Weed-free Checks Research Articles

Management of Weeds in Maize by Sequential or Individual Applications of Pre- and Post-Emergence Herbicides

Weeds impose serious problems in maize (corn) production, resulting in reduced crop yields and lower profits for farmers. The adverse effects of weeds have been attributed to the competition with maize plants for light, water, and nutrients, which can result in reduced growth and yield of the crop. In this context, effective weed management is important to minimize the negative impact of weeds on maize production. This can be achieved through a combination of cultural, mechanical, and chemical control methods. The use of pre-emergence and post-emergence herbicides as sequential or individual applications of these herbicides can be an effective way to manage weeds in maize. Two consecutive field experiments were conducted in 2019 and 2020 in order to determine the efficacy of sequential and individual applications of Dimethenamid-P + Terbuthylazine and Isoxaflutole + Thiencarbazone methyl + Cyprosulfamide as pre- emergence. On the other hand, Mesotrione + Nicosulfuron and Dicamba + Nicosulfuron were used as post-emergence herbicides. The effects of the herbicides were also assayed on corn yield and related parameters. In this regard, we designed the experiment in a randomized complete block design with four replications. Accordingly, the effect of the herbicides varied according to the active ingredients of the herbicide and the weed species. In addition, the effectiveness of herbicides varied according to the assessment times. The lowest effect was found on E. crus-galli, which was obtained from Mesotrione + Nicosulfuron (MN) (35%) plots. Other herbicides showed high efficacy (95–100%). Concerning values of both years, the highest cob length, cob diameter, 1000-grain weight, and plant height were obtained in weed-free control plots and the highest grain yield was obtained in the control plots with weed-free checks as 12.88 tons/ha and 12.37 tons/ha, respectively. The lowest corn grain yield was obtained in weedy control plots in both years. Our findings demonstrate that the combination of pre- and post- emergence herbicides in maize can be an effective way chemical weed control option.

Safety and efficacy of linuron with or without an adjuvant or S-metolachlor for POST control of Palmer amaranth (Amaranthus palmeri) in sweetpotato

AbstractField studies were conducted to evaluate linuron for POST control of Palmer amaranth in sweetpotato to minimize reliance on protoporphyrinogen oxidase (PPO)-inhibiting herbicides. Treatments were arranged in a two by four factorial in which the first factor consisted of two rates of linuron (420 and 700 g ai ha−1), and the second factor consisted of linuron applied alone or in combinations of linuron plus a nonionic surfactant (NIS; 0.5% vol/vol), linuron plus S-metolachlor (800 g ai ha−1), or linuron plus NIS plus S-metolachlor. In addition, S-metolachlor alone and nontreated weedy and weed-free checks were included for comparison. Treatments were applied to ‘Covington’ sweetpotato 8 d after transplanting (DAP). S-metolachlor alone provided poor Palmer amaranth control because emergence had occurred at applications. All treatments that included linuron resulted in at least 98% and 91% Palmer amaranth control 1 and 2 wk after treatment (WAT), respectively. Including NIS with linuron did not increase Palmer amaranth control compared to linuron alone, but it resulted in greater sweetpotato injury and subsequently decreased total sweetpotato yield by 25%. Including S-metolachlor with linuron resulted in the greatest Palmer amaranth control 4 WAT, but increased crop foliar injury to 36% 1 WAT compared to 17% foliar injury from linuron alone. Marketable and total sweetpotato yields were similar between linuron alone and linuron plus S-metolachlor or S-metolachlor plus NIS treatments, though all treatments resulted in at least 39% less total yield than the weed-free check resulting from herbicide injury and/or Palmer amaranth competition. Because of the excellent POST Palmer amaranth control from linuron 1 WAT, a system that includes linuron applied 7 DAP followed by S-metolachlor applied 14 DAP could help to extend residual Palmer amaranth control further into the critical period of weed control while minimizing sweetpotato injury.

