Annual bluegrass (Poa annua L.) growing in bermudagrass completes its life cycle in May and dies leaving open spaces in the turfgrass. This occurs at a time when summer annual weeds are germinating and these weeds fill the space formerly occupied by the annual bluegrass. As the summer annual weeds die in the fall, annual bluegrass germinates and fills the space formerly occupied by the summer annual weeds. To control annual bluegrass, it is important to control the summer annual grasses and manage the bermudagrass [Cynodon dactylon (L.) Pers.] to maintain a competitive groundcover especially during the peak germination period for the weeds. Herbicide programs over a three-year period were designed to control annual grasses with treatments in April for large crabgrass [Digitaria sanguinalis (L.) Scop.], in May or June for goosegrass [Eleusine indica (L.) Gaertn.] and in late August for annual bluegrass. Oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-ozadiazolin-5-one] applied in August gave complete control of annual bluegrass. Although oxadiazon has a long residual life in the soil, annual bluegrass was poorly controlled with treatments made in June. Fall (August or September) applications of benefin [N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine], prosulfalin N-[[4-(dipropylamino)-3,5-dinitrophenyl] sulfonyl]-S,S-dimethylsulfilimine and butralin [4-(1,1-dimethylethyl-N-(1-methylpropyl)-2,6-dinitrobenzenamine] provided adequate control of annual bluegrass with only a few exceptions during the three-year period. Bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] gave variable control of annual bluegrass; however, this was improved in programs with oxadiazon which provide goosegrass control during summer. In these studies, DCPA [dimethyl tetrachloroterephthalate], even with three applications a year, gave very little control of annual bluegrass. When oxadiazon was used in rotation with DCPA, adequate control was obtained.

Extension workers are sensing pressure to use soils information and chemical characteristics data to guide farmers in selecting pesticides least prone to leach into groundwater. Our objective was to estimate differences in herbicide migration to groundwater under conditions typical for the Southeast Coastal Plain, and to consider how a farmer might be advised to use such knowledge in selecting herbicides. We used a simple computer code for microcomputers to predict persistence and migration of 17 herbicides through a hypothetical, coarse-textured soil typical of the Southeast Coastal Plain. Appropriate herbicides were selected for several common crop-weed problems, such as sicklepod in soybean and Palmer amaranth in corn. Groundwater was assumed to be 3.15 m below the soil surface. Herbicides selected covered a broad range of half-lives and organic carbon partition coefficients. Only after the first-order degradation rate constant was reduced by a factor of five did predicted soil water concentrations of several herbicides at the groundwater interface reach normal detection limits. Still, predicted concentrations were below the level established for health effects advisory purposes. Due to the large number of uncertainties and the inability to estimate practical benefits, we conclude that data relating to soil and herbicide characteristics cannot be used at this time to override cost effectiveness, efficacy, and other factors normally considered by farmers and Extension professionals in herbicides for weed control.

The objective of this investigation was to determine if preemergence herbicides, applied at the standard rates and times for smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl. ♯ DIGIS] control, would provide season-long control of goosegrass [Eleusine indica (L.) Gaertn. ♯ ELEIN] in the transition zone. The transition zone is a unique area of turfgrass culture between cool and warm regions where quality of turfgrasses frequently declines due to environmental stresses. Single and sequential applications of bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] and DCPA (dimethyltetrachloroterephthalate) did not effectively control goosegrass in any of the three test years. Benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) usually required sequential dosages to provide good (90%) to excellent (95%) goosegrass control. Nearly all rates of oxadiazon [2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] used provided good to excellent goosegrass control. Napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] plus bensulide provided excellent goosegrass control in 1981, but not in 1982. Pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] also provided effective goosegrass control.

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.

Large crabgrass [Digitaria sanguinalis (L.) Scop. ♯ DIGSA] control was higher when either DCPA (dimethyl tetrachloroterephthalate) or napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] was applied to bermudagrass [Cynodon dactylon (L.) Pers. ‘Common’] growing in soil with a pH of 5 than in soil with a pH of 6.4 in 2 of 3 yr. Soil pH did not influence the response of large crabgrass to oxadiazon [2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] or benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine). Herbicides alone did not produce high-quality turf unless fertilizer was applied annually at 300 kg N/ha or more. Bermudagrass quality was higher after three yearly applications of 300 kg N/ha or more of fertilizer when soil pH was 5 than when soil pH was 5.6 or 6.4.

