Postemergence Treatments Research Articles

Synthesis and herbicidal activity of N-(2,2-dimethyl-7-alkoxy-2,3-dihydrobenzofuran-5-yl)-2-(4-arylxoyphenoxy)propionamides

In order to find novel herbicidal active compounds, a series of N-(2,2-dimethyl-7-alkoxy-2,3-dihydro-benzofuran-5-yl)-2-(4-arylxoyphenoxy)propionamides was designed, prepared and evaluated for their herbicidal activity. Bioassay results showed that most of the title compounds had excellent and selective herbicidal activity against the monocotyledonous grasses. In particular, compounds 1g and 1m showed 100% inhibition against the growth of three monocotyledonous grasses under both postemergence and preemergence treatments at the dose of 2250 g/hm2 (1 hm2=104 m2), and could be used as lead compounds for further development of novel potential herbicidal agents.

Synthesis, Crystal Structure and Herbicidal Activity of N-(Thiazol-2-yl)-2-(4-aryloxyphenoxy) propionamides

Eighteen N-(thiazol-2-yl)-2-(4-aryloxyphenoxy)propionamides were synthesized by reaction of (R)-(+)-2-(4-hydroxyphenoxy)propanoyl chlorides with 2-aminothiazole derivatives. Their structures were confirmed by H NMR, C NMR, elemental analysis, EI-MS and optical rotation. The crystal structure of (R)-N-(4-trifluoromethyl-5-ethoxycarbonylthiazole-2yl)-2-[4-(3-fluoro-5-chloropyridin-2-yl)oxy)phenoxy)propionamide was determined by X-ray diffraction analysis. The crystal belonged to the tetragonal system, space group P41212 with a=14.45502(18) A, b=14.45502(18) A, c=21.7813(5) A; Z=8, V=4551.14(15) A, Dc=1.558 Mg/m, F(000)=2176, μ=3.013 mm , and the final R=0.0302, wR=0.0687. The bioassay results indicated that most of title compounds displayed moderate to excellent herbicidal activity against crabgrass (Digitaria sanguinalis) and barnyard grass (Echinochloa crusgalli.) at the dose of 1500 g/hm. Some compounds showed 100% inhibition against the growth of the crabgrass and barnyard grass when applied at the pre-emergence and post-emergence treatment.

Strip Tillage and Early-Season Broadleaf Weed Control in Seeded Onion (Allium cepa)

Field experiments were conducted in 2007 and 2008 near Oakes, North Dakota (ND), USA, to evaluate if strip tillage could be incorporated into a production system of seeded onion (Allium cepa) to eliminate the standard use of a barley (Hordeum vulgare) companion crop with conventional, full width tillage, yet support common early-season weed control programs. A split-factor design was used with tillage (conventional and strip tillage) as the main plot and herbicide treatments (bromoxynil, DCPA, oxyfluorfen, and pendimethalin) as sub-plots. Neither tillage nor herbicide treatments affected onion stand counts. Common lambsquarters (Chenopodium album) densities were lower in strip tillage compared to conventional tillage up to three weeks after the post-emergence applied herbicides. In general, micro-rate post-emergence herbicide treatments provided greater early-season broadleaf weed control than pre-emergence herbicide treatments. Onion yield and grade did not differ among herbicide treatments because the mid-season herbicide application provided sufficient control/suppression of the early-season weed escapes that these initial weed escapes did not impact onion yield or bulb diameter. In 2007, onion in the strip tillage treatment were larger in diameter resulting in greater total and marketable yields compared to conventional tillage. Marketable onion yield was 82.1 Mg ha−1 in strip tillage and 64.9 Mg ha−1 in conventional tillage. Results indicate that strip tillage use in direct-seeded onion production was beneficial, especially when growing conditions were conducive to higher yields and that the use of strip tillage in onion may provide an alternative to using a companion crop as it did not interfere with either early-season weed management system.

Synthesis and herbicidal activity evaluation of novel α-amino phosphonate derivatives containing a uracil moiety.