Effect of post-emergence herbicides in chickpea

A field experiment was conducted during two consecutive (Rabi) winter seasons (2018-19 and 2019-20) at Agricultural Research Station, Navgaon (Alwar), S.K.N. Agriculture University, Jobner, Jaipur (Rajasthan), India, to study the effect of weed management practices in chickpea. The experiment was laid out in a randomized block design with eight treatments and replicated thrice. The crop was sown as per the package of practices recommended for zone IIIB of Rajasthan. Treatments included application of pendimethalin 30% EC 1.0 kg/ha as pre-emergence, and quizalofop-p-ethyl 10% SL at 50g/ha, fenoxaprop p-butyl 10% EC at 100 g/ha, imazethapyr 10% EC at 75 g/ha, imazethapyr (35%) + imazamox (35%) at 100 g/ha, imazethapyr (2%) + pendimethalin (30%) at 2.5 litre/ha as post-emergence along with weedy and weed free checks. Among the different herbicidal treatments, imazethapyr (35%) + imazamox (35%) at 100 g/ha recorded significantly higher seed yield 2.22 t/ha in 2018-19 and 2.28 t/ha in 2019-20 with higher weed control efficiency and the lowest weed index. However, it remained at par with imazethapyr 10% EC 75 g/ha and, imazethapyr (2%) + pendimethalin (30%) at 1.0 kg/ha.

Effect of weeding frequency and interval on onion (Allium cepa L.) bulb yield grown under irrigation condition at Arba Minch, Southern Ethiopia

Field experiment was conducted at Arba Minch during 2017 and 2018 cropping seasons under irrigation condition to determine the effect of weeding frequency and interval on weeds and bulb yield of onion. The experiment was laid out in factorial arrangement in randomized complete block design with three replications and comprised of 18 treatments: four weeding frequencies (2, 3, 4 and 5 times) and four weeding intervals (at 10, 13, 17 and 25 days) compared with weedy and weed-free checks. Results showed that all the parameters considered in this study were significant (p<0.05) among the treatments. The lowest weed density (27.33 m-2 in 2017 and 24.26 m-2 in 2018) and dry weed biomass weight (0.83 t ha-1 in 2017 and 0.82 t ha-1 in 2018) were recorded in the weed free check without statistical difference with the values received from weeding interval at 10, 13 and 17 for four and five times weeding frequency in both cropping seasons. The highest weed control efficiency (83.70% in 2017 and 82.82% in 2018) was computed in the weed free plots. In the 2017 cropping season, the highest marketable bulb yield (32.8 t ha-1) was recorded in the weed free check, which was statistically similar with the result obtained in four and five times weeding frequency at 10, 13 and 17 days weeding interval. Similar trends were observed during 2018 cropping season. Thus, three to five times frequency of weeding at 10 days weeding interval could be recommended in the study area for efficient weed management and optimization of the bulb yield and profits in onion production.

Response of Palmer Amaranth and Sweetpotato to Flumioxazin/Pyroxasulfone

AbstractStudies were conducted to determine the tolerance of sweetpotato and Palmer amaranth control to a premix of flumioxazin and pyroxasulfone pretransplant (PREtr) followed by (fb) irrigation. Greenhouse studies were conducted in a factorial arrangement of four herbicide rates (flumioxazin/pyroxasulfone PREtr at 105/133 and 57/72 g ai ha–1,S-metolachlor PREtr 803 g ai ha–1, nontreated) by three irrigation timings [2, 5, and 14 d after transplanting (DAP)]. Field studies were conducted in a factorial arrangement of seven herbicide treatments (flumioxazin/pyroxasulfone PREtr at 40/51, 57/72, 63/80, and 105/133 g ha–1, 107 g ha–1flumioxazin PREtr fb 803 g ha–1S-metolachlor 7 to 10 DAP, and season-long weedy and weed-free checks) by three 1.9-cm irrigation timings (0 to 2, 3 to 5, or 14 DAP). In greenhouse studies, flumioxazin/pyroxasulfone reduced sweetpotato vine length and shoot and storage root fresh biomass compared to the nontreated check andS-metolachlor. Irrigation timing had no influence on vine length and root fresh biomass. In field studies, Palmer amaranth control was≥91% season-long regardless of flumioxazin/pyroxasulfone rate or irrigation timing. At 38 DAP, sweetpotato injury was≤37 and≤9% at locations 1 and 2, respectively. Visual estimates of sweetpotato injury from flumioxazin/pyroxasulfone were greater when irrigation timing was delayed 3 to 5 or 14 DAP (22 and 20%, respectively) compared to 0 to 2 DAP (7%) at location 1 but similar at location 2. Irrigation timing did not influence no.1, jumbo, or marketable yields or root length-to-width ratio. With the exception of 105/133 g ha–1, all rates of flumioxazin/pyroxasulfone resulted in marketable sweetpotato yield and root length-to-width ratio similar to flumioxazin fbS-metolachlor or the weed-free checks. In conclusion, flumioxazin/pyroxasulfone PREtr at 40/51, 57/72, and 63/80 g ha–1has potential for use in sweetpotato for Palmer amaranth control without causing significant crop injury and yield reduction.

