RESPONSE OF YELLOW NUTSEDGE,FLORIDA PUSLEY,AND PEANUTS TO THIOCARBAMATE HERBICIDES AS AFFECTED BY METHOD OF PLACEMENT IN SOIL*

Summary. Thiocarbamate herbicides were applied with incorporation devices and new subsurface application equipment on loamy sand at Tifton, Georgia, U.S.A. Subsurface-applied ethyl N,N-dipropylthiolcarbamate (EPTC), S-propyl bulylethylthiocarbamate (pebulate), and S-propyl dipropylthiocarbamate (vernolate) generally gave better control of Cyperus esculentus L. and Richardia scabra St Hil, but injured peanuts more than applications made on the soil surface and then incorporated into the soil. For soil incorporation, the power-driven rotary hoe was generally better than a disc harrow. Depth of subsurface placement critically affected herbicidal activity, especially on Cyperus esculentus; placement 1·5 in. below the soil surface gave more effective control than placement at 5·5 in. Réactions de Cyperus esculentus, de Richardia scabra et de l'arachide mix herbicides à base de thiocarbamate, en relation avec la methode de placement dans le sol     

Control of purple nutsedge (Cyperus rotundus) in cotton with benfuresate

The herbicide benfuresate applied preplanting to cotton (Gossypium hirsutum L.) fields infested with purple nutsedge (Cyperus rotundus L.) inhibited nutsedge growth for several weeks and was found selective for cotton. The best nutsedge control was achieved when the herbicide was mechanically incorporated following a preplant broadcast or band application which was activated by a sprinkler irrigation. The rate of benfuresate needed for effective and selective nutsedge control in cotton ranged from 0.80 to 1.60 kg/ha, the higher rates necessary in soils with higher clay and organic matter contents.     

Problems of herbicide assessment in peanuts in Jamaica

Delays of 40 or 60 days in weeding peanuts (Arachis hypogaea L.) gave lower yields and fewer pods per plant but did not affect seed number per pod. Yield, pod number per plant, seeds per pod and mean weight per seed were all less in unweeded plots. In three herbicide trials crop yields were not closely correlated with crop vigour scores made several weeks before crop maturity, or with weediness scores. Correlations between yields and weed dry weights were better, but certain high-yielding herbicide treatments gave poor weed control and in some cases had low crop vigour scores. Most yield differences reflected differences in pod number per plant, with additional smaller compensating or additive effects on the other components. Certain herbicides apparently gave high mean seed weights without diminishing seed numbers per pod. Pre-emergence alachlor was the most promising herbicide, combined with preplant incorporated vernolate if nutgrass was serious. Napropamide and metobromuron merit further testing.     

60．8％异丙甲·乙氧·扑草净EC防除花生田杂草的效果

采用田间试验测定了60．8％异丙甲·乙氧·扑草净乳油（ EC）在花生田的除草效果及其对花生的安全性。结果表明：用该药剂在花生播后苗前进行土壤处理,对马唐、鸭跖草、马齿苋、藜等具有很好的效果,推荐使用剂量1368～1824 g/hm2,药后45 d的杂草株防效为81．73％～83．69％,鲜质量防效为81．77％～84．93％。此外发现,该药剂对花生具有较高的安全性,处理区花生未见叶片黄化、畸形或苗株矮化等药害症状。与空白对照相比,施用60．8％异丙甲·乙氧·扑草净EC后增产显著,同时增产效果优于对照药剂乙草胺,说明60．8％异丙甲·乙氧·扑草净EC对花生安全,且除草、增产效果显著。     

Factors affecting benfuresate activity against purple nutsedge (Cyperus rotundas L.)

Benfuresate (2-3-dihydro-3,3-dimethylbenzofu-ran-5-yl ethanesulfonate) is a selective herbicide for the control of purple nutsedge in cotton. Under outdoor conditions, purple nutsedge was sensitive to benfuresate incorporated in soil up to eight days after initiation of shoot sprouting from the tuber. Older seedlings recovered from the damage. During the period of susceptibility to benfuresate, young shoots more sensitive than the roots. Under controlled environmental conditions, benfuresate applied directly to apical buds developing from the tuber caused severe damage to the treated bud and induced abrupt development of axillary buds. Negligible amounts of the applied herbicide were translocated from the treated part to the other buds and roots. Application of the herbicide to fully developed leaves had no effect, probably because of its rapid metabolism and low basipetal mobility. Its relatively high volatility may also contribute to its low foliar post-emergence activity. Tubers also absorbed herbicide vapours. Root uptake of ¹⁴C-benfuresate resulted in a rapid accumulation of ¹⁴C in the shoot, which had no effect on the purple nutsedge plant, regardless of concentration. The herbicide is rapidly converted, mainly to a non-phytotoxic polar product. These results may explain the high sensitivity of the weed to benfuresate at early growth stages, and the lack of sensitivity in mature plants.     