A series of novel α-amino phosphonate derivatives containing a uracil moiety 3a-3l were designed and synthesized by a Lewis acid (magnesium perchlorate) catalyzed the Kabachnik-Fields reaction. The bioassays {in vitro, in vivo [Glass House 1 (GH1) and Glass House 2 (GH2)]} showed that most of compounds 3 exhibited excellent and selective herbicidal activities; for example, in GH1 test, compounds 3b, 3d, 3f, 3h and 3j showed excellent and wide spectrum herbicidal activities at the dose of 1000 g/ha, and compounds 3b and 3j exhibited 100% inhibition activities against the four plants in both post- and pre-emergence treatments. Moreover, most of compounds 3 showed higher inhibition against Amaranthus retroflexus and Digitaria sanguinalis than Glyphosate did in pre-emergence treatment. In GH2 test, the four compounds (3b, 3d, 3h and 3j) exhibited 100% inhibition against Solanum nigrum, Amaranthus retroflexus and Ipomoea hederacea in post-emergence treatment and displayed 100% inhibition against Solanum nigrum, Amaranthus retroflexus in pre-emergence treatment at the rate of 250 g/ha, and compound 3b showed the best and broad spectrum herbicidal activities against the six test plants. However, the four compounds displayed weaker herbicidal activities against Lolium perenne and Echinochloa crus-galli than the other four plants at the rate of 250 g/ha in both pre- and post-emergence treatments. So, compounds 3 can be used as a lead compound for further structure optimization for developing potential selective herbicidal agent. Their preliminary structure-activity relationships were also investigated.

Effect of fertility levels and herbicide mixtures on yield and yield attributes of rainfed maize under temperate conditions of Kashmir

The present study was aimed to assess the response of rainfed maize to various fertility levels and weed management practices under temperate Kashmir conditions. The field experiment consisted of 3 fertility levels of NPK viz., 60:40:20, 75:50:30 and 90:60:40, N:P2O5:K2O kg ha−1) and 4 weed management practices viz., no weeding, two hand weeding 20 and 50 days after sowing (DAS), atrazine @ 1.0 kg a.i. ha−1 (as preemergence) + one hand weeding 20 DAS, and atrazine @ 1.0 kg a.i. ha−1 (pre-emergence) + isoprotron @ 1.0 kg a.i. ha−1 (post-emergence). The results revealed that fertility levels of 90:60:40 and 75:50:30 (NPK) were at par and showed significant increase in cob length, cobs plant−1, grains cob−1, 100-seed weight, grain yield, biological yield and stover yield as against fertility level of 60:40:20 NPK. However, the number of rows cob−1 and cob diameter showed significant improvement with increase in fertility level. Increase in fertility level from 60:40:20 to 75:50:30 NPK significantly enhanced harvest index but further addition caused significant decrease. Weed management practices of atrazine as preemergence application + one hand weeding at 20 DAS was at par with atrazine as pre-emergence + isoprotron as post-emergence application treatment and both showed significant improvement in all yield contributing characters over no weeding and 2 hand-weedings at 20 and 50 days DAS. Both grain and stover yields were significantly higher with atrazine as pre-emergence application + 1 hand weeding at 20 DAS over hand weeding on 20 and 50 DAS and no weeding.

Synthesis and Biological Activities of Novel Cyanoacrylates Containing 1,3,4-Oxadiazole Moiety

In order to find new cyanoacrylate lead compounds, a series of novel cyanoacrylates carrying 1,3,4-oxadiazole moiety were prepared by the method of active substructure combination. The structures of the title compounds were characterized by 1 H NMR, 13 C NMR and elemental analysis. Preliminary bioassay data displayed that in postemergence treatment compound 8b had 80% herbicidal activity against Stellaria media at 1500 g/ha and compound 8j showed 70% herbicidal activity against Chenopodium serotinum L. at 1500 g/ha. Additionally, compounds 8e, 8k, 8m and 8n exhibited good anti-tumor activity against HepG2 cells with the IC50values of 8.2 μM, 5.9 μM, 8.0 μM 和 12.6 μM, respectively.