Evaluation of the Efficacy of Some Pre-Emergence Herbicides in Cotton (<i>Gossypium Spp.</i>) in Northern Ghana

A field experiment was conducted at the Savanna Agricultural Research Institute to investigate the effects of pre-emergence herbicides for weed control in cotton during the 2014 and 2015 cropping seasons. The study determined the effects of different rates of three novel cotton herbicides with different formulations on weeds, yield components and yield of seed cotton, applied as pre-emergence. The treatments were laid out in randomized complete block design with four replications and consisted of Diflufenican + Flufenicent and Diflufenican + Flufenicent + Flurtamone as 500SC formulations of each and applied at the rate of 0.3, 0.4, 0.6, and 0.8 l/ha, whilst Diflufenican + Flufenicent + Flurtamone as 200SC formulation was applied at 0.4, 0.5, 0.8, and 1.0L/ha. A reference herbicide + product with active ingredients Promotrin + Metolachlor applied at 3.0l /ha and untreated weedy and weed free checks were included. Results showed that. Diflufenican + Flufenicent + as 200SC applied at 0.8 l/ha gave the lowest weed dry weight (65.0 g/m2) similar to the reference herbicide (189.4 g/m2) and Diflufenican + Flufenicent + Flurtamone as 200SC applied at 0.8 l/ha (144.8 g/m2), whilst weedy check gave highest (548.7 kg/m2). Consequently, Diflufenican+ Flufenicent applied at 0.8 l/ha gave significantly (p<0.05) the highest number of bolls and number of opened bolls than the reference herbicide; but similar to weed free. Diflufenican + Flufenicent +Flurtamone as 500SC, applied at 1.0 l/ha supported tallest plants similar to Diflufenican + Flufenicent + Flurtamone as 200SC at 0.4 and 0.6 l/ha and Diflufenican + Flufenicent as 500SC applied at 0.6 and 0.8 l/ha and better than the reference herbicide. Diflufenican+ Flufenicent as 500SC applied at 0.8L/ha (81.3 %), Diflufenican + Flufenicent + Flurtamone as 500SC at 0.8 l/ha (78.7 %) and the reference herbicide (76.3 %) did better (90 %) than weed free. Generally, early control of weeds with the tested herbicides using 0.4 to 1.0 l/ha minimized weed growth and supported high seed cotton yields.

Influence of Integrated Weed Management Practices on Weed Dynamics, Yield Components and Yield of Faba bean (Vicia faba L.) in Eastern Ethiopia