Field studies evaluated the effects of crop, crop rotation, planting date, row spacing, no-till planting, and herbicides on wild-proso millet control. Benefin and EPTC reduced wild-proso millet biomass in new seedings of alfalfa, and the combination of herbicides and forage harvest prevented wild-proso millet seed production in that crop. Wild-proso millet seedling populations were reduced and corn yields increased when corn followed 1 to 4 yr of alfalfa. Apparent effectiveness of herbicides in corn increased after cropping with alfalfa. Germination of buried wild-proso millet seed decreased approximately 90% after 54 months which is equivalent to 4-yr prior cropping to alfalfa. Wild-proso millet control and field and sweet corn yields increased when the crops were planted late season (May 17) rather than early season (April 27). Planting sweet corn in rows spaced 76 cm rather than 108 cm apart also increased sweet corn yields. EPTC plus dichlormid (EPTC+) plus cyanazine always controlled wild-proso millet equal to or better than EPTC+ alone. When field corn was planted no-till into killed alfalfa sod, combinations of pendimethalin plus simazine and pendimethalin plus cyanazine provided the best wild-proso millet control and corn yields. But the following year when corn was no-till planted into corn stubble of the identical plots, wild-proso millet control from the same treatments tended to be lower and corn yields were reduced.

Field studies were conducted in 1978 and 1979 on broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] management in peanuts [Arachis hypogaea (L.) ‘Florigiant′]. In both years, preplant incorporated applications of benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] provided better than 75% initial control of broadleaf signalgrass. Preemergence applications of alachlor and metolachlor provided 90% or better initial control. Vernolate (S-propyl dipropylthiocarbamate) and diphenamid (N,N-dimethyl-2,2-diphenylacetamide) provided less than 45% initial control. An at-cracking application of dinoseb (2-sec-butyl-4,6-dinitrophenol) plus naptalam (N-1-naphthylphthalamic acid) plus either alachlor or metolachlor increased control over that provided by at-planting herbicides alone and maximum yields were obtained. No at-planting herbicide alone provided better than 60% control at harvest and consequently yields were lower. In three of four experiments, sequential applications of at-planting and at-cracking herbicides provided better than 75% control at harvest. In the fourth experiment, only benefin and metolachlor followed by at-cracking applications provided better than 70% control at harvest.

Preemergence applications of herbicides were evaluated for their effect on establishment of zoysiagrass (Zoysia japonica Steud.) with competition from either smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl. # DIGIS] or goosegrass [Eleusine indica (L.) Gaertn. # ELEIN]. When ‘Meyer’ and ‘Belair’ zoysiagrass plugs were grown in sand and treated in the greenhouse, none of the herbicides reduced root weight or length. When plugs were grown in a Sassafrass sandy loam, bensulide {O,O-bis(1-methylethyl)-S-[2-[(phenylsulfonyl)amino] ethyl] phosphorodithioate} and simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine) reduced root weight, and simazine reduced root length of Belair, but not Meyer. In smooth crabgrass-infested field plots, more stolons were produced from Meyer plugs treated with simazine, oxadiazon {3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one}, and siduron [N-(2-methylcyclohexyl)-N′-phenylurea] than plugs treated with bensulide, metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one], or the untreated control. At the end of two growing seasons, metribuzin-treated plots had significantly less zoysiagrass than other plots. Oxadiazon, DCPA (dimethyl tetrachloroterephthalate), and siduron enhanced the field establishment rate where Meyer zoysiagrass was competing with high populations of smooth crabgrass.

Field, greenhouse, and laboratory studies were conducted to evaluate the performance of starch xanthide (SX), sludge polymer (SP), and coventional formulations (CF) of benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine], oxadiazon {3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H-one}, and prosulfalin {N-[[4-dipropylamino)-3,5-dinitrophenyl] sulfonyl]-5,5-dimethylsulfilimine} for the control of large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] in Kentucky bluegrass (Poa pratensis L.) turf. Turf injury was greatest with SP oxadiazon and prosulfalin formulations, while SX formulations of oxadiazon and prosulfalin caused decreased and /or delayed injury and provided control comparable to conventional formulations. Coarse SX granules containing prosulfalin caused less turf injury than fine granules, while the opposite effect sometimes occurred with SX oxadiazon. Differences in control were observed in the greenhouse when SX benefin formulations which varied in cross-linking agent and/or degree of substitution were compared to the conventional formulation on sandy and silt loam soils. Benefin SX formulations also demonstrated controlled-release properties, which improved large crabgrass control when compared to the conventional formulation in the greenhouse. This effect was short lived on silt loam but persisted on sand. SX granules cross-linked with Fe3+ extended benefin activity longer than H2O2 cross-linked materials on sandy soil only. Release of 14C-labeled benefin from SX matrices was altered by the extent of water imbibition, solvent characteristics, and granule size.

Wild poinsettia control in peanut was evaluated following various preplant-incorporated and postemergence herbicide applications. The addition of vernolate or alachlor to a preplant-incorporated treatment of benefin improved wild poinsettia control obtained with treatments of lactofen or paraquat plus alachlor applied at the time of peanut emergence. Lactofen applied postemergence following lactofen plus alachlor applied at the time of peanut emergence provided ≥92% wild poinsettia control and peanut yields equivalent to the handweeded control. Treatments of paraquat plus alachlor applied at the time of peanut emergence followed by acifluorfen (applied once or twice) or paraquat followed by acifluorfen provided good (74 to 100%) wild poinsettia control for up to 12 weeks after planting and peanut yields not different from the handweeded plots. Treatments that did not provide at least 92% wild poinsettia control when evaluated 5 weeks after planting resulted in significant peanut yield reduction compared to the handweeded control.