Selecting patterns and features for between- and within- crop-row weed mapping using UAV-imagery

This paper approaches the problem of weed mapping for precision agriculture, using imagery provided by Unmanned Aerial Vehicles (UAVs) from sunflower and maize crops. Precision agriculture referred to weed control is mainly based on the design of early post-emergence site-specific control treatments according to weed coverage, where one of the most important challenges is the spectral similarity of crop and weed pixels in early growth stages. Our work tackles this problem in the context of object-based image analysis (OBIA) by means of supervised machine learning methods combined with pattern and feature selection techniques, devising a strategy for alleviating the user intervention in the system while not compromising the accuracy. This work firstly proposes a method for choosing a set of training patterns via clustering techniques so as to consider a representative set of the whole field data spectrum for the classification method. Furthermore, a feature selection method is used to obtain the best discriminating features from a set of several statistics and measures of different nature. Results from this research show that the proposed method for pattern selection is suitable and leads to the construction of robust sets of data. The exploitation of different statistical, spatial and texture metrics represents a new avenue with huge potential for between and within crop-row weed mapping via UAV-imagery and shows good synergy when complemented with OBIA. Finally, there are some measures (specially those linked to vegetation indexes) that are of great influence for weed mapping in both sunflower and maize crops.

Evaluation of the side effects of poly(epsilon-caprolactone) nanocapsules containing atrazine toward maize plants.

Poly(epsilon-caprolactone) (PCL) nanocapsules have been used as a carrier system for the herbicide atrazine, which is commonly applied to maize. We demonstrated previously that these atrazine containing polymeric nanocapsules were 10-fold more effective in the control of mustard plants (a target species), as compared to a commercial atrazine formulation. Since atrazine can have adverse effects on non-target crops, here we analyzed the effect of encapsulated atrazine on growth, physiological and oxidative stress parameters of soil-grown maize plants (Zea mays L.). One day after the post-emergence treatment with PCL nanocapsules containing atrazine (1 mg mL−1), maize plants presented 15 and 21% decreases in maximum quantum yield of photosystem II (PSII) and in net CO2 assimilation rate, respectively, as compared to water-sprayed plants. The same treatment led to a 1.8-fold increase in leaf lipid peroxidation in comparison with control plants. However, all of these parameters were unaffected 4 and 8 days after the application of encapsulated atrazine. These results suggested that the negative effects of atrazine were transient, probably due to the ability of maize plants to detoxify the herbicide. When encapsulated atrazine was applied at a 10-fold lower concentration (0.1 mg mL−1), a dosage that is still effective for weed control, no effects were detected even shortly after application. Regardless of the herbicide concentration, neither pre- nor post-emergence treatment with the PCL nanocapsules carrying atrazine resulted in the development of any macroscopic symptoms in maize leaves, and there were no impacts on shoot growth. Additionally, no effects were observed when plants were sprayed with PCL nanocapsules without atrazine. Overall, these results suggested that the use of PCL nanocapsules containing atrazine did not lead to persistent side effects in maize plants, and that the technique could offer a safe tool for weed control without affecting crop growth.

Weed Management in Autumn Fresh Market Spinach: A Nonchemical Alternative

Physical rather than chemical treatments are preferred for integrated production and are required for organic production to ensure a sustainable production. Weed management in many horticultural crops is heavily constrained by the limited number of herbicides available. Physical weed control strategies, on the other hand, are essential to organic vegetable production and greatly assist conventional vegetable farmers. A physical weed control strategy was developed and compared with a standard chemical strategy within an integrated farming system in fresh market spinach (Spinacia oleracea). The experiment was conducted on a farm in the Serchio Valley (Tuscany, central Italy) in 2004 and 2005, where spinach is one of the most important crops. The physical weed control strategy consisted of a stale seedbed technique and postemergence treatments using various mechanical and thermal machines. The chemical weed control strategy consisted of a single postemergence herbicide treatment using phenmedipham at 15.8% in compliance with integrated production norms in Italy. Strategy performance was assessed in terms of weed density and biomass, total labor requirement, and crop yield. Compared with the chemical system, the physical system required a substantially larger labor input (19 vs. 6 h·ha−1), but like the chemical system, did not require hand weeding. In addition, the physical system reduced weed dry biomass at harvest by 50% and increased spinach fresh yield by 35%. Physical strategies therefore are a valid alternative to the use of herbicides in fresh market spinach and may be especially desirable given the increasing importance of nonchemical weed control in integrated, organic, and conventional farming systems in Europe and the United States.

