process of plasma membrane disruption, a progressive and slow degradation of ascorbate and photosynthetic pigments, and glutathione accumulation. As most photoprotective mechanisms (antioxidants and xanthophylls-cycle-related energy dissipation) operate mainly within the chloroplast, these systems were unable to protect plants from AFM damage irrespective of the level of light acclimation. Paraquat effects developed more rapidly and to a greater extent than AFM in treated plants. Irrespective of the light intensity, the same sequence of degradation was observed: ascorbate followed by glutathione, α-tocopherol, pigments, and membrane disruption. In PQ-treated plants the generation of oxidative stress occurred mainly in the chloroplast, and cellular damage developed more slowly in highly photoprotected plants (high light); in fact, electrolyte leakage can be used as a marker for PQ tolerance. The effects of both herbicides indicate that the xanthophyll cycle is an early protective mechanism and confirms the central role of ascorbate in early photoprotection response. High levels of lipophilic and hydrophilic antioxidant contents did not lead to attenuated phytotoxicity of acifluorfen methyl and thus are not the basis to explain differential susceptibilities among duckweed plants.

Field studies were conducted in 1981 to 1983 to evaluate selected herbicides for control of a natural infestation of woolly croton (Croton capitatus Michx. ♯ CVNCP) in soybean [Glycine max (L.) Merr.]. Ineffective woolly croton control was obtained with all preemergence herbicides evaluated. Early postemergence treatments of acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} and lactofen {1-(carboethoxy)ethyl) 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate} provided excellent woolly croton control. Postdirected applications of oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] applied at the V4 stage of soybean growth and tank mixes of cyanazine {2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl] amino]-2-methylpropanenitrile}, linuron [N′-(3,4-dichlorophenyl)-N-methoxy-N-methylurea], or metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] plus 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] applied at the V4 and repeated at the V6 stage of soybean growth also provided effective control.

Junglerice [Echinochloa colona (L.) Link] is increasing its prevalence in eastern Australia by adapting to Australia’s changing climatic conditions and conservation agricultural systems and by evolving resistance to glyphosate. Information is limited on the growth and seed production dynamics of E. colona when it interferes with mung bean [Vigna radiata (L). R. Wilczek], a major potential export crop for eastern Australia. This field study examined the interference of E. colona in mung bean for two summer seasons (2020 and 2021) at Gatton, QLD. Different infestation levels (0, 2, 4, 8, 16, and 32 plants m−2) of E. colona were assessed for their potential to cause yield reductions in mung bean. Seed yield of mung bean was highest in the weed-free plots (2,767 kg ha−1) and declined by 20%, 27%, 34%, and 43% at weed infestation levels of 4, 8, 16, and 32 plants m−2, respectively. Echinochloa colona biomass in mung bean varied from 11 to 137 g m−2 as weed density increased from 2 to 32 plants m−2. Based on a three-parameter hyperbolic rectangular decay model, crop yield loss was 52% and 57%, respectively, when weed density and weed biomass approached maximum. Echinochloa colona at the highest density (32 plants m−2) produced a maximum of 15,140 seeds m−2, and this seed production was reduced by 50% at a weed density of 10 plants m−2. Echinochloa colona plants retained 63% to 68% seeds at mung bean maturity, indicating a great opportunity for harvest weed seed control. This study suggests that a high infestation of E. colona in mung bean fields could cause a substantial yield loss and increase the weed seedbank.

Alfalfa (Medicago sativa L.) hectares in Michigan are declining partly due to reliance on corn (Zea mays L.) silage as a continuous feed source. By interseeding corn and alfalfa, farmers can replace the low alfalfa yield in the establishment year with corn silage while simultaneously establishing alfalfa. A randomized split-block field study was conducted in East Lansing, MI, over 3 yr (2019 to 2021) to determine the critical period of weed control (CPWC) in the interseeded corn and alfalfa system using two corn hybrids with differing leaf architecture (pendulum vs. upright). Whole plots were assigned to corn hybrids interseeded with alfalfa, and subplots were assigned to a surrogate weed, Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz], for the duration of competition treatments. Weed-free and weedy plots were included as controls. At the end of the interseeding year, corn was harvested, while alfalfa was harvested the following year. The CPWC is made up of two components: the critical timing of weed removal (CTWR) and the critical weed-free period (CWFP). Corn hybrid had no impact on the CTWR or CWFP for interseeded corn or alfalfa. Averaged across hybrids, the CTWR was 303 growing degree days (GDD), and CWFP was estimated to be greater than the study duration. The CTWR in the first cutting of alfalfa was estimated to be 369 GDD. The CWFP was estimated to be 394 GDD for a 5% acceptable yield loss for the first alfalfa cutting. Identification of the CPWC in the interseeded system will increase adoption and interest in other interseeded systems that can mitigate potential negative environmental and economic impacts of monoculture agriculture.

