Dimethyl Tetrachloroterephthalate Research Articles

Evaluation of Herbicide Programs in Florida Cabbage Production

In Florida, cabbage (Brassica oleracea L.) is typically grown without a plastic mulch and as a result, weeds are a significant problem in most fields. Experiments were conducted from Nov. 2015 to Apr. 2016 in Balm, Citra, and Parrish, FL, to evaluate weed control and ‘Bravo’ cabbage tolerance to multiple herbicide programs applied pretransplanting (PRE-T), posttransplanting (POST-T), PRE-T followed by (fb) a sequential application at 3 weeks after transplanting (WATP), and POST-T fb sequential application at 3 WATP. PRE-T herbicide treatments of 277 g a.i./ha clomazone, 280 g a.i./ha oxyfluorfen, and 798 g a.i./ha pendimethalin and POST-T herbicide treatments of 6715 g a.i./ha dimethyl tetrachloroterephthalate (DCPA) were ineffective, and weed control never exceeded 70% in Balm and provided <50% weed control in Citra and Parrish at 6 and 8 WATP, respectively. POST-T applications of napropamide + S-metolachlor at 2242 + 1770 g a.i./ha, DCPA + S-metolachlor at 6715 + 1170 g a.i./ha, and S-metolachlor POST-T fb clopyralid at 1170 g a.i./ha fb 210 g ae/ha were the most effective herbicide treatments and consistently provided >70% weed control. In addition, results showed that all of the herbicide treatments evaluated except the PRE application of clomazone at 277 g a.i./ha are safe for cabbage with no adverse effect on yield.

Corn-based Extracts to Manage Weeds and Provide Nitrogen in Matted-row Strawberry Culture

The number of herbicides available for use in strawberry (Fragaria×ananassa Duch.) production is limited. Corn gluten hydrolysate (CGH) is a water-soluble extract of corn gluten meal (CGM), a by-product of corn wet-milling. Both CGH and CGM have been shown to inhibit root development of seedlings and can provide nitrogen (N). Four weed control and/or N- containing products were studied: CGH, CGM, urea (46N-0P-0K), and urea applied with DCPA at 8.4 kg·ha-1 a.i. Treatments were applied at N rates of 0, 9.8, 19.5, and 29.3 g·m-2. The 0 g·m-2 of N treatment served as the control. During the 1995 establishment season, all treatments were applied in June, July, and August. Treatments were applied in July and August during the 1996, 1997, and 1998 growing seasons. Dicot and monocot weed number and weed shoot dry weights were determined ≈30 days after both July and August treatments. Strawberry yield data were collected in June. Leaf N data were collected during the first week of July, before renovation. When CGH was applied in July, dicot weed number in August decreased in one of four years, but CGH never affected the number of monocot weeds. CGM application in July, reduced the number of dicot weeds found in plots in Aug. 1995 and 1998. Urea had no effect on dicot weed number from 1995 to 1997. However, in 1998, dicot weed number was reduced by as much as 79% as the rate of urea increased. In all study years, dicot weed number was reduced between 86% and 97%, for the high rate of DCPA + urea, compared with control plots. With few exceptions, rate of N had no effect on leaf N or yield. CGH exhibited limited potential as a natural weed control product; it reduced dicot weed number in one year, but did not affect the number of monocot weeds in any year. Strawberry yield in plots receiving CGH showed a linear increase in one year (1998), but did not show an increase in the other 2 years. Chemical name used: dimethyl tetrachloroterephthalate (DCPA)

The relationship between land use and organochlorine compounds in streambed sediment and fish in the Central Columbia Plateau, Washington and Idaho, USA