The experiment was conducted to assess the integrated effects of pre-emergence herbicides and hand-weeding on weed control, yield components and yield of Faba bean to assess their economic feasibility for cost effective weed control in Faba bean. The experiment consisted of 12 treatments viz. pre emergence S-metolachlor and Pendimethalin each at three rates S-metolachlor+one-hand-weeding, pendimethalin+one-hand-weeding, two-handweeding, complete weed free and weedy checks arranged in randomized complete block design with three replications. The weed flora consisted of broadleaved and sedge with the relative densities of 81.02 and 18.98% at Haramaya, and 80.83% and 19.17%, at Gurawa, respectively. Application of S-metolachlor and Pendimethalin 1.0 kg ha-1 each supplemented with hand weeding 5 WAE significantly (p ≤ 0.01) affected the broadleaved weeds, sedges and weed dry weight at both sites. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE gave the lowest total number of weeds (8.29 m-2) following the weed free check. Higher grain yield (3555.8 kg ha-1) was produced with S-metolachlor 1.0 kg ha-1 supplemented with one-hand-weeding 5 WAE following complete weed-free at Gurawa. The benefit gained from S-metolachlor and Pendimethalin at 1.0 kg ha-1 each supplemented with one hand weeding 5 WAE were greater than the value recorded from the weedy check by 216% and 198%, respectively. S-metolachlor 1.0 kg ha-1 supplemented with hand weeding 5 WAE treatment resulted in the highest grain yield and economic benefit. However, in case labour is constraint and S-metolachlor herbicide is timely available, pre emergence application of s-metolachlor at 2.0 kg ha-1 should be the alternative to preclude the yield loss and to ensure maximum benefit.

Weed suppression and soybean yield in a no-till cover-crop mulched system as influenced by six rye cultivars

AbstractCover crop mulches have been successful in reducing weed severity in organic soybeans. This study examined six rye cultivars (SRCs) used as cover crops to determine which were most adapted for use with a roller–crimper in the southeastern U.S. To be an effective mulch, a rye cultivar must produce high biomass and reach reproductive growth stage to facilitate mechanical termination via the roller–crimper prior to soybean planting. Rye cultivars were planted at three locations in North Carolina over the 2009 and 2010 growing seasons. Each rye cultivar was mechanically terminated via a roller–crimper implement. Rye cover crops were terminated on two dates and soybeans were immediately no-till planted into the mulch. In 2009, all rye cultivars produced greater than 9000 kg ha−1 rye biomass dry matter (DM) with the exception of Rymin at Plymouth (2009), but in 2010 only the early flowering cultivars produced in excess of 9000 kg ha−1 DM. There were no detectable soybean yield differences between the SRCs and the weed-free checks, and weed control was excellent across all SRCs at both Plymouth and Salisbury (2009). After an unseasonably cold and wet winter in 2010, the late flowering rye cultivars were not fully controlled by the early termination date due to delayed maturation (less than 65% control at 2 WAP) whereas the early flowering cultivars were fully controlled (100% control at 2 WAP). Rye biomass production was below 9000 kg ha−1 DM for the late flowering and dough development rye cultivars. The early-terminated rye plots had greater weed coverage across all SRCs than those from the late termination date (P < 0.01). However, weeds did not impact soybean yield for either of the termination dates. Soybean yield in 2010 was modeled with rye biomass and soybean population used as covariates, and for both termination dates, soybean yield was proportional to rye biomass production. Early flowering rye cultivars offer producers the widest range of termination opportunities that best coincide with their cash crop planting dates.

Controle de Urochloa plantaginea com herbicidas residuais e performance agronômica de dois cultivares de feijoeiro

O objetivo deste trabalho foi avaliar os efeitos da utilização de herbicidas residuais, aplicados em pré-emergência do feijoeiro, sobre a redução da infestação de plantas daninhas e o desempenho agronômico da cultura. Foram realizados dois experimentos a campo, sendo que um tinha o cultivar UFT -06 (Grupo Carioca, ciclo curto e porte ereto) e o outro o cultivar IPR Graúna (Grupo Preto, ciclo longo, hábito prostrado). Os tratamentos foram constituídos da aplicação dos herbicidas pendimethalin (1,2 e 1,4 kg ha-1) e trifluralin (1,2 e 1,4 kg ha-1); e, dimethenamid (1,4 e 1,6 kg ha-1) e S-metolachlor (1,4 e 1,6 kg ha-1), e mais testemunha com e sem (TSC) controle. Nas áreas experimentais predominavam infestação de Urochloa plantaginea (papuã). Avaliou-se a densidade e a massa desta espécie daninha, e o número de legumes e a produtividade do feijoeiro. Trifluralin foi o herbicida que mais reduziu a infestação da planta daninha e aumentou o rendimento do feijoeiro, quando comparado aos demais produtos. O cv. de feijão UTF-06 foi mais competitivo com U. plantaginea do que IPR Graúna. Os tratamentos com herbicida reduziram a infestação da infestante, mas isso não resultou em maior produtividade do feijoeiro, quando comparado com o tratamento capinado.