Accelerated degradation of thiocarbamate herbicides in Israeli soils following repeated use of vernolate

Accelerated degradation of vernolate, EPTC and butylate but not of cycloate was detected in soils from three locations in Israel which were treated annually with vernolate. Repeated application of EPTC to soils with and without a history of vernolate application, under laboratory conditions, resulted in a progressive increase in its rate of dissipation with each application. Accelerated degradation of EPTC was also rapidly induced by mixing small amounts (5%) of soil with a history of vernolate treatment with soil that had never received vernolate. Liberation of ¹⁴CO₂ from [¹⁴C]EPTC was more rapid in vernolate-treated soils than in untreated soils, indicating a development of microbial populations in soil capable of rapidly degrading the EPTC. Degradation of [¹⁴C]EPTC was faster in soil previously cropped with maize than in non-cropped soil, but slower in soils cropped with cotton or peanuts.     

Dissipation and movement of flumioxazin in soil at four field sites in Chile

BACKGROUND: Flumioxazin is a soil-applied herbicide recommended for broadleaf weed control in soybeans and peanuts, and was recently introduced for vineyard weed management. Considering the limited information available in relation to flumioxazin field soil behaviour, the main objectives of this study were to determine the persistence, adsorption and movement of flumioxazin in soil in four Chilean vineyard production areas. RESULTS: DT(50) values ranged from 10.6 +/- 1.0 to 32.1 +/- 3.1 days between localities, being correlated with rain events, time between herbicide application and first heavy rain event, and soil pH. Flumioxazin soil residue found at 90 days after application (DAA) varied from 9.6 to 24.9% of the initial amount applied, and depended on the total rainfall amount that occurred during the first 90 DAA. Herbicide leaching below 15 cm was approximately 45% of the flumioxazin detected at 90 DAA in the whole soil profile. Flumioxazin maximum leaching soil depth was 45 cm at all locations. K(d) values varied from 2.54 to 6.51 mg L(-1), depending on localities and soil profile depth, and correlated positively with organic carbon and clay content. CONCLUSIONS: These results indicate that flumioxazin is a herbicide with low environmental risk owing to its short DT(50), reduced soil residues 3 months after application and low effective dose.     

SHOOT ZONE UPTAKE OF SOIL-APPLIED HERBICIDES IN PISUM SATIVUM L.

Summary. The effects of localized herbicide placement at different internodes of pea ( Pisum sativum L. cv. Alaska) shoots below the soil surface after plant emergence were studied by removing the soil from around the shoots and replacing with herbicide-treated soil. The first internode proved insensitive to linuron, diuron, atrazine and simazine at 4·5 kg/ha, while treatment of the second and third internodes markedly reduced plant growth 4–6 days after treatment. Separate exposure of the first internode alone, and the second and part of the third together to ¹⁴C-labelled atrazine indicated no difference in herbicide metabolism. However, a two- to threefold increase in ¹⁴C uptake and movement to the foliar parts occurred when the second and part of the third internode was treated, as compared to first internode treatment. Thus the differential sensitivity of the internodes to atrazine, and possibly to the other herbicides, may be because the more mature first internode allows less uptake and subsequent movement to the foliar parts.
Absorption dans la zone des tiges des herbicides appliqués dans le sol chez Pisum sativum L.     

Sodium 2,2,3,3-tetrafluoropropionate,a New Herbicide for Jute Field Weeds

Abstract

Sodium 2,2,3,3-tetrafluoropropionate (TFP) was tested as pre-planting and post-emergence applications on jute heavily infested with grasses and sedges. The herbicide was applied by two methods, at several rates and at different times before sowing. As a post-emergence application it was sprayed over a three week old crop. The best results were obtained when the herbicide was incorporated into the soil ten days before sowing at 3–4 kg a.i./ha. This practice controlled all grasses and sedges except nutsedge, which was only reduced by 30–40%, although higher rates gave better control. No phytotoxic effects on jute were observed with this rate and method of application.     