AbstractWe analyzeds streambed sediment and fish in the Central Columbia Plateau in eastern Washington and Idaho for or ganochlorine pesticides and polychlorinated biphenyls (ΣPCB). Our objective was to assess the effects of land use on the occurrence and distribution of these compounds; land uses in the study area included forest, dryland and irrigated farming, and urban. We detected 16 organochlorine compounds in streambed sediment and fish tissue; fish usually had more compounds and a greater frequency of detection. The most frequently detected compound was ΣDDT (sum of six isomers), which was found in 52% of bed sediment samples and 94% of whole fish composite samples. The other commonly detected compounds were dimethyl tetrachloroterephthalate (DCPA), dieldrin, hexachlorobenzene, and Σchlordane (sum of cis‐ and trans‐chlordane, cis‐ and trans‐nonachlor oxychlordane, heptachlor, and heptachlor epoxide). Forest was the only land use with no detections of organochlorine compounds in either fish or bed sediment. Hexachlorobenzene was the only organochlorine pesticide detected at concentrations that differed significantly among land uses: concentrations were higher in the dryland farming areas than in the irrigated farming or urban areas. In agricultural areas irrigated by surface water, ΣDDT concentrations in both streambed sediment and fish tissue were related to the percentage of land irrigated by water delivered via furrows (gravity irrigation), although ΣDDT was not detectable in bed sediments until gravity irrigation exceeded 30%. Because of the relation between gravity irrigation and soil erosion, our study supports the importance of controlling soil erosion in order to reduce the overall loading of organochlorine compounds to surface waters.

Determination of the metabolites of the herbicide dimethyl tetrachloroterephthalate in drinking water by high-performance liquid chromatography with gas chromatography/mass spectrometry confirmation.

Two metabolites of the herbicide dimethyl tetrachloroterephthalate, (DCPA), monomethyl tetrachloroterephthalate (MM) and tetrachloroterephthalic acid (TCPA), are assayed via high-performance liquid chromatography with ion paring. Samples are analyzed via direct injection, without preparation, and analyte detection is accomplished with an ultraviolet photodiode array detector. The metabolites are extracted from positive samples with a petroleum ether/diethyl ether mixture, derivatized with N,O-bis(trimethylsilyl) trifluoracetamide, and confirmed by way of gas chromatography/mass spectrometry. The HPLC analysis of 200 spiked drinking water samples yielded a recovery range of 92-106% with a mean recovery of 101% for TCPA and a recovery range of 92-101% with a mean recovery of 96% for MM. The minimum detection limits for TCPA and MM were 2.4 and 2.7 micrograms/L, respectively. In addition, the GC/MS analysis of spiked reagent water yielded mean recoveries of 91% for MM and 86% for TCPA. Twenty drinking water samples were split and analyzed by the HPLC and GC/MS methods and by USEPA Method 515.1. Comparable results were obtained. The HPLC method, which is amenable to automation, typically allows for the analysis of up to 40 samples overnight.

Crabgrass Control and Dollar Spot Suppression in Creeping Bentgrass with DSMA

Research was conducted to evaluate crabgrass [Digitaria ischaemum (Schreb.) Muhl.] control, incidental dollar spot (incited by Lanzia and Moellerodiscus spp.) suppression, and turfgrass quality following sequential, low-level postemergence applications of DSMA to creeping bentgrass (Agrostis stolonifera var. palustris Farwell). DSMA was applied at 22 mg·m-2 at 7-day intervals for 15 consecutive weeks (DSMA-W) from May through Aug. 1986 and 1987 and for 10 consecutive weeks from June through Aug. 1988. DSMA also was applied in three split applications of 110 mg·m-2 every 10 days (DSMA-S) in June and July of each year. DCPA was applied in a single, preemergence application in May as a comparative standard for crabgrass control. Percent crabgrass in either DSMA-treated plot was 20% by 11 Sept., an infestation that was unacceptable for high-quality turf. Percent crabgrass infestation was 6% at all rating dates in 1987 or 1988 for DSMA-W and 11% at all dates in 1987 or 1988 for DSMA-S. DCPA significantly reduced percent crabgrass as compared to the nontreated control at all rating dates, but the percent crabgrass ratings tended to be higher than those for either DSMA treatment by the final rating dates of each year. The DSMA treatments significantly reduced dollar spot incidence in each year. Turfgrass discoloration was observed following the DSMA-S treatment in July 1987 as compared to the control, but the turf quality recovered by August. Turfgrass quality was higher for DSMA treatments than for either DCPA or the nontreated control due to season-long crabgrass control and disease suppression. Chemical names used: disodium methanearsonate (DSMA), dimethyl tetrachloroterephthalate (DCPA).