Control of herbicide-resistant common waterhemp (Amaranthus tuberculatus var. rudis) with pre- and post-emergence herbicides in soybean

Common waterhemp was first identified in Ontario in 2002. Eight trials were conducted ove r a 3-yr period (2003-2005) at Cottam and Petrolia, Ontario to determine the efficacy of various preemergence and postemergence herbicides for the control of herbicideresistant waterhemp in soybean [ Glycine max (L.) Merr.]. Waterhemp was resistant to the a cetolactate synthase-inhibiting herbicides at both locations and to the photosystem II-inhibiting herbicides at Petrolia; therefore, results varied by location. Results at Petrolia also varied across years. Waterhemp interference resulted in soybean yield losses of up to 73% in weedy versus weed-free checks. Preemergence-applied metolachlor, dimethenamid, and linuron provided greater than 80% control and metolachlor plus metribuzin 94% or greater control of waterhemp 70 d after emergence at both locations. Acifluorfen, fomesafen, imazamox plus fomesafen, and glyphosate applied postemergence resulted in 87% or greater waterhemp control 70 d after application at Cottam in 2003 and 2004 and at Petrolia in 2004; however, waterhemp control with these herbicides was only 60 to 66% at Petrolia in 2005 due to prolonged weed emergence. Multiple herbicide applications per season may be required for effective waterhemp control in soybean. Key words:

Practical Changes to Single-Boom Sprayers for Zone Herbicide Application

Reduced-rate zone herbicide application (ZHA) consists of banding reduced herbicide rates between crop rows (≤ full broadcast registered rate, 1×) and banding much reduced herbicide rates over crop rows (≪ 1×). The objective of this research was to compare the mechanically complicated dual-boom ZHA sprayer with a much simpler, single-boom ZHA sprayer for controlling giant foxtail and common waterhemp in field corn in 2003 and 2004 in Missouri. The dual-boom ZHA sprayer employed two different herbicide solutions, which were propelled through two booms on separate sprayer systems to apply different herbicide rates over in-row and between-row areas while maintaining similar carrier volumes and coverage through two booms. In contrast, the single-boom ZHA sprayer is a mechanically simpler system in which both herbicide rates and carrier volumes were varied across one boom over in-row (IR) and between-row (BR) areas. In single-boom ZHA, two different nozzle tips were alternated on one boom over in-row and between-row areas, the number of nozzles per boom was doubled, and the distance between nozzles was halved compared with a conventional sprayer boom. In a 2-yr study, these different ZHA sprayers were used to apply preemergence atrazine + S-metolachlor between and over crop rows at various reduced rates (1× = 2,240 + 1,750 g ai/ha, respectively). Among all single- and dual-boom ZHA sprayer treatments and the weed-free checks, corn yields and in-row total weed cover were statistically indistinguishable for both years and for between-row total weed cover in 1 of 2 yr. In both years, a single-boom ZHA system prevented yield loss from competing weeds as effectively as the dual-boom ZHA system. The new single-boom ZHA system is a mechanically simple, inexpensive, generic alternative for reducing herbicide rates and lowering input costs.