Response of Aryloxyalkanoate Dioxygenase-12 Transformed Soybean Yield Components to Postemergence 2,4-D

New trait technology incorporating 2,4-dichlorophenoxyacetic acid (2,4-D) resistance in soybean provides an alternative method to control weeds. However, the effect of postemergence treatments of 2,4-D on aryloxyalkanoate dioxygenase-12 (AAD-12) soybean on injury and yield components has not been reported. Our objectives were to characterize the effect of 2,4-D (dimethylamine salt) rates (0, 1,120, and 2,240 g ae ha−1) and soybean growth stage (V5, R2, or V5 followed by R2) on AAD-12 soybean injury and yield components. Less than 3% soybean injury was observed when 2,240 g ha−1of 2,4-D was applied to R2 soybean, and less than 1% soybean injury was caused by 1,120 g ha−1of 2,4-D. Seed yield, seed mass, pod number, seed number, seed per pod, reproductive node number, pods per reproductive node, node number, and percent reproductive nodes were not affected by 2,4-D treatments when applied at the V5, R2, or the V5 followed by R2 soybean growth stage. This research demonstrates that soybean transformed with AAD-12 can tolerate foliar applications of 2,4-D at rates up to 2,240 g ha−1with no effect on soybean grain yield components.

Weed Control in Irrigated Corn with Combinations of Corvus, Balance Flexx, Capreno, Laudis, Harness, Atrazine, Glyphosate, Dual, and Diflexx

Most preemergence treatments followed by postemergence treatments provided better Palmer amaranth control than preemergence treatments alone or early postemergence treatments alone (Table 2). The better treatments provided good control of Palmer amaranth, kochia, Russian thistle, crabgrass, green foxtail, and shattercane. All treatments elevated yield over the untreated control.

Selective Herbicides for Cultivation ofEucalyptus urograndisClones

Competition control is essential for successful eucalyptus plantation establishment, yet few selective herbicides have been identified. Five herbicides, flumioxazin, imazamox, imazapic, oxyfluorfen, and sulfometuron methyl, were evaluated for selective weed control in the establishment of genetically modified frost tolerantEucalyptus urograndisclones. Herbicides were applied at two or three rates, either before or after weed emergence, and compared to a nontreated control and to near-complete weed control obtained with glyphosate directed sprays. Applications prior to weed emergence were most effective for weed control and, with the exception of imazapic, all resulted in enhanced eucalyptus growth relative to the nontreated control. Among postemergent treatments, only imazamox enhanced stem volume. Among selective herbicide treatments, preemergent 2240 g ha−1oxyfluorfen produced the best growth response, resulting in stem volume index that was 860% greater than the nontreated control, although only 15% of the volume index obtained with near-complete weed control. Imazapic was the most phytotoxic of all herbicides, resulting in 40% mortality when applied preemergent. Survival was 100% for all other herbicide treatments. This research found the previously nontested herbicides imazamox and imazapic to be effective for selective weed control and refined application rate and timing of five herbicides for use in clonal plantations.

Synthesis and Herbicidal Activity ofN-Acyl-N-(m-fluoro-benzyl)-6-amino-coumarin

以N-间氟苄基-6-氨基香豆素为先导,利用活性亚结构拼接原理,设计、合成了一系列N-酰基-N-间氟苄基-6-氨基香豆素衍生物,其结构用1H NMR、ESI-MS和元素分析表征,N-三氟乙酰基取代的化合物d5结构经X-ray单晶衍射进一步确证.采用琼脂小杯法和盆栽法对合成化合物的除草活性进行了初步研究.结果表明,100 mg/L分别为N-氯乙酰基、N-溴乙酰基、N-三氟乙酰基、N-（2,4-二氯苯氧乙酰基）取代的化合物d2,d3,d5和d17对反枝苋根、茎的抑制率大于75%,优于乙草胺EC;1500 g/ha分别为N-溴乙酰基、N-（2,4-二氯苯氧乙酰基）取代的化合物d3和d17对反枝苋等双子叶杂草茎叶处理的抑制率达76%以上;同剂量化合物d17对单子叶作物小麦、玉米和水稻安全.