Occurrence and distribution of organochlorine compounds in sediment and livers of striped bass ( Morone saxatilis) from the San Francisco Bay-Delta Estuary

A preliminary assessment was made in 1992 of chlorinated organic compounds in sediments and in livers of striped bass from the San Franciso Bay-Delta Estuary. Samples of sediment and striped bass livers contained DDT (ethane, 1,1,1-trichloro-2,2-bis (p-chlorophenyl)-) and its degradation products, DDD (ethane, 1,1-dichloro-2,2-bis(p-chlorophenyl)-) and DDE (ethylene, 1,1-dichloro-2,2-bis (p-chlorophenyl)-); PCBs (polychlorinated biphenyls); alpha and gamma chlordane, and cis and trans nonachlor. In addition, the livers of striped bass contained small concentrations of DCPA (dimethyl tetrachloroterephthalate), a pre-emergent herbicide. Agricultural run-off from the Sacramento and San Joaquin Rivers, as well as atmospheric deposition, are probably responsible for a low chronic background of DDT in sediments throughout San Francisco Bay. Larger concentrations of DDT in sediment near Richmond in the Central Bay, and Coyote Creek in the South Bay may be derived from point sources. Ratios of pentachloro isomers of PCBs to hexachloro isomers in the South Bay sediments were different from those in the Central and North Bay, suggesting either differences in microbial activity in the sediments or different source inputs of PCBs. Concentrations of alpha chlordane in livers of striped bass were greater than those of gamma chlordane, which suggests a greater environmental stability and persistence of alpha chlordane. Trans nonachlor, a minor component of technical chlordane, was present in greater concentrations than alpha and gamma chlordane and cis nonachlor. Trans nonachlor is more resistant to metabolism than alpha and gamma chlordane and cis nonachlor, and serves as an environmentally stable marker compound of chlordane contamination in the estuary. Chlorinated organic compounds have bioaccumulated in the livers of striped bass. These compounds may contribute to the decline of the striped bass in San Francisco Bay-Delta Estuary.

Immunofluorescence and electron microscopic investigations of DCPA-treated oat roots

Immunofluorescence and electron microscopy were used to investigate the effects of DCPA (dimethyl tetrachloroterephthalate) on oat roots. Phragmoplast microtubule arrays were the most consistently affected. Multiple phragmoplasts, undulated phragmoplasts, branched phragmoplasts, and phragmoplasts arising at places other than that predicted by the preprophase band were all observed. Cell wall formations resulting from these abnormal phragmoplast configurations are also abnormal and consist of reticulate cell plates, walls formed at abnormal angles, and wall material in net-like arrays containing pockets of cytoplasm. Cortical and preprophase band microtubule arrays were unaffected, and were similar in both treated and control cells. Minispindle and multipolar spindles were observed in some meristematic cells, although many spindle formations were normal or nearly so. Some multiple and highly lobed nuclei were also found as a consequence of these abnormal divisions. Cell plates were abnormal even when there were no nuclear abnormalities that would cause physical disruption of the division plane and even though preprophase bands (which are predictive of the subsequent plane of division) were normal. These data indicate that DCPA has a direct effect on phragmoplast microtubule organizing centers.