Distribution and efficacy of drip-applied metam-sodium against the survival of Rhizoctonia solani and yellow nutsedge in plastic-mulched sandy soil beds

The effects of metam-sodium application rate on soil residence time, spatial and temporal distributions of methyl isothiocyanate and pest control efficacy were studied in a Georgia sandy soil. Metam-sodium 420 g L(-1) SL was drip applied at rates of 147 and 295 L ha(-1) in plastic-mulched raised beds. Methyl isothiocyanate concentrations in soil air space were monitored from four preselected sites: 10 and 20 cm below the emitter, and 20 and 30 cm laterally away from the emitter at 3, 12, 24, 48, 72, 120 and 240 h after chemigation. A higher rate of metam-sodium application resulted in higher methyl isothiocyanate concentrations in the soil. Highest methyl isothiocyanate concentrations were found at 20 cm below the emitter, and lowest at 30 cm laterally away from the emitter. Methyl isothiocyanate concentrations decreased with time and distance from the emitter. Lower methyl isothiocyanate concentration x time product values at 20 and 30 cm away from the emitter resulted in lower mortalities of Rhizoctonia solani Kühn and yellow nutsedge (Cyperus esculentus L.). The results demonstrated that methyl isothiocyanate can be delivered at lethal doses with drip-applied water downward within the beds. Lateral diffusion of methyl isothiocyanate from the point of application did not reach biologically active concentrations to affect the survival of R. solani or yellow nutsedge. Further studies on the lateral distribution of methyl isothiocyanate in sandy soils are needed to circumvent this limitation.     

CHEMICAL FALLOW CONTROL OF NUTSEDGE

Summary. Field experiments were conducted to find a herbicide for complete control of nutsedge ( Cyperus rotundus L.). We applied seventeen herbicides and some of their combinations as chemical fallow. EPTC and CP-31675 (6- tert -butyl-2-chloro-o-acetotoluidide) gave good but only temporary control of nutsedge. Dichlobenil at 2·5 or 5 lb/ac gave fair control for 1 year. Rates of 10 or 20 lb/ac of dichlobenil controlled nutsedge completely for 1 year but severely reduced the yield of oats planted 5 months after application. The highest rate completely killed tubers and prevented reinfestation for 1 year. Analyses indicated no residue of dichlobenil or of its metabolite, 2,6-dichlorobenzoic acid, in vegetative parts and seeds of oats planted 5 months after application of 2.5, 5 or 10 lb/ac of dichlobenil. At equivalent rates the herbicide TH-073-H (N-hydroxymethyl-2,6-dichlorothiolbenzamide) gave control of nutsedge similar to that with dichlobenil. The combinations of 8 lb/ac amitrole-T and 10 lb/ac dichlobenil or TH-073-H were just as effective in controlling nutsedge shoots and tubers as dichlobenil or TH-073-H applied alone. The mixture of dichlobenil plus CP-31675, each at 5 lb/ac, gave excellent control of nutsedge and tubers for 1 year. The herbicides terbacil ( 3-ter -Nbutyl-5-chloro-6-methyluracil) or Du Pont 733 ( 3-tert -butyl-5-bromo-6-methyluracil) at 10 lb/ac provided almost complete control of nutsedge. Application of terbacil to plants aged 4–6 weeks gave better results than application to mature nutsedge in the fall.
La lutte chimique contre le cypirus     

EFFECT OF DICAMBA ON OXYGEN UPTAKE AND CELL MEMBRANE PERMEABILITY IN LEAF TISSUE OF CYPERUS ROTUNDUS L.

Summary. The effect of the herbicidal compound dicamba (2-methoxy-3,6-dichlorobenzoic acid) on the rate of oxygen uptake and on cell membrane permeability of leaf tissues of purple nutsedge ( Cyprus rotundus L.) was studied. Dicamba induced noticeable alterations in both the pattern of oxygen consumption and in permeability of the cells following spraying of the foliar parts of the plants. A pronounced decrease in respiratory rate was observed 5 days after treatment with 10⁻³ M dicamba, but the rate of oxygen uptake rose to approximately the level of the control 10 days after application of the herbicide. Permeability of the cell membranes decreased 5 days after treatment of the leaves with 10⁻² M or 10⁻³ M dicamba. The results indicate that the early disruption of the cell membranes might be related to the mode of action of the herbicide.     