Sequential Treatments of Rimsulfuron, Mesotrione, Thifensulfuron, Balance Flexx, Cinch, Cinch ATZ, and Prowl H2O Mixtures for Weed Control in Irrigated Corn

No treatment with less than 1.5 lb/a atrazine provided commercially acceptable Palmer amaranth control. The best level of Palmer amaranth control was produced by treatments that had good preemergence control augmented by a postemergence application with two or more modes of action that contained 0.5 lb/a atrazine. All treatments provided excellent kochia control. The best Russian thistle treatments provided from 77 to 88% control. The best foxtail or crabgrass treatments provided from 91 to 94% control. Combinations of preemergence treatments followed by a postemergence treatment achieved excellent shattercane control.

Effect of sequential application of metribuzin on selectivity and weed control in soybean

Post-emergence treatments are often the keys to efficient weed control, and could be a substitute or supplementary to pre-emergence treatment. Accordingly, this study was designed to test the selectivity and efficacy of sequential (pre- + post-emergence) applications of metribuzin on weeds in soybean, and to optimize the dose, volume rate and time of application. We observed that sequential metribuzin treatments were more toxic to soil micro-organisms and caused greater inhibition in photosynthesis, acetylene reduction activity and nodulation of soybean compared to only pre-emergence applications of metribuzin or pendimethalin. The negative effects, however, were mitigated by increased activities of superoxide dismutase and ascorbate peroxidase in soybean. The sequential applications left negligible residues at harvest. A sequential application of metribuzin 0.25 kg ha−1 2 days after sowing and 0.1 kg ha−1 20 days after sowing with 200 Lha−1 of water gave a higher seed yield. This ensured the possibility of sequential application of metribuzin with an optimized dose, volume rate and time of application.

Researches regarding weed control in soybean crop

Soybean shows special sensitivity to weeding while in the early growth stages until the land is covered, but also in the mature stages after the leaves begin to fall. Once invaded by weeds, especially in the first phase of growth, the culture is no longer recovering even if later, weeds are controlled. The purpose of presented paper is to identify an integrated weed control system for the soybean crop, starting from: (i) requirements of the soybean crop towards environmental and technological factors so that it can effectively compete with weeds; (ii) reporting the weed control strategy to new climatic conditions through specific measures of adaptation; (iii) strategies research of chemical complementary herbicides regarding their combat range and time of application. In order to maintain soybean cultures clean of weeds, it is necessary, in general, to apply two chemical treatments, the first ppi/pre-emergent spraying for some annual dicotyledonous and monocotyledonous weeds and the 2nd post-emergence treatment for dicotyledonous weeds. If on vegetation exists infestations both with annual or perennial monocotyledonous weeds, good results are obtained by associating two complementary herbicides, which combat both monocotyledonous and dicotyledonous weeds. The lowest degree of weed (7.5 weed/m2) was determined with the combination: Frontier Forte & Surdone & Pulsar & Stratos Ultra.

Phytotoxicity levels in a wet year in an experiment on maize sensitivity to herbicides

The phytotoxic effects of herbicides applied pre-, early post- and post-emergence were studied in maize in a herbicide sensitivity experiment were set up in Martonvásár and Törökszentmiklós. The herbicides were applied in normal and in double doses to 37 Martonvásár inbred lines and to six parental single crosses. The small-plot experiments were set up in two replications. The wet weather that followed the pre- and early post-emergence treatments promoted the appearance of phytotoxic symptoms on maize. The degree of phytotoxicity was recorded on the 14th day after post-emergence treatment and on the 14th and 28th days after the pre- and early postemergence treatments. Herbicides applied pre-emergence only caused slight symptoms on maize. Although the double dose increased the damage, it was still not more than 5% on average. The symptoms caused by herbicides applied in the early post-emergence stage were more intensive than those detected in the pre-emergence treatments. However, the damage caused by the double dose of isoxaflutol + thiencarbazone-methyl and by the split treatment with nicosulfuron remained below 10%. The symptoms became somewhat more severe at the 2nd scoring date. Among the post-emergence treatments the maize genotypes had the least tolerance of the mesotrione + nicosulfuron combination of active ingredients, where the double quantities resulted in 13–14% damage in average.