Preemergence (PRE) herbicides may affect the ability to reestablish warm-season turfgrasses in winter-injured areas. Experiments were conducted in 1996 and 1997 to evaluate the effects of fall or spring applications of six PRE herbicides on the vegetative establishment of Tifway bermudagrass, and Meyer and El Toro zoysiagrass. PRE herbicides were applied at the recommended rates during the fall of 1995 and 1996 and at recommended or reduced rates during the spring of 1996 and 1997. Oxadiazon, benefin plus trifluralin, or oryzalin did not inhibit Tifway bermudagrass or zoysiagrass sprig establishment. Fall applications of prodiamine and dithiopyr at full rates suppressed Tifway bermudagrass establishment as much as 25%, but recovery was evident by the end of the growing season. Reduced spring rates of prodiamine diminished its suppressive effects on Tifway establishment. Zoysiagrass establishment was suppressed as much as 20% by full or reduced rates of prodiamine but was less affected by dithiopyr. Pendimethalin had lesser and briefer suppressive effects than prodiamine and dithiopyr had on either species. Results suggested that avoidance of or reduced rates of prodiamine or dithiopyr may be warranted in areas prone to winter injury.

Tropical signalgrass is one of the most serious weed problems in the St. Augustinegrass sod production in Florida, and its presence increases production costs and lowers turfgrass quality. The objectives of our research were to: (1) evaluate herbicides preemergence and postemergence for control of tropical signalgrass and (2) compare control of tropical signalgrass and other problem weeds (torpedograss, blanket crabgrass, and India crabgrass) with postemergence herbicides. In preemergence herbicide field trials, only benefin + oryzalin, imazapic, imazapic + 2,4-D, and oryzalin provided ≥75% tropical signalgrass control 8 wk after application (WAA). By 11 WAA, only benefin + oryzalin and imazapic + 2,4-D provided ≥75% tropical signalgrass control. In greenhouse experiments, eight herbicide treatments were applied postemergence to tropical signalgrass seedlings at the two-, four-, six-, and eight-leaf stages. Asulam and CGA 362622 provided ≥89% tropical signalgrass control at all application timings. Imazaquin controlled tropical signalgrass ≥98% when applied before the eight-leaf stage. However, in field trials with mature tropical signalgrass (>20 cm stolons), none of the 20 herbicide treatments applied postemergence provided acceptable control.

Field trials were conducted in 1995 through 2002 to expand the development of chicory by determining the potential for tank mixtures of benefin, trifluralin, or pronamide applied preplant incorporated (PPI) and triflusulfuron methyl or imazamox postemergence (POST) for selective weed control in chicory. Lack of early-season weed control resulted in an 88% reduction in chicory root yield in 1995 to 1996 and an 85% reduction in 2001 to 2002 and demonstrated the susceptibility of chicory plants to early-season weed competition. In the first experiment, pronamide at 1.1 kg ai/ha PPI plus benefin at 1.3 kg ai/ha or trifluralin at 0.56 kg/ha were selective for chicory and controlled weed populations 90% on average with root yields that were 89% of the hand-weeded treatment. Triflusulfuron methyl POST at 17 g/ha caused early-season chicory injury. In the second experiment, trifluralin PPI at 0.56 kg/ha followed by imazamox POST at 36 g/ha controlled weeds 95% on average with a chicory root yield of 74 t/ha, which was 109% of the yield of the hand-weeded treatment.

Preemergence (PRE) and postemergence (POST) herbicides registered for large crabgrass control were evaluated for control of Japanese stiltgrass, an invasive, nonnative C4 annual grass. Benefin plus oryzalin, dithiopyr, isoxaben plus trifluralin, oryzalin, oxadiazon, pendimethalin, prodiamine, or trifluralin applied PRE controlled Japanese stiltgrass 87% or greater 8 wk after treatment. Benefin plus trifluralin, metolachlor, or napropamide applied PRE were less effective (78, 39, and 59% control, respectively). Single POST applications of clethodim, fenoxaprop-P, fluazifop-P, or sethoxydim controlled Japanese stiltgrass 50 to 88%. These herbicides applied twice provided 82 to 99% control. Single POST applications of glufosinate controlled Japanese stiltgrass 82 to 85%, whereas two applications provided complete control. Single POST applications of glyphosate were just as effective as two applications in controlling Japanese stiltgrass. Dithiopyr, MSMA, and quinclorac applied POST were ineffective on Japanese stiltgrass. All PRE and POST herbicides tested were equally or more effective on Japanese stiltgrass than on large crabgrass, with the exception of metolachlor applied PRE and dithiopyr or quinclorac applied POST.