Biological activity of dinitramine in soils

In pot studies with dinitramine the susceptibility of French bean (Pltaseolus vulgaris L.) seedlings to the herbicide was influenced by the depth of sowing the seed and the dose and depth of incorporation of the herbicide. Maximum phytotoxicity occurred when the seeds of French bean were sown into a zone in which dinitramine had been incorporated. Where the seeds were separated from the herbicidetreated zone by a layer of untreated soil, the susceptibility of the French bean seedlings increased with increasing depth of sowing. The greater the distance between the point of contact with the herbicide and the soil surface the greater was the injury. Dinitramine is active in the vapour phase, and volatilization and bioactivity were directly related to concentration and inversely related to depth of incorporation and of placement in the soil.     

Interaction between timings and doses of quindorac in rice

Quinclorac (3,7-dichloro-8-quinolinecarboxylic acid) is a new herbicide in United States rice production. Field studies were conducted in 1990 and 1991 in Mississippi to determine the influence of application timings and rates on weed control efficacy and rice yield. Control of Echinochloa crus-galli (L.) Beauv. (barnyard-grass), Sesbania exaltata (Raf.) Rydb. ex A. W. Hill (hemp sesbania) and Ipomoea wrightii Gray (palmleaf morning glory) were greatest with early post-emergence application. Efficacy of pre-emergence application depends strongly on soil moisture, with significantly reduced weed control resulting when applied to dry soil. Weed control with pre-emergence application to moist soil was comparable with early post-emergence application at higher rates of quinclorac. Pre-plant and incorporated quinclorac controlled weeds effectively. Control of E. crus-galli, S. exaltata and I. wrightii ranged from 73 to 99%, 75 to 99%, and 92 to 99% at 28 days after treatment, respectively. Rice yield generally reflected weed control. No rice injury was observed for any treatment. Results indicate that early post-emergence application of quinclorac is the best time for using reduced rates and field conditions at application should be considered with these rates pre-emergence.     

Dissipation of imazapyr, flumetsulam and thifensulfuron in soil

The degradation of imazapyr, flumetsulam and thifensulfuron applied at 500.40 and 30 g active ingredient (a.i.) ha^-1, respectively, to silt loam soil was studied under laboratory and field conditions. Herbicide residues were analysed by a lentil ( Lens culinarits L.) bioassay. Results showed that temperature had a significant effect on herbicide degradation, whereas the impact of soil organic matter ami pH were less well defined. Half-lives for imazapyr, flumetsulam and thifensulfuron in soil samples from the 0-5 cm layer (6.4% organic carbon) at 15 °C were 125, 88 and 5.4 days, respectively, and 69, 30 and 3.9 days at 30°C. In soil sampled from the 15-20 cm layer (3.5% organic carbon) half-lives were 155. 70 and 6.4 days, respectively, at 15 °C and 77, 24 and 4.8 days at 30 °C, A field experiment investigated the degradation and teaching of each herbicide under two precipitation regimes [natural precipitation (208 mm), and natural precipitation plus 75 mm irrigation (283 mm) over 4 months to a soil depth of 25 cm. Thifensulfuron degraded rapidly, whereas residues of flumetsulam and imazapyr leached below 25 cm in both the low-and high-precipitasion treatments after 4 months. Significant imazapyr residues were still present in the soil to 25 cm depth after 3 months, A multi-component model for herbicide dissipation was developed and evaluated using data from the laboratory and field experiments.     

Growth and reproduction of Cyperus esculentus L. and Cyperus rotundus L.

The growth of both species (as characterized by their total dry weight, inflorescence dry weight, root and rhizome dry weight and number of shoots per pot) was similar, but they differed in the manner in which the dry weight was partitioned to reproductive structures. Each species partitioned less than 2% of its dry weight into floral formation. However, yellow nutsedge (Cyperus esculentus L.) partitioned only 28% of its dry weight to tubers, whereas purple nutsedge (C. rotundus L.) partitioned 50% of its dry weight to fewer and larger tubers. The allocation of dry weight to reproductive structures was related to changes in day-length. Yellow nutsedge tuber formation increased as day-length decreased from 14.5 to 12.5 h, while floral formation did not begin until the day-length dropped below 14 h. Purple nutsedge formed inflorescences earlier and production continued throughout the remainder of the study, but tuber formation was curvilinear and accelerated as the day-length decreased.     