Volatilization, Off‐Site Deposition, and Dissipation of DCPA in the Field

AbstractResidues of dimethyl, 2,3,5,6‐tetrachloroterephthalate (DCPA) have been found repeatedly in recent years on a variety of produce grown in California to which this herbicide had not been applied. In response to this problem, drift, volatilization, and dissipation of DCPA were investigated in a circular plot seeded with bunch onions [Allium cepa (L.) var. White Lisbon], and off‐site deposition was measured in a surrounding area seeded with parsley [Petroselinum crispum (Mill.) Mansf. var. Green Modified Curl Leaf]. Contamination by residual soil residues remaining on field after harvest was also examined by reseeding the circular plot with parsley. Atmospheric residues detected downwind on resin and filters indicated DCPA moved off‐target as a vapor as well as on particles both daring and up to 21 d after application. Volatilization flux, measured using the aerodynamic method, reached a maximum rate of 5.6 g ha−1h−1. An estimated 10% of the DCPA applied was lost to the atmosphere within 21 d of application. Deposition of DCPA outside the circular plot was evidenced by residues found on potted parsley plants and soil set out up to 23 m from the treated area. Parsley, seeded around the circular plot at the time of application and sampled 63 d later, contained residues ranging from 51 to 250 µg kg−1 indicating DCPA continued to move off‐target in air up to 60 d after application. The mass of DCPA in soil exhibited a log‐linear decline from which a 50 d dissipation half‐life was calculated. Parsley planted in the circular plot after the onion harvest did not contain DCPA residues when sampled 217 and 336 d after the original application. Results indicated that drift during, and volatilization and subsequent atmospheric transport after, application are potentially important sources of DCPA contamination occurring on nontarget crops in California.

Effect of Temperature, Moisture, and Soil Texture on DCPA Degradation

AbstractTurf managers sometimes experience poor or early loss of control of targeted weeds, even when herbicides are applied at recommended rates. This study was conducted to determine the influence of soil temperature and moisture on the rate of DCPA (dimethyl tetrachloroterephthalate) degradation in soil. The effect of six soil temperatures, three soil moistures, and three soil textures on the degradation of DCPA was measured in the laboratory through HPLC analysis. Soil temperature influenced the rate of DCPA degradation in the following order: 10<<15<<20<25=30>35°C. The average half‐life ranged from 92 d at 10°C to 18 d at 30°C. Soil moisture content influenced the rate of degradation in the following order: low (0.1 kg H2O kg−1 soil)≤ medium (0.2 kg H2O kg−1 soil) = high (0.4 kg H2O kg−1 soil). The average half‐life values of DCPA were 49, 33, and 31 d for the low, medium, and high soil moisture levels, respectively. A mathematical model of DCPA loss was utilized to determine the relative contribution of time, soil moisture, and soil temperature to the rate of degradation. Faster degradation of DCPA was observed from a sand/soil moisture (47.5:52.5, w/w) than from either a sand or a soil (Flanagan silt loam [fine, montmorillonitic, mesic Aquic Argiudoll]). It was concluded that the dissipation rate of DCPA is largely dependent on soil environmental conditions including soil temperature, soil moisture, soil texture, and the time interval since the application to the soil. Thus, it is suggested that soil environmental factors be considered in determining the timing of second or subsequent applications when necessary rather than following a fixed application schedul

Chemical Weed Control in Gypsophila

Abstract Postemergence and preemergence herbicides were evaluated for crop phytotoxicity and weed control in seepage-irrigated ‘Bristol Fairy’ gypsophila (Gypsophila paniculata L.). DCPA, napropamide, pronamide, and oryzalin were severely injurious to gypsophila. Metolachlor, oxyfluorfen, alachlor, and oxadiazon provided varying degrees of weed control and did not reduce plant vigor or yield. Best weed control was provided by two applications of 4.48 kg·ha-1 oxadiazon. Chemical names used: dimethyl tetrachloroterephthalate (DCPA); 2-(napthoxy)-N, N-diethylpropionamide (napropamide); 3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide (pronamide); 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide (alachlor); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one (oxadiazon).

Fenoxaprop-ethyl for Postemergence Crabgrass Control in Kentucky Bluegrass Turf

Abstract Fenoxaprop-ethyl at rates of 0.09 to 0.28 kg·ha−1 provided effective smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl.] control with minor injury to ‘Baron’ Kentucky bluegrass (Poa pratensis L.). Optimum timing for application was the 4-leaf to 5-tiller stage of crabgrass growth. At this stage of growth, fenoxaprop-ethyl applied at 0.20, 0.28, or 0.38 kg·ha−1 provided excellent (90% or better) season-long crabgrass control. Fenoxaprop-ethyl at 0.09 kg·ha−1 was an effective crabgrass control treatment at 2 to 4 leaf stage when combined with DCPA at 11.76 kg·ha−1. Split applications of fenoxaprop-ethyl in June and July at both 0.14 + 0.14 and 0.28 + 0.28 kg·ha−1 also provided season-long crabgrass control. Chemical names used: (±)-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate (fenoxaprop-ethyl); and dimethyl tetrachlo-roterephthalate (DCPA).