Response of glyphosate-resistant kochia (Kochia scoparia L. Schrad.) to alternative herbicides

Burton, N., Shirriff, S. W. and Beckie, H. J. 2014. Response of glyphosate-resistant kochia (Kochia scoparia L. Schrad.) to alternative herbicides. Can. J. Plant Sci. 94: 1407–1411. A greenhouse study was conducted to examine the response of glyphosate-resistant (GR) plus acetolactate synthase (ALS) inhibitor-resistant kochia to five post-emergence herbicide treatments commonly used to control the weed species in chemical fallow, cereals, or oilseed crops in western Canada. The treatments, which were applied to two GR kochia biotypes and one non-GR (susceptible) biotype, included the labeled rate of dicamba, dicamba/fluroxypyr, dicamba/diflufenzopyr, MCPA/bromoxynil, and glufosinate. Both GR and non-GR biotypes responded similarly to each of the herbicide treatments. Although both GR biotypes were sensitive to the herbicides, MCPA/bromoxynil was the most effective treatment in reducing shoot biomass 3 wk after application (99%), followed by glufosinate (91%) then the dicamba mixtures (82%). Dicamba alone only suppressed kochia biomass (76% reduction).

English

A field experiment was conducted during summer season of 2010 and 2011 at district seed farm, Kalyani under Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, to find out the effect of different post emergence herbicides on summer growing groundnut in new alluvial zone of West Bengal. All the herbicidal treatments as well as weed free check significantly increased the yield and yield attributing characters of groundnut and also reduce the weed population as well as weed biomass production as compared to un-weeded control. Post emergence application of quizalofop Ethyl at 100g a.i./ha was found better to control the weeds as compared to imizathapyr. Among the post-emergence herbicidal treatments pod yield, haulm yield and yield attributes of groundnut was found maximum with the treatment received post emergence application of quizalofop Ethyl at 100 g a.i. /ha. Among all the herbicidal treatments best results was obtained with pre-emergence application of pendimethalin at 1.0 Kg a.i./ ha along with one hand weeding and recorded highest pod yield (2675 Kg/ha), haulm yield (3123 Kg/ha), number of pods/plant (17.3), shelling % (71.3) and SMK % (91.4). This might be due to application of pendimethalin as a pre emergence, suppresses the weed growth at early stage of the crop as a result of better crop stand. Practices of weed control by chemical and /or mechanical gave the significantly better pod yield of groundnut as compared to un-weeded control and pod yield of groundnut was decreased even up to 26 to 47% in un-weeded condition. Among the herbicidal treatments maximum gross return (Rs.80550), net return (Rs.55937) and B:C ratio (3.27) were recorded in the treatment received pre-emergence application of pendimethalin at 1.0 Kg a.i./ ha along with one hand weeding.   Key words: Groundnut, herbicide, pre-emergence, post-emergence, yield, economics.

SWEET CORN CAROTENOID CONCENTRATIONS INFLUENCED BY HERBICIDE APPLICATIONS

Carotenoids serve antioxidant functions in plant photosynthetic processes, as well as in actions of disease reduction in mammalian systems. Lutein and zeaxanthin are important dietary carotenoids in suppressing aging eye diseases. Age-related macular degeneration now affects more than 1.75 million individuals in the US. Sweet corn (Zea mays var. rugosa) is one of only a few vegetable sources high in zeaxanthin. Mesotrione herbicide is currently labeled for selective pre- and post-emergence weed control in sweet corn production. Mesotrione competitively inhibits phytoene desaturase, a critical enzyme in carotenoid biosynthesis, which results in bleaching of leaf tissues in susceptible species and eventual plant death. Sweet corn is tolerant to mesotrione applications; however, differing sensitivity exists among genotypes. What remains unclear is the impact of mesotrione on carotenoid concentrations in mature sweet corn kernels following post-emergent applications to young corn plants. Our research objective was to measure mature kernel carotenoid concentrations in response to post-emergence applications of mesotrione to genotypes of different sensitivities. Post-emergence treatments included mesotrione applied alone, or in mixtures with the photosystem II inhibitor atrazine applied to corn plants of either 5-10 or 15-20 cm in height. Kernels were harvested from mature plants and measured for carotenoid concentrations. Mesotrione applied alone, or in mixtures with atrazine acted to increase concentrations of kernel antheraxanthin, lutein, and zeaxanthin in several sweet corn genotypes. Mesotrione applications resulted in greater pools of kernel carotenoids once the sweet corn genotypes overcame initial herbicidal photo-oxidative stress. This is the first report of herbicides directly up regulating a key biochemical pathway linked to the nutritional quality of a vegetable crop.