Critical Weed-Free Period for ‘Beauregard’ Sweetpotato (Ipomoea batatas)1

Studies were initiated at two different planting dates and conducted at two different locations in 2001 to determine the critical weed-free period for certain populations of weeds in organically produced ‘Beauregard’ sweetpotato. Naturally occurring weed populations were used, and they included sicklepod, redroot pigweed, and yellow nutsedge. Treatments included allowing weeds to grow for 2, 4, 6, or 8 wk after transplanting (WAT) sweetpotato before weed removal and maintaining the sweetpotato weed-free for 2, 4, 6, or 8 WAT. Weedy and weed-free checks were also included in the study. These treatments were used to determine the length of time weeds can compete with sweetpotato without reducing yield and the length of time sweetpotato must grow before yield is no longer affected by newly emerging weeds. Yield of number one grade sweetpotato roots best fit a quadratic plateau curve for the grow-back treatments and a logistic curve for the removal treatments. Yields in weed-free plots of sweetpotato were higher at the early planting date, whereas yields in plots of weedy sweetpotato were higher at the late planting date. Weed biomass was lower in the grow-back treatments at the late planting date. Data indicate that sweetpotato may gain a competitive advantage over weeds when planted at a later date. At both planting dates, a critical weed-free period of 2 to 6 WAT was observed.Nomenclature: Redroot pigweed, Amaranthus retroflexus L. #3 AMARE; sicklepod, Senna obtusifolia (L.) Irwin and Barneby # CASOB; yellow nutsedge, Cyperus esculentus L. # CYPES; sweetpotato, Ipomoea batatas (L.) Lam. ‘Beauregard’.Additional index words: Competition, interference, organic production, Brachiaria platyphylla, Eleusine indica, Mollugo verticillata, Sida spinosa, BRAPP, ELEIN, MOLVE, SIDSP.Abbreviations: WAT, weeks after transplanting.

Influence of tank mixture of herbicides on weed control in upland cotton (Gossypium hirsutum)

A field study was carried out at ,Hisar tion) @ 1.50 kgha significantly reduced the during the rainy season of 1990 and 1991. population and dry weight of total weeds at The soil was low in nitrogen, medium in 60 days after sowing compared with the phosphorus and high in potassium. H 777 weedy check (Table 1). Combination of upland cotton (Gossypium hirsutum L.) was these herbicides in a ratio of 1 : 1 did not sown on 26 May 1990 and 17 May 1991. improve the control of weeds compared All the other cultural practices were fol- with their sole treatments. The dry weight lowed in accordance with the local package of total weeds in plots where fluchloralin of practices. The experiment was laid out in was used alone or as tank mixture with randomized block design with 3 replica- oxadiazon was less than when higher dose tions. The treatments used were: oxadiazon of pendimethalin or oxadizon or their mix- @ 0.75 and 1 .OO kglha, pendimethalin @ ture. The seed-cotton yields under the treat- 1.00 and 1.50 kglha and oxadiazon + ment of pendimethalin or fluchloralin or pendimethalin @ 0.50 + 0.50 kgha and their mixture or oxadiazon @ 1.0 kglha or 0.75 + 0.75 kgha (applied pre-emergence), oxadiazon + fluchloralin @ 0.75 + 0.75 kg1 while fluchloralin @ 1.00 and 1.50 kglha, ha were significantly more than that under fluchloralin + pendimethalin @ 0.50 + 0.50 the weedy check. The maximum seed-cotton kgoa and $75 + 0.75 kglha and oxadiazon yield was registered with weed-free check + fluchloralin @ 0.50 + 0.50 and 0.75 + but remained on a par with pendimethalin 0.75 kgha (applied as pre-plant incorpora- applied. @ 1.50 kglha at pre-emergence tion) with weedy and weed-free checks. All stage (Table 1). Similar results were re- the herbicides were applied by knap-sack ported by Balyan et al. (1983) with sprayer using 650 litres waterha. Weed pendimethalin or fluchloralin and Panwar et counts (No./m2) and dry weight of total al. (1989) with oxadiazon. weeds (g/m2) were recorded at 60 days after REFERENCES sowing by using 0.50 m x 0.50 m quadrat. Balyan, R. S., Bhan, V. M. and Singh, S. P. 1983. The dominant weeds identified were: carpet Chemical and cultural weed control in cotton. weed (Trianthema portulacastrum L.) and Tropical Pest Management 29 : 56-59. nut sedge (Cyprus rotundus L.). - Panwar, R. S., Malik, R. K., Bhan, V. M. and Malik, Pendimethalin (pre-emergence) @ 1.50 R. S. 1989. Evaluation of pre-emergence kglha or oxadiazon pre-emergence @ 1.50 and postemergence herbicides in cotton. Jnurnal ($Research, Haryana Agricultural University. kglha or fluchloralin (pre-plant incorpora- Hisar 19 : 235-239.