Establishment and Rooting of Zoysiagrass (Zoysia japonica) as Affected by Preemergence Herbicides

Preemergence applications of herbicides were evaluated for their effect on establishment of zoysiagrass (Zoysia japonicaSteud.) 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.

Organochlorine chemical residues in bluegills and common carp from the irrigated San Joaquin Valley Floor, California

Samples of bluegills (Lepomis macrochirus) and common carp (Cyprinus carpio) collected from the San Joaquin River and two tributaries (Merced River and Salt Slough) in California were analyzed for 21 organochlorine chemical residues by gas chromatography to determine if pesticide contamination was confined to downstream sites exposed to irrigated agriculture, or if nonirrigated upstream sites were also contaminated. Residues ofp,p′-DDE were detected in all samples of both species. Six other contaminants were also present in both species at one or more of the collection sites: chlordane (cis-chlordane +trans-nonachlor);p,p′-DDD;o,p′-DDT;p,p′-DDT; DCPA (dimethyl tetrachloroterephthalate); and dieldrin. Concentrations of most of these residues were generally higher in carp than in bluegills; residues of other compounds were found only in carp: α-BHC (α-benzenehexachloride), Aroclor® 1260, and toxaphene. Concentrations of most organochlorines in fish increased from upstream to downstream. Water quality variables that are influenced by irrigation return flows (e.g., conductivity, turbidity, and total alkalinity) also increased from upstream to downstream and were significantly correlated (P < 0.05) with organochlorine residue levels in the fish. In carp, concentrations of two residues-⌆DDT (p,p′-DDD +p,p′-DDE + +p,p′-DDT; 1.43 to 2.21 mg/kg wet weight) and toxaphene (3.12 mg/kg wet weight)-approached the highest levels reported by the National Pesticide Monitoring Program for fish from other intensively farmed watersheds of the United States in 1980 to 1981, and surpassed criteria for whole-body residue concentrations recomended by the National Academy of Sciences and National Academy of Engineers for the protection of piscivorous wildlife.

Response of Statice to Selected Herbicides

Abstract Seventeen herbicide treatments applied pre- and posttransplant were evaluated for toxicity to statice (Limonium sinuata L.) in 2 screening experiments. From these, 6 treatments were selected for further evaluation. Two applications (one pre-transplant followed by one posttransplant over the top) of 1.7 kg/ha alachlor, 4.5 kg/ha oxadiazon, 3.4 kg/ha EPTC, 9.0 kg/ha DCPA, 2.2 kg/ha napropamide, and 2.2 kg/ha oryzalin were evaluated for toxicity to field-grown ‘Midnight Blue’ statice. Oxadiazon, EPTC, and DCPA were not injurious to statice and produced yields of marketable panicles that were comparable to those in the untreated weed-free checks. Alachlor, napropamide, and oryzalin stunted plants and resulted in low panicle yields. Chemical names used: 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide (alachlor); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one (oxadiazon); S-ethyl dipropylthiocarbamate (EPTC); dimethyl tetrachloroterephthalate (DCPA); 2-(naphthoxy)-N,N-diethylpropionamide (napropamide); 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin).

Effect of perforated plastic row covers on residues of the herbicide DCPA in soil and broccoli.