Influence of environmental factors on the performance of sethoxydim against Elymus repens (L.)

The performance of sethoxydim on Elymus repens (L.) Gould was studied under contrasting levels of humidity, light intensity, temperature, soil moisture and simulated rainfall using controlled environment chambers. Over a 24-h post-spraying period, increases in humidity and temperature markedly enhanced herbicide performance, while effects of light intensity were less pronounced. Soil moisture deficit significantly reduced herbicide performance, but there were no adverse effects of wet soil conditions (twice field capacity) on activity. The effects of simulated rain depended upon herbicide dosage, time interval between spraying and the onset of rain, and rain intensity. A low rain intensity of 0.5 mm h^?1 did not reduce herbicide performance even when applied 10 min after spraying. The longer term studies, over 4 weeks, showed increases in herbicide activity with higher temperatures but lower light intensities.     

360g／L吡氟·氟噻·呋草酮悬浮剂对冬小麦田杂草的防除效果及对后茬作物的安全性

为明确360g／L吡氟·氟噻·呋草酮悬浮剂在小麦田的应用前景,采用田间小区试验方法,观察其对小麦田主要杂草的控制作用和对小麦及后茬作物玉米、大豆、花生的安全性。结果表明：360g／L吡氟·氟噻·呋草酮悬浮剂对小麦田主要杂草猪殃殃、蔺草、硬草、播娘蒿等一年生杂草均有好的防除效果,随用药量的增加防效逐渐提高;药后180d株防效和鲜重防效均在90％以上,优于异丙隆常规剂量处理,显著提高了小麦的产量;药后226d的土壤残留对后茬作物玉米、大豆、花生安全,对其苗期生长及产量无不良影响。     

Gibberellin influence on membrane disruption by thiocarbamate herbicides

Vernolate (0, 8, 16, 31, 62, 125.0, or 250.0 ppbw) incorporated into sand inhibited the growth of wheat (Triticum aestivum L. cv Holley) at 125.0 ppbw. These growth inhibition and morphological responses were virtually identical to wheat response to EPTC at 125 ppbw. ¹⁴C from vernolate (carbonyl labeled) (125.0 ppbw) was absorbed into wheat seedlings at approximately 1.8 μM on the presumption that the ¹⁴C present was [¹⁴C]vernolate. Since the response of wheat to the thiocarbamate herbicides resembles a gibberellic acid (GA) deficiency and cell enlargement requires the presence of functional plasmalemmas and tonoplasts, the question of membrane disruption by excessive concentrations of thiocarbamate herbicides and potential reversal thereof by GA₃ was studied by measuring the efflux of K⁺, Na⁺, and Mg²⁺. GA₃ (0.003 μM) stimulated lettuce leaf disc growth in diameter and fresh weight. This GA-stimulated increase in size and weight was reversed by 1 mM EPTC. Betacyanin efflux from beet leaf tonoplasts was increased by 1 mM EPTC and this efflux was not reversed by exogenous GA₃ (0.3 μM). This influence by supraoptimal EPTC concentrations was shown to be via membrane disruption, which obviated any possible GA influence by eliminating the functionality of the membranes requisite to the development of a GA response. It is concluded that viable mode-of-action studies must measure physiological responses consistent with the symptomology of herbicide responses normally observed with each herbicide at field concentrations.     

Effect of glyphosate on the sprouting of Cyperus rotundus L. tubers

Post-emergence applications of glyphosate [N-(phosphonomethyl)glycine] have been shown not to eradicate purple nutsedge (Cyperus rotundus L.) in the field. It was not known if this was due to failure to control emerged plants or if dormant tubers produced new plants after application. Studies with individual plants were conducted in screenhouse facilities to determine the effects of glyphosate rate, time for translocation, area of foliage treated, and shade on the sprouting ability of tubers attached to treated plants. Rates of 1.5–2.0 kg/ha glyphosate inhibited tuber sprouting; 72 h were required for complete translocation at 1.0 kg/ha whereas 36 h were sufficient at 2.0 kg/ha. Treating less than all of the foliage reduced foliar control and increased tuber sprouting. Shading treated plants reduced control of the foliage but did not affect glyphosate translocation to the tubers. These studies showed that glyphosate kills C. rotundus foliage and the tubers attached to treated plants. Therefore, regrowth after glyphosate application under field conditions is due to dormant tubers which sprout after treatment.