Alkali barnyardgrass [Echinochloa crus-galli var. zelayensis (Kunth) Hitchc] and junglerice [Echinochloa colona (L.) Link] are problematic annual weeds in direct-seeded rice (Oryza sativa L.) fields in China. The emergence ecology of the two weed species may differ in response to environmental factors. Laboratory and screenhouse experiments were conducted to evaluate the effects of light, burial depth, mulching with wheat (Triticum aestivum L.) residue, and time and depth of flooding on the emergence of the two weed species collected from Nanjing, China. Light strongly increased seed germination. Under dark conditions, E. crus-galli seed germination (85%) was higher than that of E. colona (70%). The seeds of both species exhibited the greatest germination (90% for E. crus-galli and 80% for E. colona) when sown on the soil surface, and emergence decreased with increasing soil burial depth. Burial depths of 2.2 and 1.4 cm reduced seedling emergence by 50% for E. crus-galli and E. colona, respectively. No emergence was found at a depth of 6 cm. The seedling emergence for E. colona was lower than for E. crus-galli at the same soil burial depth. Mulching with wheat residue considerably reduced the seedling emergence and aboveground biomass of both species. The inhibitory effect of mulching with wheat residue on E. colona was more notable than on E. crus-galli. Early and deep flooding significantly suppressed the emergence, height, and biomass of E. crus-galli and E. colona, especially E. colona. The results gained from this study could provide fundamental ecological knowledge for managing Echinochloa species in direct-seeded rice systems.

The genus Echinochloa constitutes some of the most prominent weed species found in rice (Oryza sativa L.) production worldwide. The taxonomy of Echinochloa is complex due to its morphological variations. The morphophysiological diversity and taxonomic characteristics of Echinochloa ecotypes infesting rice fields in Texas are unknown. A total of 54 Echinochloa ecotypes collected during late-season field surveys in 2015 and 2016 were characterized in a common garden in 2017. Plants were characterized for 14 morphophysiological traits, including stem angle; stem color; plant height; leaf color; leaf texture; flag leaf length, width, and angle; days to flowering; panicle length; plant biomass; seed shattering; seed yield; and seed dormancy. Principal component analysis indicated that 4 (plant height, flag leaf length, seed shattering, and seed germination) of the 14 phenological traits characterized here had significantly contributed to the overall morphological diversity of Echinochloa spp. Results showed wide interpopulation diversity for the measured traits among the E. colona ecotypes, as well as diverse intrapopulation variability in all three Echinochloa species studied, including barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], junglerice [Echinochloa colona (L.) Link], and rough barnyardgrass [Echinochloa muricata (P. Beauv.) Fernald]. Taxonomical classification revealed that the collection consisted of three Echinochloa species, with E. colona being the most dominant (96%), followed by E. crus-galli (2%), and E. muricata (2%). Correlation analysis of morphophysiological traits and resistance status to commonly used preemergence (clomazone, quinclorac) and postemergence herbicides (propanil, quinclorac, imazethapyr, and fenoxaprop-ethyl) failed to show any significant association. Findings from this study provided novel insights into the morphophysiological characteristics of Echinochloa ecotypes in rice production in Texas. The morphological diversity currently present in Echinochloa ecotypes could contribute to their adaptation to selection pressure imposed by different management tools, emphasizing the need for a diversified management approach to effectively control this weed species.

In laboratory and field studies, quackgrass (Agropyron repens (L.) Beauv. # AGRRE) was subjected to postemergence applications of the butyl ester of fluazifop-P {(R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, methyl ester of haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, or ethyl ester of quizalofop {2-[4-[[6-(chloro-2-quinoxalinyl)oxy] phenoxy] propanoic acid}. Haloxyfop, fluazifop-P, and quizalofop each required a minimum of 1 week to reduce quackgrass transpiration or water uptake in the laboratory. At rates lower than 0.56 kg ae/ha, fluazifop-P reduced quackgrass transpiration and water usage less quickly and to a lesser extent than equivalent rates of haloxyfop and quizalofop. The time required for significant transpiration and water uptake reduction by herbicide-treated quackgrass was several days longer in the field than in the laboratory, but the reaction patterns among the herbicides were similar. Little if any benefit was obtained from sequential applications of the herbicides compared with single applications of the same total dosage. All three herbicides significantly reduced quackgrass dry weight.