Pinoxaden: an alternate herbicide against littleseed canary grass (Phalaris minor) in wheat (Triticum aestivum) DHARAM BIR YADAV1, S.S. PUNIA* , ASHOK YADAV*, SAMUNDER SINGH* AND ROSHAN LAL

Two field experiments were conducted at Karnal, Haryana daring rabi 2005-06 and 2006-07 to evaluate the efficacy of pinoxaden against Phalaris minor in wheat. Pinoxaden 10 EC 40 g/ha + adjuvant 2,000 ml/ha and pinoxaden 5 EC (with built-in adjuvant) 50 g/ha reduced the dry weight of Phalaris minor to the extent of 92-99 and 89-98?,, respectively, and were at par with weed free checks during both the years. Consequently, Pinoxaden 5 EC 50 g/ha and Pinoxaden 10 EC 40 g/ha + adjuvant 2,000 mVha being at par with weed free checks produced grain yield of wheat to the tunne of 6.1-6.2 and 5.7-6.1 t/ha. Efficacy of pinoxaden 10 EC against P minor increased by about 70% with addition of adjuvant indicating that adjuvant is must with this for- . mulation. Pinoxaden 5 EC 50 g/ha was superior to lower doses, fenoxaprop and sulfosulfuron, however, it was at par with clodinafop during both the years. Both formulations of pinoxaden were ineffective against broad-leaved weeds. Maximum net returns (Rs 14,400-19,50O/ha) and benefit: cost ratio (0.74-0.91) was obtained under pinoxaden 5 EC 50 g/ha. There was no phytotoxicity on wheat and no residual toxicity on the succeeding rice crop.

Postemergence Control of Phyllanthus urinaria by Prodiamine and Phytotoxicity to Ornamentals

Postemergence control of Phyllanthus urinaria L. (chamberbitter) in nursery and landscape plantings has been primarily limited to hand-weeding. Prodiamine was evaluated for postemergence control of chamberbitter and phytotoxicity to containerized ornamentals. On 20 June 1995, prodiamine at 0, 1.68, 3.36, or 6.72 kg a.i./ha was applied over-the-top to immature chamberbitter growing in 3.8-L containers of established Buddleia davidii Franch. `White Bouquet' Cuphea hyssopifolia HBK. `Desert Snow', Lantana camara L. `Irene', and Lantana montevidensis (Spreng.) Briq. `Lavender Weeping'. Weed-free checks were included. Applications were made with a compressed air backpack sprayer. There were four replications per treatment placed in a randomized complete block design by species. Plants were established and maintained on a container bed under full sun and overhead irrigation. Growth of and phytotoxicity to the ornamentals species, and percent coverage and number of chamberbitter, were recorded periodically for 14 weeks after treatment (WAT). Chamberbitter shoots were harvested for dry weight analysis 14 WAT. Prodiamine provided some postemergence control of chamberbitter. However, Cuphea and both Lantana species exhibited leaf distortion and/or delayed flowering.