Various types of clear or tinted, perforated plastic films are increasingly used as crop row covers in production of numerous fruit and vegetable crops (Rickard 1979). In temperate climates the modified environment under these covers permits earlier planting and promotes early-season growth but it also favors aggressive weed growth necessitating the use of herbicides. DCPA (dimethyl tetrachloroterephthalate, tradename Dacthal) is a post-plant, soil-applled herbicide that is widely used in many horticultural crops. DCPA is acknowledged as being strongly adsorbed to soll organic matter and essentially immobile in soll (Helling et al. 1971). It is degraded by soll microorganisms (Tweedy et al. 1968) and is not being appreciably affected by photodecomposition or volatilization (Weed Scl. Soc. Amer. 1983). However, recent studies have reported significant volatilization losses of DCPA following soll surface applications in the field (Glotfelty et al. 1984). Plastic row covers promote plant growth by maintaining increased temperature, humidity, C02, and higher levels of soll moisture (Rickard 1979). Some of these factors are likewise known to influence DCPA dissipation in soils (Glotfelty et al. 1984, Horowitz et al. 1974, Walker 1978). The purpose of this investigation was to determine how the use of several types of plastic row covers influenced residues of DCPA in soils and crops. Broccoli was used as a test crop because of the relatively short interval of time between herbicide application and harvest.

Effect of Soil pH, Fertility, and Herbicides on Weed Control and Quality of Bermudagrass (Cynodon dactylon) Turf

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.

Growth Inhibition and Disruption of Mitosis by DCPA in Oat (Avena sativa) Roots

One to 5.6 μM DCPA (dimethyl tetrachloroterephthalate) inhibited oat (Avena sativaL. ‘Victory’) root growth within 12 to 18 h. Treated roots were severely stunted and swollen. An analysis of cell division in roots treated with DCPA revealed a disruption of normal mitosis after prophase. Metaphase, anaphase, and telophase division figures were absent 8 to 10 h after treatment with 5.6 μM DCPA. In contrast, a 24-h treatment with 5.6 μM DCPA was necessary to eliminate prophase division figures. The number of aberrant division figures increased concomitantly with the reduction in normal division figures. The predominant type of aberrant division figure was a condensed prophase. When the aberrant division cycle was completed and cells entered interphase, the dispersed chromosomes coalesced to form large, polymorphic nuclei and, occasionally, micronuclei. Approximately 60% of the outer four tiers of cells in roots treated with 5.6 μM DCPA developed abnormal cell walls. These data suggest that DCPA causes root growth inhibition by disrupting several processes involving organized microtubules.

Weed Control in Azaleas Grown in Raised Field Beds

Abstract Two annual applications of oxyfluorfen (2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene), oxadiazon (2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one) or prodiamine (2,4-dinitro-N3,N3-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine) at 4.5 kg/ha controlled 80% of the weeds in several cultivars of newly-planted or established azaleas. Significant early season injury was observed in 1980 on ‘Hershey Red’, ‘Hinocrimson’, and ‘Delaware Valley White’ azaleas treated with DCPA (dimethyl tetrachloroterephthalate) at 11.2 kg/ha. Established ‘Hinocrimson’ azaleas treated with oxyfluorfen at 4.5 kg/ha were significantly larger than the control plants at the end of these experiments.

Goosegrass (Eleusine indica) Control in Turf in the Transition Zone

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 phosphorodithioateS-ester withN-(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.

Summer Squash Tolerances to Selected Herbicides

Abstract Dinoseb (2-sec-butyl-4,6-dinitrophenol), chloramben (3-amino-2,5-dichlorobenzoic acid), ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl) benzenamine], napropamide (2-(α-naphthoxy)-N,N-diethylpropionamide), DCPA (dimethyl tetrachloroterephthalate), and a tank mixture of bensulide [O-O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl) benzenesulfonamide] plus naptalam (N-1-naphthylphthalamic acid) were evaluated for weed control and tolerance of yellow straightneck, crook neck, and zucchini summer squash (Cucurbita pepo L.). Throughout the growing season, napropamide was most injurious to all cultivars. Napropamide resulted in unacceptable injury to young seedlings, and generally reduced early and total yields. DCPA and ethalfluralin treatments were consistently nonphytotoxic. Broadleaf weed control was not acceptable with any treatment due to the lack of control of smallflower galinsoga (Galinsoga parviflora Cav.). Ethalfluralin and napropamide were very effective in controlling annual grasses.