Avaliação da eficiência do herbicida sulfentrazone no controle da tiririca, na cultura da cana-de-açúcar

O presente trabalho foi conduzido com o objetivo de avaliar a eficiência do herbicida sulfentrazone no controle de tiririca (Cyperus rotundus L.) e a sua seletividade na cultura da cana-de-açúcar. O ensaio foi instalado no município de Santa Bárbara do Oeste - São Paulo. O solo da áre a experimental apresenta textura leve, sendo classificado como Podzólico Vermelho Amarelo. A variedade utilizada foi RB 76-5418, plantada dia 13/01/94. 0 delineamento experimental foi de blocos ao acaso com quatro repetições. A aplicação foi feita com um pulver izador cos tal pre ssur izado a CO2, com pressão de trabalho de 2,106 kg/cm2 (30 psi), equipado com bicos de jato plano do tipo Teejet 11 00 3 XR e com consumo de cald a de 300 litros/ha. A operação foi realizada no dia 20 de janeiro de 1994 , com so lo úmido e em pré emergência da cultura e das plantas daninhas. Os tratamentos utilizados foram: testemunha sem capina; testemunha capinada; sulfentrazone aplicado nas doses de 500, 600, 700, 800:900 e 1000g i.a./ha. A tiririca foi a planta daninha predominante na área, alcançando 312 manifestações epígeas/m2 aos 30 dias após aplicação. Avaliou-se a eficiência, a intensidade das injúrias provocadas e várias características referentes ao cres cimento e produtividade da cultura. Verificou-se que o herbicida sulfentrazone apresentou bom controle da tiririca em doses iguais ou superiores a 800g i.a./ha. Em todas as doses o herbicida foi seletivo à cultura de cana-de-açúcar, não afetando a altura de plantas, o estande, a produtividade e a qualidade industrial dos colmos obtidos.

Growth and Development of Florida Beggarweed (Desmodium tortuosum) Selections

Florida beggarweed seeds were collected in Georgia, Florida, and South Carolina from plants differing in morphological characteristics. Seedlings were transplanted into peanut rows in field studies at Tifton, GA, and Jay, FL, in 1986 and 1987, and frequent observations of vegetative and reproductive characteristics were made. The competitiveness of the Florida beggarweed selections was evaluated by comparing pod weights from peanut plants grown in rows adjacent to the individual weed selections with pod weights of weed-free peanuts. There were significant differences among selections of Florida beggarweed in days to maximum height, maximum node formation, maximum branching, and initial flowering and fruiting at both locations. Selection GA-1 generally reached these growth stages earliest, was shorter, narrower, had fewer nodes, and produced less dry matter and fewer seeds than GA-2, which was generally the latest maturing selection. GA-4 produced fewer branches and smaller seeds than the other selections. Peanut pod weights adjacent to Florida beggarweed plants were reduced 12 to 18% in 1986 and 10 to 24% in 1987 compared to weed-free checks. Florida beggarweed selection GA-2 was the most competitive and GA-4 was among the least competitive both years. The variation of measured parameters among Florida beggarweed selections in this study may contribute to the survival and adaptability of this weed with changing environmental conditions, cultural practices, and control measures.

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).

Response of Prickly Sida and Soybeans to Various Herbicides

Three preemergence and four postemergence herbicides were compared for control of prickly sida (Sida spinosaL.) in soybeans (Glycine maxMerrill) and for level of phytotoxicity to soybeans. As a preemergence herbicide, chlorbromuron [3-(4-bromo-3-chlorophenyl)-1-methoxyl-1-methylurea] provided better control of prickly sida than did linuron [3-(3,4-dichlorophenyl)-1-methoxyl-1-methylurea] which was more consistently effective than was naptalam (N-1-naphthylphthalamic acid) plus dinoseb (2-sec-butyl-4,6-dinitrophenol). Chlorbromuron applied as a preemergence treatment caused slight crop injury. In most cases preemergence treatments followed by cultivation were effective in providing season-long control. The descending order of effectiveness for prickly sida control by the postemergence herbicides was: chlorbromuronmetribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] > prometryne [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] > dinoseb. Prometryne as a postemergence treatment following a preemergence herbicide increased prickly sida control more consistently than dinoseb used as the postemergence treatment. However, prometryne caused more crop injury than did dinoseb.Comparison of soybean yields from the weedy and weed free checks show that prickly sida caused only 9 to 14% yield losses in soybeans.